{"version":"1.0.0","segments":[{"startTime":0.69,"endTime":3.9,"body":"- This lecture is part of"},{"startTime":0.69,"endTime":3.9,"body":"a series of six lectures"},{"startTime":3.9,"endTime":7.623,"body":"on how technology is changing"},{"startTime":3.9,"endTime":7.623,"body":"the world of finance."},{"startTime":8.64,"endTime":10.56,"body":"This is the second in that lecture,"},{"startTime":10.56,"endTime":12.843,"body":"and it's about love, trust, and crypto."},{"startTime":13.77,"endTime":18.45,"body":"Now, many of you may think"},{"startTime":13.77,"endTime":18.45,"body":"these topics don't go together."},{"startTime":18.45,"endTime":19.98,"body":"Love, crypto."},{"startTime":19.98,"endTime":22.77,"body":"But I'll try to convince you"},{"startTime":19.98,"endTime":22.77,"body":"that is the essential part"},{"startTime":22.77,"endTime":26.1,"body":"of trust and love and crypto."},{"startTime":26.1,"endTime":28.47,"body":"But before we actually go through that,"},{"startTime":28.47,"endTime":31.44,"body":"let me talk a little bit"},{"startTime":28.47,"endTime":31.44,"body":"about the way society"},{"startTime":31.44,"endTime":34.563,"body":"has evolved over the past 300 years."},{"startTime":36.3,"endTime":39.36,"body":"Let's go back to the"},{"startTime":36.3,"endTime":39.36,"body":"pre-industrial revolution period,"},{"startTime":39.36,"endTime":41.28,"body":"This is before 1750."},{"startTime":41.28,"endTime":44.64,"body":"Most people are living in small villages."},{"startTime":44.64,"endTime":47.73,"body":"They don't travel, they"},{"startTime":44.64,"endTime":47.73,"body":"just hang out in villages."},{"startTime":47.73,"endTime":51.75,"body":"They farm, they have local activities."},{"startTime":51.75,"endTime":55.59,"body":"But most people are born,"},{"startTime":51.75,"endTime":55.59,"body":"grow up and they die"},{"startTime":55.59,"endTime":57.57,"body":"in pretty much the same area."},{"startTime":57.57,"endTime":59.04,"body":"If you're especially adventurous,"},{"startTime":59.04,"endTime":63.033,"body":"maybe you go to a nearby town,"},{"startTime":59.04,"endTime":63.033,"body":"but most people don't travel."},{"startTime":63.9,"endTime":67.17,"body":"Things changed in the 1750s."},{"startTime":67.17,"endTime":69.993,"body":"What happened was the"},{"startTime":67.17,"endTime":69.993,"body":"industrial revolution."},{"startTime":71.34,"endTime":74.28,"body":"We had James Watt"},{"startTime":71.34,"endTime":74.28,"body":"inventing the steam engine."},{"startTime":74.28,"endTime":77.94,"body":"Richard Arkwright, the"},{"startTime":74.28,"endTime":77.94,"body":"Jenny, and people like that"},{"startTime":77.94,"endTime":80.643,"body":"basically mechanized the"},{"startTime":77.94,"endTime":80.643,"body":"process of production."},{"startTime":81.84,"endTime":83.67,"body":"Now, most people don't realize this."},{"startTime":83.67,"endTime":87.48,"body":"You don't actually need"},{"startTime":83.67,"endTime":87.48,"body":"to mechanize production"},{"startTime":87.48,"endTime":88.92,"body":"if you don't have scale."},{"startTime":88.92,"endTime":91.53,"body":"For example, you don't"},{"startTime":88.92,"endTime":91.53,"body":"need a spinning Jenny"},{"startTime":91.53,"endTime":93.453,"body":"if your entire production,"},{"startTime":96.606,"endTime":98.82,"body":"all your customers are"},{"startTime":96.606,"endTime":98.82,"body":"based in one village,"},{"startTime":98.82,"endTime":101.37,"body":"the fixed costs are just too high."},{"startTime":101.37,"endTime":103.35,"body":"In order for this to be worthwhile,"},{"startTime":103.35,"endTime":105.3,"body":"you need to expand your customer base."},{"startTime":105.3,"endTime":106.923,"body":"You need to have scale up."},{"startTime":108.36,"endTime":109.65,"body":"How do you scale up?"},{"startTime":109.65,"endTime":112.92,"body":"Well, you try to produce more and more,"},{"startTime":112.92,"endTime":117.69,"body":"in order to overcome the"},{"startTime":112.92,"endTime":117.69,"body":"fixed cost of setting up"},{"startTime":117.69,"endTime":119.76,"body":"a weaving room or a steam engine,"},{"startTime":119.76,"endTime":121.5,"body":"and things like that."},{"startTime":121.5,"endTime":124.86,"body":"But to increase that"},{"startTime":121.5,"endTime":124.86,"body":"size, increase the scale,"},{"startTime":124.86,"endTime":126.69,"body":"you need to hire people."},{"startTime":126.69,"endTime":128.13,"body":"Where do you get those people?"},{"startTime":128.13,"endTime":129.96,"body":"Well, it doesn't work within the village."},{"startTime":129.96,"endTime":133.71,"body":"You move to towns, you hire"},{"startTime":129.96,"endTime":133.71,"body":"people from the local villages,"},{"startTime":133.71,"endTime":136.77,"body":"and some of these guys,"},{"startTime":133.71,"endTime":136.77,"body":"they may know each other,"},{"startTime":136.77,"endTime":139.14,"body":"but many of them have"},{"startTime":136.77,"endTime":139.14,"body":"don't know each other."},{"startTime":139.14,"endTime":140.22,"body":"Maybe you come from one village,"},{"startTime":140.22,"endTime":141.87,"body":"maybe you know the people in that village"},{"startTime":141.87,"endTime":143.97,"body":"who started working in that factory,"},{"startTime":143.97,"endTime":145.803,"body":"but you don't know anybody else."},{"startTime":146.97,"endTime":149.403,"body":"Anyway, in the 1840s, it became bigger."},{"startTime":150.33,"endTime":152.73,"body":"That was the introduction"},{"startTime":150.33,"endTime":152.73,"body":"of electrical energy."},{"startTime":152.73,"endTime":157.73,"body":"And once you have electrical"},{"startTime":152.73,"endTime":157.73,"body":"energy, you need more capital."},{"startTime":157.77,"endTime":160.47,"body":"To have more capital, in"},{"startTime":157.77,"endTime":160.47,"body":"order to make a profit,"},{"startTime":160.47,"endTime":162.93,"body":"you have to increase the"},{"startTime":160.47,"endTime":162.93,"body":"scale of production again."},{"startTime":162.93,"endTime":164.55,"body":"So you need to hire more people"},{"startTime":164.55,"endTime":167.58,"body":"in order to produce more and more goods."},{"startTime":167.58,"endTime":169.47,"body":"You have to have a bigger customer base."},{"startTime":169.47,"endTime":172.2,"body":"That was, in a sense, what"},{"startTime":169.47,"endTime":172.2,"body":"the British Empire did."},{"startTime":172.2,"endTime":176.19,"body":"You had massive customer bases"},{"startTime":172.2,"endTime":176.19,"body":"all over the British Empire,"},{"startTime":176.19,"endTime":178.68,"body":"but everything was driven"},{"startTime":176.19,"endTime":178.68,"body":"by the fact you were trying"},{"startTime":178.68,"endTime":180.81,"body":"to make your your"},{"startTime":178.68,"endTime":180.81,"body":"processes more efficient,"},{"startTime":180.81,"endTime":183.243,"body":"to go to a bigger and bigger scale."},{"startTime":184.08,"endTime":186.03,"body":"That's when assembly"},{"startTime":184.08,"endTime":186.03,"body":"lines were introduced."},{"startTime":186.03,"endTime":188.49,"body":"That's when mass production"},{"startTime":186.03,"endTime":188.49,"body":"techniques were introduced."},{"startTime":188.49,"endTime":191.163,"body":"All of this happened till about 1920."},{"startTime":192.06,"endTime":194.01,"body":"But the human consequences were bigger."},{"startTime":195.33,"endTime":199.71,"body":"If you are, for example,"},{"startTime":195.33,"endTime":199.71,"body":"somebody who's working"},{"startTime":199.71,"endTime":200.79,"body":"in one of these,"},{"startTime":200.79,"endTime":205.26,"body":"you're moving from a village"},{"startTime":200.79,"endTime":205.26,"body":"to a town, to a city now,"},{"startTime":205.26,"endTime":208.68,"body":"and people from all over the"},{"startTime":205.26,"endTime":208.68,"body":"country are in that city."},{"startTime":208.68,"endTime":210.9,"body":"They're living cheek by"},{"startTime":208.68,"endTime":210.9,"body":"jowl with each other."},{"startTime":210.9,"endTime":213.87,"body":"They don't talk the same way."},{"startTime":210.9,"endTime":213.87,"body":"They have different accents."},{"startTime":213.87,"endTime":216.32,"body":"You don't know these"},{"startTime":213.87,"endTime":216.32,"body":"people. They don't know you."},{"startTime":218.61,"endTime":220.92,"body":"Then couple of world wars,"},{"startTime":220.92,"endTime":224.76,"body":"and after that you have the"},{"startTime":220.92,"endTime":224.76,"body":"industrial revolution 3.0,"},{"startTime":224.76,"endTime":228.81,"body":"which started automating"},{"startTime":224.76,"endTime":228.81,"body":"back office managerial work."},{"startTime":228.81,"endTime":231.48,"body":"The first level was all operational stuff."},{"startTime":231.48,"endTime":233.31,"body":"This is managerial stuff."},{"startTime":233.31,"endTime":236.52,"body":"What happens here is that"},{"startTime":233.31,"endTime":236.52,"body":"the introduction of computers"},{"startTime":236.52,"endTime":240.48,"body":"allowed us to make the"},{"startTime":236.52,"endTime":240.48,"body":"process of manufacturing"},{"startTime":240.48,"endTime":241.313,"body":"more efficient."},{"startTime":241.313,"endTime":243.54,"body":"You're not actually changing"},{"startTime":241.313,"endTime":243.54,"body":"the manufacturing process,"},{"startTime":243.54,"endTime":246.543,"body":"you're changing the way the"},{"startTime":243.54,"endTime":246.543,"body":"back offices are organized."},{"startTime":247.89,"endTime":252.78,"body":"That created a sort of going"},{"startTime":247.89,"endTime":252.78,"body":"back to where we started out"},{"startTime":252.78,"endTime":253.77,"body":"in the beginning."},{"startTime":253.77,"endTime":256.23,"body":"Because you don't need to"},{"startTime":253.77,"endTime":256.23,"body":"be in the offices anymore,"},{"startTime":256.23,"endTime":259.68,"body":"as much as you needed"},{"startTime":256.23,"endTime":259.68,"body":"to be if you're working"},{"startTime":259.68,"endTime":261.183,"body":"on a physical assembly line."},{"startTime":262.14,"endTime":264.81,"body":"The process then became"},{"startTime":262.14,"endTime":264.81,"body":"even more complicated"},{"startTime":264.81,"endTime":266.49,"body":"when we go to today."},{"startTime":266.49,"endTime":268.98,"body":"About probably the fourth"},{"startTime":266.49,"endTime":268.98,"body":"industrial revolution,"},{"startTime":268.98,"endTime":270.99,"body":"where everything is connected,"},{"startTime":270.99,"endTime":273.33,"body":"you have networks, you have"},{"startTime":270.99,"endTime":273.33,"body":"the internet of things,"},{"startTime":273.33,"endTime":274.56,"body":"everything is literally connected."},{"startTime":274.56,"endTime":276.51,"body":"Your light bulbs are"},{"startTime":274.56,"endTime":276.51,"body":"connected to the internet."},{"startTime":276.51,"endTime":278.4,"body":"Our computers are"},{"startTime":276.51,"endTime":278.4,"body":"connected to the internet,"},{"startTime":278.4,"endTime":279.84,"body":"cameras are connected to the internet."},{"startTime":279.84,"endTime":283.29,"body":"Everything is part of a"},{"startTime":279.84,"endTime":283.29,"body":"network, and we don't need"},{"startTime":283.29,"endTime":287.7,"body":"to actually physically be in"},{"startTime":283.29,"endTime":287.7,"body":"the same space with each other."},{"startTime":287.7,"endTime":289.74,"body":"You still have a problem of trust."},{"startTime":289.74,"endTime":291.66,"body":"Now, you don't know anybody,"},{"startTime":291.66,"endTime":294.03,"body":"not because you're living next to them."},{"startTime":294.03,"endTime":295.77,"body":"It's because you never see them."},{"startTime":295.77,"endTime":298.17,"body":"How many of us, for example, in London,"},{"startTime":298.17,"endTime":299.94,"body":"know our neighbors very well?"},{"startTime":299.94,"endTime":303.21,"body":"Like many of us, we just bump"},{"startTime":299.94,"endTime":303.21,"body":"into them in the corridors"},{"startTime":303.21,"endTime":304.2,"body":"on the way in or out,"},{"startTime":304.2,"endTime":306.81,"body":"but we never don't actually"},{"startTime":304.2,"endTime":306.81,"body":"know anything about them."},{"startTime":306.81,"endTime":309.93,"body":"This is a problem with trust again."},{"startTime":309.93,"endTime":312.123,"body":"How does trust evolve in these areas?"},{"startTime":313.44,"endTime":316.71,"body":"Before 1950s, everybody's"},{"startTime":313.44,"endTime":316.71,"body":"living in small villages."},{"startTime":316.71,"endTime":318.63,"body":"It's all local trust."},{"startTime":318.63,"endTime":319.95,"body":"You know your neighbor,"},{"startTime":319.95,"endTime":322.44,"body":"you know who's the best farmer around,"},{"startTime":322.44,"endTime":325.29,"body":"you know who's the best"},{"startTime":322.44,"endTime":325.29,"body":"butcher, the best baker,"},{"startTime":325.29,"endTime":326.94,"body":"even the best candle stick maker."},{"startTime":329.19,"endTime":331.023,"body":"You deal with them on a daily basis."},{"startTime":333.06,"endTime":335.7,"body":"If they produce things"},{"startTime":333.06,"endTime":335.7,"body":"which are not up to mark,"},{"startTime":335.7,"endTime":337.35,"body":"you don't work with them anymore."},{"startTime":338.22,"endTime":341.55,"body":"Once you move to the town,"},{"startTime":338.22,"endTime":341.55,"body":"who are you dealing with?"},{"startTime":341.55,"endTime":343.89,"body":"Well, you don't know many people."},{"startTime":343.89,"endTime":346.77,"body":"You start depending on local authorities."},{"startTime":346.77,"endTime":349.74,"body":"The local magistrate,"},{"startTime":346.77,"endTime":349.74,"body":"local police officers."},{"startTime":349.74,"endTime":351.06,"body":"You may not like them,"},{"startTime":351.06,"endTime":353.58,"body":"but you certainly trust"},{"startTime":351.06,"endTime":353.58,"body":"them more than you trust"},{"startTime":353.58,"endTime":357.15,"body":"all these strangers whom you're"},{"startTime":353.58,"endTime":357.15,"body":"meeting for the first time."},{"startTime":357.15,"endTime":358.44,"body":"Once you go to the city,"},{"startTime":358.44,"endTime":360.42,"body":"that becomes even more complicated,"},{"startTime":360.42,"endTime":363.12,"body":"because the city is just too big an area"},{"startTime":363.12,"endTime":367.26,"body":"for you to be familiar with all the people"},{"startTime":367.26,"endTime":368.61,"body":"who deal with you."},{"startTime":368.61,"endTime":371.76,"body":"For example, you might deal in a town,"},{"startTime":371.76,"endTime":374.1,"body":"maybe the five or six police officers,"},{"startTime":374.1,"endTime":375.93,"body":"in a city, they're 500."},{"startTime":375.93,"endTime":377.22,"body":"You may know one person,"},{"startTime":377.22,"endTime":379.77,"body":"but there's no guarantee you"},{"startTime":377.22,"endTime":379.77,"body":"will see this person again."},{"startTime":379.77,"endTime":382.68,"body":"But you do know where"},{"startTime":379.77,"endTime":382.68,"body":"the police station is."},{"startTime":382.68,"endTime":386.01,"body":"The institution becomes more"},{"startTime":382.68,"endTime":386.01,"body":"important than the person"},{"startTime":386.01,"endTime":387.87,"body":"working for the institution."},{"startTime":387.87,"endTime":390.75,"body":"In finance, that threads to the area"},{"startTime":390.75,"endTime":393.09,"body":"of financial intermediaries."},{"startTime":393.09,"endTime":395.7,"body":"If you think about what banks were like"},{"startTime":395.7,"endTime":397.44,"body":"in that period of time,"},{"startTime":397.44,"endTime":402.09,"body":"you had illusions of"},{"startTime":397.44,"endTime":402.09,"body":"stability, massive buildings,"},{"startTime":402.09,"endTime":405.84,"body":"Big columns and statues"},{"startTime":402.09,"endTime":405.84,"body":"of important people."},{"startTime":405.84,"endTime":408.54,"body":"Banks are basically saying,"},{"startTime":405.84,"endTime":408.54,"body":"\"We are temples, almost."},{"startTime":408.54,"endTime":413.127,"body":"We walk in here, we keep your money safe.\""},{"startTime":414.39,"endTime":417.15,"body":"But as automation came"},{"startTime":414.39,"endTime":417.15,"body":"along, what would happen?"},{"startTime":417.15,"endTime":419.97,"body":"We don't actually deal that"},{"startTime":417.15,"endTime":419.97,"body":"much with our banks anymore."},{"startTime":419.97,"endTime":421.5,"body":"One bank branch is pretty similar"},{"startTime":421.5,"endTime":422.97,"body":"to any other bank branches."},{"startTime":422.97,"endTime":425.91,"body":"There's nothing special"},{"startTime":422.97,"endTime":425.91,"body":"about a bank branch."},{"startTime":425.91,"endTime":429.33,"body":"Now, you trust the system."},{"startTime":425.91,"endTime":429.33,"body":"What is the system?"},{"startTime":429.33,"endTime":431.85,"body":"Well, if a bank collapses, that's fine,"},{"startTime":431.85,"endTime":436.2,"body":"because the government will"},{"startTime":431.85,"endTime":436.2,"body":"bail you out like this."},{"startTime":436.2,"endTime":438.27,"body":"The system becomes more important"},{"startTime":438.27,"endTime":441.0,"body":"than the individual people"},{"startTime":438.27,"endTime":441.0,"body":"involved in the system."},{"startTime":441.0,"endTime":443.04,"body":"It's slowly moving from a system"},{"startTime":443.04,"endTime":446.58,"body":"where you have human"},{"startTime":443.04,"endTime":446.58,"body":"beings to intermediaries,"},{"startTime":446.58,"endTime":448.74,"body":"where human beings are still"},{"startTime":446.58,"endTime":448.74,"body":"working for the intermediaries"},{"startTime":448.74,"endTime":451.62,"body":"to a system governing the intermediaries."},{"startTime":451.62,"endTime":453.66,"body":"What about today?"},{"startTime":453.66,"endTime":455.58,"body":"Well, going back to one of the slides"},{"startTime":455.58,"endTime":457.323,"body":"which I showed in my last lecture."},{"startTime":459.9,"endTime":461.79,"body":"If you look at the intermediaries today,"},{"startTime":461.79,"endTime":463.62,"body":"and you look at the system,"},{"startTime":463.62,"endTime":467.97,"body":"this is a survey carried out"},{"startTime":463.62,"endTime":467.97,"body":"by the Edelman Trust barometer."},{"startTime":467.97,"endTime":470.197,"body":"Every year they ask people,"},{"startTime":470.197,"endTime":473.31,"body":"\"How much do you trust"},{"startTime":470.197,"endTime":473.31,"body":"businesses in these industries"},{"startTime":473.31,"endTime":474.96,"body":"to do the right thing?\""},{"startTime":474.96,"endTime":476.88,"body":"They don't really define the right thing,"},{"startTime":476.88,"endTime":478.95,"body":"but the right thing."},{"startTime":478.95,"endTime":482.04,"body":"Banks are almost"},{"startTime":478.95,"endTime":482.04,"body":"consistently at the bottom"},{"startTime":482.04,"endTime":485.49,"body":"of the league tables, and"},{"startTime":482.04,"endTime":485.49,"body":"that's not surprising."},{"startTime":485.49,"endTime":487.56,"body":"Banks offer complex products"},{"startTime":487.56,"endTime":489.27,"body":"which are difficult to understand,"},{"startTime":489.27,"endTime":491.28,"body":"and then you get the impression"},{"startTime":491.28,"endTime":493.833,"body":"the banks like nothing"},{"startTime":491.28,"endTime":493.833,"body":"better than to rip you off."},{"startTime":495.09,"endTime":498.03,"body":"For example, healthcare offers"},{"startTime":495.09,"endTime":498.03,"body":"equally complex products,"},{"startTime":498.03,"endTime":499.68,"body":"equally difficult to understand,"},{"startTime":499.68,"endTime":501.6,"body":"but at least you think you and they"},{"startTime":501.6,"endTime":504.15,"body":"have the common interest"},{"startTime":501.6,"endTime":504.15,"body":"of saving your life."},{"startTime":504.15,"endTime":506.55,"body":"Not necessarily so for a bank."},{"startTime":506.55,"endTime":508.5,"body":"Banks are consistently at the bottom."},{"startTime":508.5,"endTime":509.91,"body":"We don't trust the banks,"},{"startTime":509.91,"endTime":512.01,"body":"we don't trust the financial systems."},{"startTime":512.01,"endTime":515.583,"body":"So what can replace these institutions?"},{"startTime":517.11,"endTime":520.29,"body":"I'm going to argue that"},{"startTime":517.11,"endTime":520.29,"body":"there's today's world,"},{"startTime":520.29,"endTime":522.72,"body":"we are thinking about"},{"startTime":520.29,"endTime":522.72,"body":"technology to replace"},{"startTime":522.72,"endTime":526.71,"body":"that level of trust, and"},{"startTime":522.72,"endTime":526.71,"body":"that's the area of crypto."},{"startTime":526.71,"endTime":528.633,"body":"But what do we know about crypto?"},{"startTime":530.01,"endTime":532.71,"body":"Well, one thing we know"},{"startTime":530.01,"endTime":532.71,"body":"is that there's a ton"},{"startTime":532.71,"endTime":534.033,"body":"of complicated jargon."},{"startTime":534.93,"endTime":537.03,"body":"We talk about distributed"},{"startTime":534.93,"endTime":537.03,"body":"ledger technology,"},{"startTime":537.03,"endTime":540.06,"body":"talk about blockchains, consensus"},{"startTime":537.03,"endTime":540.06,"body":"protocol, smart contract,"},{"startTime":540.06,"endTime":541.65,"body":"shared databases."},{"startTime":541.65,"endTime":544.053,"body":"Basically, it's a bunch"},{"startTime":541.65,"endTime":544.053,"body":"of blah, blah, blah."},{"startTime":545.01,"endTime":547.38,"body":"I can tell you honestly"},{"startTime":545.01,"endTime":547.38,"body":"that if your partner"},{"startTime":547.38,"endTime":548.85,"body":"has trouble sleeping at night,"},{"startTime":548.85,"endTime":551.04,"body":"just discuss a blockchain protocol,"},{"startTime":551.04,"endTime":552.633,"body":"they go to sleep right away."},{"startTime":554.1,"endTime":557.01,"body":"The consensus is if you"},{"startTime":554.1,"endTime":557.01,"body":"have some kind of technology"},{"startTime":557.01,"endTime":560.373,"body":"like this, it's very difficult"},{"startTime":557.01,"endTime":560.373,"body":"to understand how it works,"},{"startTime":561.21,"endTime":564.753,"body":"and it's very difficult to"},{"startTime":561.21,"endTime":564.753,"body":"understand why it is important."},{"startTime":567.03,"endTime":568.29,"body":"At this stage,"},{"startTime":568.29,"endTime":572.403,"body":"I want to make a distinction"},{"startTime":568.29,"endTime":572.403,"body":"between blockchain and crypto."},{"startTime":573.87,"endTime":577.08,"body":"Crypto is a general phrase that arises"},{"startTime":577.08,"endTime":579.0,"body":"to apply to a lot of transactions."},{"startTime":579.0,"endTime":581.37,"body":"For example, if we talk about currency,"},{"startTime":581.37,"endTime":582.84,"body":"we talk about cryptocurrencies,"},{"startTime":582.84,"endTime":585.21,"body":"which is replacement for money."},{"startTime":585.21,"endTime":587.31,"body":"We can talk about contracts."},{"startTime":587.31,"endTime":590.16,"body":"We can talk about smart"},{"startTime":587.31,"endTime":590.16,"body":"contracts, decentralized finance,"},{"startTime":590.16,"endTime":591.75,"body":"things like that."},{"startTime":591.75,"endTime":594.36,"body":"These are topics I will not cover today."},{"startTime":594.36,"endTime":595.77,"body":"These are topics which I reserved"},{"startTime":595.77,"endTime":598.23,"body":"for my third lecture in January."},{"startTime":598.23,"endTime":602.2,"body":"I talk about the applications"},{"startTime":598.23,"endTime":602.2,"body":"of this technology"},{"startTime":603.33,"endTime":605.76,"body":"to these kind of transactions."},{"startTime":605.76,"endTime":607.24,"body":"Today I'm actually going to talk"},{"startTime":607.24,"endTime":609.72,"body":"about the underlying"},{"startTime":607.24,"endTime":609.72,"body":"technology, the blockchain."},{"startTime":609.72,"endTime":612.03,"body":"How does the blockchain work?"},{"startTime":612.03,"endTime":613.893,"body":"Let's start with a big picture."},{"startTime":616.56,"endTime":619.5,"body":"Well, there are three major things"},{"startTime":619.5,"endTime":621.78,"body":"which blockchains allow us to do."},{"startTime":621.78,"endTime":624.603,"body":"One is users want to be anonymous."},{"startTime":625.98,"endTime":628.713,"body":"We are using cryptography"},{"startTime":625.98,"endTime":628.713,"body":"to protect anonymity."},{"startTime":629.82,"endTime":632.7,"body":"Second, the data is"},{"startTime":629.82,"endTime":632.7,"body":"completely unstructured."},{"startTime":632.7,"endTime":635.55,"body":"That means anything can"},{"startTime":632.7,"endTime":635.55,"body":"be put into a blockchain,"},{"startTime":635.55,"endTime":640.55,"body":"ranging from one line, one"},{"startTime":635.55,"endTime":640.55,"body":"sentence to an entire novel."},{"startTime":640.83,"endTime":643.863,"body":"Anything can be put into"},{"startTime":640.83,"endTime":643.863,"body":"the same blockchain."},{"startTime":644.79,"endTime":648.51,"body":"Third, the data is indelible."},{"startTime":648.51,"endTime":650.49,"body":"That means no one can alter the data"},{"startTime":650.49,"endTime":652.037,"body":"without everybody finding out."},{"startTime":652.037,"endTime":654.48,"body":"We are going to use something"},{"startTime":652.037,"endTime":654.48,"body":"called proof of work,"},{"startTime":654.48,"endTime":656.883,"body":"or proof of stake to validate the data."},{"startTime":658.41,"endTime":660.277,"body":"I can see what some of you are thinking,"},{"startTime":660.277,"endTime":663.0,"body":"\"Man, the guy said he's not"},{"startTime":660.277,"endTime":663.0,"body":"going to use any jargon,"},{"startTime":663.0,"endTime":664.62,"body":"is already using jargon.\""},{"startTime":664.62,"endTime":667.11,"body":"What's the rest of the"},{"startTime":664.62,"endTime":667.11,"body":"lecture going to be like?"},{"startTime":667.11,"endTime":671.07,"body":"Well, let me go back a little bit."},{"startTime":671.07,"endTime":674.73,"body":"Let's start with a very"},{"startTime":671.07,"endTime":674.73,"body":"simple idea: a bank ledger."},{"startTime":674.73,"endTime":676.293,"body":"How does a bank ledger work?"},{"startTime":677.28,"endTime":680.52,"body":"Let's say you are going to"},{"startTime":677.28,"endTime":680.52,"body":"pay some money to your friend,"},{"startTime":680.52,"endTime":683.52,"body":"in the same bank as you"},{"startTime":680.52,"endTime":683.52,"body":"for simplicity's sake."},{"startTime":683.52,"endTime":685.863,"body":"How does the bank record this transaction?"},{"startTime":686.76,"endTime":690.33,"body":"Well, what happens is the"},{"startTime":686.76,"endTime":690.33,"body":"bank makes a ledger entry"},{"startTime":690.33,"endTime":693.87,"body":"and each ledger entry"},{"startTime":690.33,"endTime":693.87,"body":"contain some information."},{"startTime":693.87,"endTime":696.51,"body":"For example, it has the originating person"},{"startTime":696.51,"endTime":697.95,"body":"plus their account number,"},{"startTime":697.95,"endTime":700.53,"body":"the destination person"},{"startTime":697.95,"endTime":700.53,"body":"plus their account number"},{"startTime":700.53,"endTime":702.06,"body":"and the transaction detail."},{"startTime":702.06,"endTime":704.013,"body":"How much money is being transferred."},{"startTime":705.21,"endTime":707.37,"body":"The bank then takes that ledge entry"},{"startTime":707.37,"endTime":709.83,"body":"and applies it to your accounts."},{"startTime":709.83,"endTime":712.23,"body":"The account entry will"},{"startTime":709.83,"endTime":712.23,"body":"have your starting balance."},{"startTime":712.23,"endTime":713.49,"body":"How much is being transferred?"},{"startTime":713.49,"endTime":714.49,"body":"Your ending balance."},{"startTime":715.47,"endTime":718.86,"body":"To take an example, this"},{"startTime":715.47,"endTime":718.86,"body":"is what it might look like."},{"startTime":718.86,"endTime":722.13,"body":"Let's suppose that Mr."},{"startTime":718.86,"endTime":722.13,"body":"Black writes a check"},{"startTime":722.13,"endTime":726.0,"body":"to transfer five Bitcoin from"},{"startTime":722.13,"endTime":726.0,"body":"his account to Ms. Green."},{"startTime":726.0,"endTime":728.52,"body":"I'm aware of the irony"},{"startTime":726.0,"endTime":728.52,"body":"that you're writing a check"},{"startTime":728.52,"endTime":730.98,"body":"to transfer Bitcoin,"},{"startTime":730.98,"endTime":735.3,"body":"but for simplicity's sake,"},{"startTime":730.98,"endTime":735.3,"body":"just go as basic as possible."},{"startTime":735.3,"endTime":737.647,"body":"It is entirely possible to"},{"startTime":735.3,"endTime":737.647,"body":"write a check with, say,"},{"startTime":737.647,"endTime":739.56,"body":"\"Transfer Bitcoin from my wallet"},{"startTime":739.56,"endTime":740.94,"body":"to the other person's wallet,"},{"startTime":740.94,"endTime":742.65,"body":"as long as the bank holds a private key.\""},{"startTime":742.65,"endTime":743.97,"body":"We leave that for a minute,"},{"startTime":743.97,"endTime":746.733,"body":"but we are assuming this"},{"startTime":743.97,"endTime":746.733,"body":"is a simple transaction."},{"startTime":748.56,"endTime":750.78,"body":"Mr. Black here is the originator."},{"startTime":750.78,"endTime":752.64,"body":"Ms. Green is the destination."},{"startTime":752.64,"endTime":755.34,"body":"The ledger entry looks like this."},{"startTime":755.34,"endTime":756.997,"body":"Very simple ledger entry."},{"startTime":756.997,"endTime":760.29,"body":"\"Five bitcoin transferred"},{"startTime":756.997,"endTime":760.29,"body":"from Mr. Black to Ms. Green.\""},{"startTime":760.29,"endTime":761.89,"body":"What does the account look like?"},{"startTime":762.75,"endTime":764.67,"body":"It looks like that's the date,"},{"startTime":764.67,"endTime":766.56,"body":"starting balance from Mr. Black."},{"startTime":766.56,"endTime":767.94,"body":"That's the amount debited."},{"startTime":767.94,"endTime":769.71,"body":"Five Bitcoin is the ending balance."},{"startTime":769.71,"endTime":771.753,"body":"Very simple, very straightforward."},{"startTime":772.71,"endTime":775.953,"body":"Now, what are the problems that"},{"startTime":772.71,"endTime":775.953,"body":"might arise in this system?"},{"startTime":777.39,"endTime":780.87,"body":"The first problem is"},{"startTime":777.39,"endTime":780.87,"body":"maybe the bank manager"},{"startTime":780.87,"endTime":785.87,"body":"who keeps the records diverts"},{"startTime":780.87,"endTime":785.87,"body":"the money to her own account."},{"startTime":785.91,"endTime":789.39,"body":"Basically, she falsifies the transaction."},{"startTime":789.39,"endTime":791.04,"body":"What does that mean?"},{"startTime":791.04,"endTime":792.81,"body":"Instead of writing, \"Ms. Green,\""},{"startTime":792.81,"endTime":795.0,"body":"she writes her own name"},{"startTime":792.81,"endTime":795.0,"body":"and transfer the money"},{"startTime":795.0,"endTime":795.95,"body":"to her own account."},{"startTime":797.1,"endTime":801.65,"body":"Second possibility, maybe Mr."},{"startTime":797.1,"endTime":801.65,"body":"Black doesn't have any money"},{"startTime":801.65,"endTime":803.37,"body":"in his own account in the first place."},{"startTime":803.37,"endTime":805.743,"body":"So when you write a"},{"startTime":803.37,"endTime":805.743,"body":"check, the check bounces."},{"startTime":807.24,"endTime":808.44,"body":"Third possibility."},{"startTime":808.44,"endTime":810.6,"body":"Maybe I give my money to Ms. Green,"},{"startTime":810.6,"endTime":812.67,"body":"she takes a check from me,"},{"startTime":812.67,"endTime":815.37,"body":"but before she has a chance"},{"startTime":812.67,"endTime":815.37,"body":"to deposit the check,"},{"startTime":815.37,"endTime":818.4,"body":"I go and spend the"},{"startTime":815.37,"endTime":818.4,"body":"money on something else."},{"startTime":818.4,"endTime":820.713,"body":"Maybe to buy a coffee."},{"startTime":818.4,"endTime":820.713,"body":"I'm double spending."},{"startTime":821.7,"endTime":825.78,"body":"Or maybe I don't want"},{"startTime":821.7,"endTime":825.78,"body":"anyone, even my bank manager,"},{"startTime":825.78,"endTime":828.36,"body":"to know that I need to"},{"startTime":825.78,"endTime":828.36,"body":"send funds from Ms. Green."},{"startTime":828.36,"endTime":830.13,"body":"That means I want to be anonymous."},{"startTime":830.13,"endTime":831.75,"body":"These are the problems I need."},{"startTime":831.75,"endTime":834.63,"body":"I need to solve the"},{"startTime":831.75,"endTime":834.63,"body":"problem of falsification."},{"startTime":834.63,"endTime":836.79,"body":"I need to solve the"},{"startTime":834.63,"endTime":836.79,"body":"problem of double spending."},{"startTime":836.79,"endTime":838.89,"body":"I need to solve the problem of anonymity."},{"startTime":838.89,"endTime":841.14,"body":"These are the issues"},{"startTime":838.89,"endTime":841.14,"body":"which I'm trying to solve"},{"startTime":841.14,"endTime":842.85,"body":"using technology."},{"startTime":842.85,"endTime":844.4,"body":"So, how does a blockchain help?"},{"startTime":845.64,"endTime":847.323,"body":"No one has control of the ledger."},{"startTime":848.67,"endTime":849.57,"body":"In other words,"},{"startTime":849.57,"endTime":852.03,"body":"Ms. Red cannot divert the"},{"startTime":849.57,"endTime":852.03,"body":"money to her own account."},{"startTime":852.03,"endTime":855.0,"body":"In general, no one can"},{"startTime":852.03,"endTime":855.0,"body":"falsify anything on the chain,"},{"startTime":855.0,"endTime":857.583,"body":"even though nobody is"},{"startTime":855.0,"endTime":857.583,"body":"responsible for the ledger."},{"startTime":858.51,"endTime":859.95,"body":"There should be no way for Mr. Black"},{"startTime":859.95,"endTime":861.66,"body":"to spend the same money twice."},{"startTime":861.66,"endTime":864.36,"body":"And best of all, everybody's"},{"startTime":861.66,"endTime":864.36,"body":"identity can be kept"},{"startTime":864.36,"endTime":866.043,"body":"completely secret."},{"startTime":868.74,"endTime":869.91,"body":"The key points."},{"startTime":869.91,"endTime":872.7,"body":"There's some key points"},{"startTime":869.91,"endTime":872.7,"body":"which I need to make."},{"startTime":872.7,"endTime":875.61,"body":"The important thing to"},{"startTime":872.7,"endTime":875.61,"body":"realize is a blockchain"},{"startTime":875.61,"endTime":879.27,"body":"is a way to store data"},{"startTime":875.61,"endTime":879.27,"body":"when you do not trust"},{"startTime":879.27,"endTime":880.323,"body":"your counterparty."},{"startTime":882.15,"endTime":884.34,"body":"Trust is ensured by technology."},{"startTime":884.34,"endTime":887.88,"body":"What this means is, if you"},{"startTime":884.34,"endTime":887.88,"body":"trust your counterparty,"},{"startTime":887.88,"endTime":889.28,"body":"you don't need a blockchain."},{"startTime":890.67,"endTime":892.23,"body":"If you do not need to store data,"},{"startTime":892.23,"endTime":894.54,"body":"you do not need a blockchain."},{"startTime":894.54,"endTime":895.41,"body":"You need both."},{"startTime":895.41,"endTime":896.82,"body":"If you don't trust your counterparty"},{"startTime":896.82,"endTime":898.86,"body":"and you don't need to store data,"},{"startTime":898.86,"endTime":900.69,"body":"blockchain is not really relevant."},{"startTime":900.69,"endTime":903.213,"body":"It's a method of storing data."},{"startTime":905.37,"endTime":907.77,"body":"So, what are the different"},{"startTime":905.37,"endTime":907.77,"body":"types of blockchains?"},{"startTime":907.77,"endTime":910.07,"body":"Turns out there are four"},{"startTime":907.77,"endTime":910.07,"body":"types of blockchains."},{"startTime":910.98,"endTime":912.66,"body":"If everybody's allowed to read entries,"},{"startTime":912.66,"endTime":914.49,"body":"it's called a public blockchain."},{"startTime":914.49,"endTime":917.43,"body":"Otherwise, it's called"},{"startTime":914.49,"endTime":917.43,"body":"a private blockchain."},{"startTime":917.43,"endTime":919.17,"body":"If everyone is allowed to write entries,"},{"startTime":919.17,"endTime":921.21,"body":"it's called a permissionless blockchain."},{"startTime":921.21,"endTime":924.36,"body":"That means you need permission"},{"startTime":921.21,"endTime":924.36,"body":"to write in the blockchain."},{"startTime":924.36,"endTime":926.07,"body":"Otherwise, it's a permissioned blockchain."},{"startTime":926.07,"endTime":928.92,"body":"You need permission to"},{"startTime":926.07,"endTime":928.92,"body":"write in the blockchain."},{"startTime":928.92,"endTime":930.87,"body":"Basically, you have these four types."},{"startTime":930.87,"endTime":933.51,"body":"Anyone can read, anyone can write."},{"startTime":933.51,"endTime":934.617,"body":"That's public permissionless."},{"startTime":934.617,"endTime":936.9,"body":"You have four combinations."},{"startTime":936.9,"endTime":938.61,"body":"You can see these combinations"},{"startTime":938.61,"endTime":940.47,"body":"when you have a complete picture,"},{"startTime":940.47,"endTime":941.94,"body":"which sort of looks like this."},{"startTime":941.94,"endTime":945.36,"body":"If you're trusted, there's"},{"startTime":941.94,"endTime":945.36,"body":"no need for a blockchain."},{"startTime":945.36,"endTime":947.88,"body":"If you are untrusted counterparties,"},{"startTime":947.88,"endTime":950.22,"body":"but you have a limited"},{"startTime":947.88,"endTime":950.22,"body":"number of counterparties,"},{"startTime":950.22,"endTime":951.6,"body":"you have a permissioned blockchain"},{"startTime":951.6,"endTime":954.0,"body":"that only a few people can read or write."},{"startTime":954.0,"endTime":957.24,"body":"But you need to let maybe the"},{"startTime":954.0,"endTime":957.24,"body":"government tax authorities"},{"startTime":957.24,"endTime":959.64,"body":"to check those transactions later on,"},{"startTime":959.64,"endTime":962.55,"body":"or an audit committee to"},{"startTime":959.64,"endTime":962.55,"body":"check the numbers later on."},{"startTime":962.55,"endTime":965.28,"body":"You need a public, anyone can read it,"},{"startTime":965.28,"endTime":967.35,"body":"permissioned, only a few people can write,"},{"startTime":967.35,"endTime":970.17,"body":"a public permissioned blockchain."},{"startTime":970.17,"endTime":972.12,"body":"If you don't need to let"},{"startTime":970.17,"endTime":972.12,"body":"outsiders look at the data,"},{"startTime":972.12,"endTime":973.71,"body":"you can have everything private."},{"startTime":973.71,"endTime":977.01,"body":"Private permissioned blockchain,"},{"startTime":973.71,"endTime":977.01,"body":"only a few people can read."},{"startTime":977.01,"endTime":978.72,"body":"Only a few people can write."},{"startTime":978.72,"endTime":980.19,"body":"But the most general form,"},{"startTime":980.19,"endTime":982.17,"body":"the part which we're"},{"startTime":980.19,"endTime":982.17,"body":"going to talk about today"},{"startTime":982.17,"endTime":984.6,"body":"is a public permissionless blockchain."},{"startTime":984.6,"endTime":987.34,"body":"A classic example of that is Bitcoin."},{"startTime":990.51,"endTime":991.81,"body":"The bottom line is simple."},{"startTime":993.15,"endTime":995.643,"body":"Blockchains need to solve three problems."},{"startTime":996.51,"endTime":999.33,"body":"Problem number one, no falsification."},{"startTime":999.33,"endTime":1001.94,"body":"Problem number two, no double spending."},{"startTime":1001.94,"endTime":1003.863,"body":"Problem number three, anonymity."},{"speaker":"And they do this using three technologies","startTime":1007.67,"endTime":1010.043,"body":"cryptography, hashing, and mining."},{"speaker":"And they do this using three technologies","startTime":1012.2,"endTime":1013.763,"body":"How did this come about?"},{"speaker":"And they do this using three technologies","startTime":1015.316,"endTime":1018.143,"body":"How were blockchains created?"},{"speaker":"And they do this using three technologies","startTime":1019.43,"endTime":1021.62,"body":"Let me go back to 2008."},{"speaker":"And they do this using three technologies","startTime":1021.62,"endTime":1024.29,"body":"In fact, Halloween, 2008;"},{"speaker":"And they do this using three technologies","startTime":1024.29,"endTime":1027.77,"body":"that's when this person"},{"speaker":"And they do this using three technologies","startTime":1024.29,"endTime":1027.77,"body":"called Satoshi Nakamoto"},{"speaker":"And they do this using three technologies","startTime":1027.77,"endTime":1031.49,"body":"wrote a white paper"},{"speaker":"And they do this using three technologies","startTime":1027.77,"endTime":1031.49,"body":"talking about the emergency"},{"speaker":"And they do this using three technologies","startTime":1031.49,"endTime":1033.953,"body":"of peer-to-peer system"},{"speaker":"And they do this using three technologies","startTime":1031.49,"endTime":1033.953,"body":"for transferring money."},{"speaker":"And they do this using three technologies","startTime":1034.91,"endTime":1037.31,"body":"Now, what is interesting"},{"speaker":"And they do this using three technologies","startTime":1034.91,"endTime":1037.31,"body":"about this is number one:"},{"speaker":"And they do this using three technologies","startTime":1037.31,"endTime":1040.37,"body":"nobody knows who Satoshi Nakamoto is."},{"speaker":"And they do this using three technologies","startTime":1040.37,"endTime":1041.72,"body":"Could be a man, could be a woman,"},{"speaker":"And they do this using three technologies","startTime":1041.72,"endTime":1042.86,"body":"could be a group of people."},{"speaker":"And they do this using three technologies","startTime":1042.86,"endTime":1046.31,"body":"We have no idea. It's"},{"speaker":"And they do this using three technologies","startTime":1042.86,"endTime":1046.31,"body":"completely anonymous."},{"speaker":"And they do this using three technologies","startTime":1046.31,"endTime":1050.0,"body":"Second thing is that nobody"},{"speaker":"And they do this using three technologies","startTime":1046.31,"endTime":1050.0,"body":"knew how to price this."},{"speaker":"And they do this using three technologies","startTime":1050.0,"endTime":1051.47,"body":"It wasn't original."},{"speaker":"And they do this using three technologies","startTime":1051.47,"endTime":1054.05,"body":"There are a whole bunch"},{"speaker":"And they do this using three technologies","startTime":1051.47,"endTime":1054.05,"body":"of other electronic money"},{"speaker":"And they do this using three technologies","startTime":1054.05,"endTime":1054.883,"body":"before this."},{"speaker":"And they do this using three technologies","startTime":1054.883,"endTime":1058.64,"body":"For example, Digi Cash was"},{"speaker":"And they do this using three technologies","startTime":1054.883,"endTime":1058.64,"body":"being used in the 1990s."},{"speaker":"And they do this using three technologies","startTime":1058.64,"endTime":1060.2,"body":"It's a form of electronic money."},{"speaker":"And they do this using three technologies","startTime":1060.2,"endTime":1065.09,"body":"Never really caught on, but Bitcoin did."},{"speaker":"And they do this using three technologies","startTime":1065.09,"endTime":1068.42,"body":"What made Bitcoin take off?"},{"speaker":"And they do this using three technologies","startTime":1068.42,"endTime":1072.7,"body":"Well, first thing is Bitcoin"},{"speaker":"And they do this using three technologies","startTime":1068.42,"endTime":1072.7,"body":"being priced at that time."},{"speaker":"And they do this using three technologies","startTime":1072.7,"endTime":1076.04,"body":"In 2009, one of Nakamoto's colleagues,"},{"speaker":"And they do this using three technologies","startTime":1076.04,"endTime":1077.57,"body":"the way he priced it was simple."},{"speaker":"And they do this using three technologies","startTime":1077.57,"endTime":1081.2,"body":"He spent a month mining"},{"speaker":"And they do this using three technologies","startTime":1077.57,"endTime":1081.2,"body":"Bitcoin on his laptop."},{"speaker":"And they do this using three technologies","startTime":1081.2,"endTime":1083.3,"body":"He looked at his electricity"},{"speaker":"And they do this using three technologies","startTime":1081.2,"endTime":1083.3,"body":"bill the previous month,"},{"speaker":"And they do this using three technologies","startTime":1083.3,"endTime":1085.25,"body":"he looked at his electricity"},{"speaker":"And they do this using three technologies","startTime":1083.3,"endTime":1085.25,"body":"bill the next month,"},{"speaker":"And they do this using three technologies","startTime":1085.25,"endTime":1088.46,"body":"all he had done was mine"},{"speaker":"And they do this using three technologies","startTime":1085.25,"endTime":1088.46,"body":"Bitcoin during that month."},{"speaker":"And they do this using three technologies","startTime":1088.46,"endTime":1092.9,"body":"He said, \"I have spent $20 on electricity."},{"speaker":"And they do this using three technologies","startTime":1092.9,"endTime":1095.267,"body":"This is the number of"},{"speaker":"And they do this using three technologies","startTime":1092.9,"endTime":1095.267,"body":"Bitcoins I have mined.\""},{"speaker":"And they do this using three technologies","startTime":1096.65,"endTime":1101.65,"body":"The price of a Bitcoin was"},{"speaker":"And they do this using three technologies","startTime":1096.65,"endTime":1101.65,"body":"1,980 Bitcoin per dollar."},{"speaker":"And they do this using three technologies","startTime":1104.36,"endTime":1108.98,"body":"If you could go back to 2008"},{"speaker":"And they do this using three technologies","startTime":1104.36,"endTime":1108.98,"body":"and buy $1 worth of Bitcoin,"},{"speaker":"And they do this using three technologies","startTime":1108.98,"endTime":1112.91,"body":"at its height in the beginning of 2022,"},{"speaker":"And they do this using three technologies","startTime":1112.91,"endTime":1115.643,"body":"that would have been worth $12 billion."},{"speaker":"And they do this using three technologies","startTime":1117.14,"endTime":1119.282,"body":"This is the time when I really say,"},{"speaker":"And they do this using three technologies","startTime":1119.282,"endTime":1121.782,"body":"\"Damn it, I wish someone"},{"speaker":"And they do this using three technologies","startTime":1119.282,"endTime":1121.782,"body":"invented a time machine.\""},{"speaker":"And they do this using three technologies","startTime":1122.78,"endTime":1127.78,"body":"But anyway, Bitcoin bopped"},{"speaker":"And they do this using three technologies","startTime":1122.78,"endTime":1127.78,"body":"along for a few more years."},{"speaker":"And they do this using three technologies","startTime":1128.75,"endTime":1130.73,"body":"Nobody really was using it."},{"speaker":"And they do this using three technologies","startTime":1130.73,"endTime":1135.73,"body":"A few people were using"},{"speaker":"And they do this using three technologies","startTime":1130.73,"endTime":1135.73,"body":"Bitcoin to buy pizzas,"},{"speaker":"And they do this using three technologies","startTime":1136.25,"endTime":1137.083,"body":"things like that."},{"speaker":"And they do this using three technologies","startTime":1137.083,"endTime":1138.71,"body":"It wasn't really that big a deal."},{"speaker":"And they do this using three technologies","startTime":1139.61,"endTime":1143.483,"body":"But then in 2013, something"},{"speaker":"And they do this using three technologies","startTime":1139.61,"endTime":1143.483,"body":"else happened. WikiLeaks."},{"speaker":"And they do this using three technologies","startTime":1144.77,"endTime":1147.17,"body":"WikiLeaks basically, if you remember,"},{"speaker":"And they do this using three technologies","startTime":1147.17,"endTime":1152.17,"body":"was when this website basically"},{"speaker":"And they do this using three technologies","startTime":1147.17,"endTime":1152.17,"body":"gave away all the secrets"},{"speaker":"And they do this using three technologies","startTime":1152.27,"endTime":1154.13,"body":"which the American government was holding,"},{"speaker":"And they do this using three technologies","startTime":1154.13,"endTime":1156.41,"body":"and just published it on their website."},{"speaker":"And they do this using three technologies","startTime":1156.41,"endTime":1158.27,"body":"American government was not happy,"},{"speaker":"And they do this using three technologies","startTime":1158.27,"endTime":1159.68,"body":"declared these guys as terrorists,"},{"speaker":"And they do this using three technologies","startTime":1159.68,"endTime":1162.71,"body":"and banned them from using"},{"speaker":"And they do this using three technologies","startTime":1159.68,"endTime":1162.71,"body":"the US financial system."},{"speaker":"And they do this using three technologies","startTime":1162.71,"endTime":1166.49,"body":"These guys said, \"Fine,"},{"speaker":"And they do this using three technologies","startTime":1162.71,"endTime":1166.49,"body":"we'll use Bitcoin.\""},{"speaker":"And they do this using three technologies","startTime":1166.49,"endTime":1167.84,"body":"Now, the whole point, of course,"},{"speaker":"And they do this using three technologies","startTime":1167.84,"endTime":1169.67,"body":"is the people who created Bitcoin"},{"speaker":"And they do this using three technologies","startTime":1169.67,"endTime":1173.06,"body":"didn't necessarily want"},{"speaker":"And they do this using three technologies","startTime":1169.67,"endTime":1173.06,"body":"these people using Bitcoin,"},{"speaker":"And they do this using three technologies","startTime":1173.06,"endTime":1174.29,"body":"but they had no choice."},{"speaker":"And they do this using three technologies","startTime":1174.29,"endTime":1177.23,"body":"Decentralized system. Anyone can use it."},{"speaker":"And they do this using three technologies","startTime":1177.23,"endTime":1180.034,"body":"You can't stop anyone from using it."},{"speaker":"And they do this using three technologies","startTime":1180.034,"endTime":1182.63,"body":"WikiLeaks started accepting Bitcoin."},{"speaker":"And they do this using three technologies","startTime":1182.63,"endTime":1185.12,"body":"The price of Bitcoin started increasing."},{"speaker":"And they do this using three technologies","startTime":1185.12,"endTime":1189.53,"body":"Apparently, Nakamoto"},{"speaker":"And they do this using three technologies","startTime":1185.12,"endTime":1189.53,"body":"was still collaborating"},{"speaker":"And they do this using three technologies","startTime":1189.53,"endTime":1191.42,"body":"with a whole bunch of"},{"speaker":"And they do this using three technologies","startTime":1189.53,"endTime":1191.42,"body":"people on discussion boards"},{"speaker":"And they do this using three technologies","startTime":1191.42,"endTime":1192.29,"body":"in that time."},{"speaker":"And they do this using three technologies","startTime":1192.29,"endTime":1194.42,"body":"Identity was so secret."},{"speaker":"And they do this using three technologies","startTime":1194.42,"endTime":1198.027,"body":"But then somebody said to Nakamoto,"},{"speaker":"And they do this using three technologies","startTime":1198.027,"endTime":1200.57,"body":"\"Look, the FBI is coming"},{"speaker":"And they do this using three technologies","startTime":1198.027,"endTime":1200.57,"body":"to talk to me tomorrow"},{"speaker":"And they do this using three technologies","startTime":1200.57,"endTime":1201.66,"body":"about Bitcoin."},{"speaker":"And they do this using three technologies","startTime":1203.72,"endTime":1205.4,"body":"What do you think I should tell them?\""},{"speaker":"And they do this using three technologies","startTime":1205.4,"endTime":1206.87,"body":"Nakamoto, apparently the next day,"},{"speaker":"And they do this using three technologies","startTime":1206.87,"endTime":1207.897,"body":"sent out a message saying,"},{"speaker":"And they do this using three technologies","startTime":1207.897,"endTime":1212.75,"body":"\"I'm glad to see Bitcoin is in"},{"speaker":"And they do this using three technologies","startTime":1207.897,"endTime":1212.75,"body":"good hands,\" and disappeared."},{"speaker":"And they do this using three technologies","startTime":1212.75,"endTime":1214.28,"body":"So no one knows who he is."},{"speaker":"And they do this using three technologies","startTime":1214.28,"endTime":1216.44,"body":"No one's ever found out who Nakamoto is."},{"speaker":"And they do this using three technologies","startTime":1216.44,"endTime":1220.82,"body":"And basically, as I'll"},{"speaker":"And they do this using three technologies","startTime":1216.44,"endTime":1220.82,"body":"tell you in a little bit,"},{"speaker":"And they do this using three technologies","startTime":1220.82,"endTime":1222.89,"body":"no one can prove they're Nakamoto either."},{"speaker":"And they do this using three technologies","startTime":1222.89,"endTime":1226.25,"body":"Several people have tried"},{"speaker":"And they do this using three technologies","startTime":1222.89,"endTime":1226.25,"body":"claiming they're Nakamoto."},{"speaker":"And they do this using three technologies","startTime":1226.25,"endTime":1229.523,"body":"But anyway, that's the"},{"speaker":"And they do this using three technologies","startTime":1226.25,"endTime":1229.523,"body":"origin story of Bitcoin."},{"speaker":"And they do this using three technologies","startTime":1229.523,"endTime":1234.44,"body":"It's a currency that actually"},{"speaker":"And they do this using three technologies","startTime":1229.523,"endTime":1234.44,"body":"became well used and famous,"},{"speaker":"And they do this using three technologies","startTime":1234.44,"endTime":1237.74,"body":"mainly because of an external event"},{"speaker":"And they do this using three technologies","startTime":1237.74,"endTime":1239.423,"body":"which they had no control over."},{"speaker":"And they do this using three technologies","startTime":1240.56,"endTime":1242.993,"body":"In a way it was serendipitous."},{"speaker":"And they do this using three technologies","startTime":1244.82,"endTime":1249.82,"body":"Now, let's apply Bitcoin"},{"speaker":"And they do this using three technologies","startTime":1244.82,"endTime":1249.82,"body":"to Verona in 1597."},{"speaker":"And they do this using three technologies","startTime":1256.31,"endTime":1258.863,"body":"The story of Romeo and Juliet."},{"speaker":"And they do this using three technologies","startTime":1260.81,"endTime":1265.81,"body":"Now, Romeo and Juliet want to"},{"speaker":"And they do this using three technologies","startTime":1260.81,"endTime":1265.81,"body":"send letters to each other."},{"speaker":"And they do this using three technologies","startTime":1266.87,"endTime":1268.55,"body":"This is a dangerous thing,"},{"speaker":"And they do this using three technologies","startTime":1268.55,"endTime":1270.883,"body":"because their families are"},{"speaker":"And they do this using three technologies","startTime":1268.55,"endTime":1270.883,"body":"fighting with each other."},{"speaker":"And they do this using three technologies","startTime":1272.42,"endTime":1274.85,"body":"What problems do they face?"},{"speaker":"And they do this using three technologies","startTime":1274.85,"endTime":1277.7,"body":"Well, they need to be"},{"speaker":"And they do this using three technologies","startTime":1274.85,"endTime":1277.7,"body":"sure that no one else"},{"speaker":"And they do this using three technologies","startTime":1277.7,"endTime":1279.23,"body":"can read their letters,"},{"speaker":"And they do this using three technologies","startTime":1279.23,"endTime":1282.23,"body":"because they're not supposed"},{"speaker":"And they do this using three technologies","startTime":1279.23,"endTime":1282.23,"body":"to be writing to each other."},{"speaker":"And they do this using three technologies","startTime":1282.23,"endTime":1285.89,"body":"Second problem, they need"},{"speaker":"And they do this using three technologies","startTime":1282.23,"endTime":1285.89,"body":"to be sure that the letter"},{"speaker":"And they do this using three technologies","startTime":1285.89,"endTime":1288.32,"body":"is indubitably coming"},{"speaker":"And they do this using three technologies","startTime":1285.89,"endTime":1288.32,"body":"from only the two of them,"},{"speaker":"And they do this using three technologies","startTime":1288.32,"endTime":1292.58,"body":"is not being forged, for example,"},{"speaker":"And they do this using three technologies","startTime":1288.32,"endTime":1292.58,"body":"by Juliet's cousin Tybalt"},{"speaker":"And they do this using three technologies","startTime":1292.58,"endTime":1296.6,"body":"just to entrap Romeo"},{"speaker":"And they do this using three technologies","startTime":1292.58,"endTime":1296.6,"body":"into coming to some place"},{"speaker":"And they do this using three technologies","startTime":1296.6,"endTime":1297.75,"body":"and then murdering him."},{"speaker":"And they do this using three technologies","startTime":1298.61,"endTime":1302.51,"body":"Fine, even if someone else gets a letter,"},{"speaker":"And they do this using three technologies","startTime":1302.51,"endTime":1305.933,"body":"they should not be able to"},{"speaker":"And they do this using three technologies","startTime":1302.51,"endTime":1305.933,"body":"identify who the sender is."},{"speaker":"And they do this using three technologies","startTime":1307.73,"endTime":1310.76,"body":"Number four, the letter"},{"speaker":"And they do this using three technologies","startTime":1307.73,"endTime":1310.76,"body":"should not be garbled"},{"speaker":"And they do this using three technologies","startTime":1310.76,"endTime":1312.803,"body":"while the sending process is going on."},{"speaker":"And they do this using three technologies","startTime":1314.03,"endTime":1318.35,"body":"And number five, both Romeo"},{"speaker":"And they do this using three technologies","startTime":1314.03,"endTime":1318.35,"body":"and Juliet need to be sure"},{"speaker":"And they do this using three technologies","startTime":1318.35,"endTime":1320.84,"body":"that the Romeo or"},{"speaker":"And they do this using three technologies","startTime":1318.35,"endTime":1320.84,"body":"Juliet, the other person,"},{"speaker":"And they do this using three technologies","startTime":1320.84,"endTime":1323.993,"body":"is not writing the same letter"},{"speaker":"And they do this using three technologies","startTime":1320.84,"endTime":1323.993,"body":"to five other girls or boys,"},{"speaker":"And they do this using three technologies","startTime":1325.25,"endTime":1327.35,"body":"These are all important things."},{"speaker":"And they do this using three technologies","startTime":1327.35,"endTime":1330.353,"body":"You can see they all"},{"speaker":"And they do this using three technologies","startTime":1327.35,"endTime":1330.353,"body":"work for a blockchain."},{"speaker":"And they do this using three technologies","startTime":1331.37,"endTime":1333.5,"body":"We have anonymity."},{"speaker":"And they do this using three technologies","startTime":1333.5,"endTime":1337.34,"body":"We have over here completely"},{"speaker":"And they do this using three technologies","startTime":1333.5,"endTime":1337.34,"body":"unstructured data."},{"speaker":"And they do this using three technologies","startTime":1337.34,"endTime":1338.93,"body":"We'll talk about that in a bit."},{"speaker":"And they do this using three technologies","startTime":1338.93,"endTime":1340.88,"body":"And you want to make sure"},{"speaker":"And they do this using three technologies","startTime":1340.88,"endTime":1342.38,"body":"that there's no double spending."},{"speaker":"And they do this using three technologies","startTime":1342.38,"endTime":1345.13,"body":"You don't send the same letter"},{"speaker":"And they do this using three technologies","startTime":1342.38,"endTime":1345.13,"body":"to five different girls."},{"speaker":"And they do this using three technologies","startTime":1346.01,"endTime":1347.813,"body":"So, how do they do this problem?"},{"speaker":"And they do this using three technologies","startTime":1349.01,"endTime":1352.103,"body":"Well, let's address each"},{"speaker":"And they do this using three technologies","startTime":1349.01,"endTime":1352.103,"body":"of the problems one by one."},{"speaker":"There's problem number one","startTime":1354.56,"endTime":1357.38,"body":"no one else should be"},{"speaker":"There's problem number one","startTime":1354.56,"endTime":1357.38,"body":"able to read the letter."},{"speaker":"There's problem number one","startTime":1357.38,"endTime":1359.18,"body":"How do you do that?"},{"speaker":"There's problem number one","startTime":1359.18,"endTime":1362.363,"body":"Well, I'm going to"},{"speaker":"There's problem number one","startTime":1359.18,"endTime":1362.363,"body":"introduce Juliet's lockbox."},{"speaker":"There's problem number one","startTime":1363.38,"endTime":1365.333,"body":"This is a lockbox."},{"speaker":"There's problem number one","startTime":1366.171,"endTime":1368.03,"body":"In a typical lockbox, you have a key."},{"speaker":"There's problem number one","startTime":1368.03,"endTime":1370.37,"body":"You put your valuable"},{"speaker":"There's problem number one","startTime":1368.03,"endTime":1370.37,"body":"stuff inside a lockbox,"},{"speaker":"There's problem number one","startTime":1370.37,"endTime":1371.543,"body":"and you lock the box."},{"speaker":"There's problem number one","startTime":1372.44,"endTime":1374.12,"body":"You're the only person with a key."},{"speaker":"There's problem number one","startTime":1374.12,"endTime":1376.28,"body":"Technically, you're the"},{"speaker":"There's problem number one","startTime":1374.12,"endTime":1376.28,"body":"only person who can go"},{"speaker":"There's problem number one","startTime":1376.28,"endTime":1378.83,"body":"into the lockbox and take your stuff out."},{"speaker":"There's problem number one","startTime":1378.83,"endTime":1382.25,"body":"That's what we call"},{"speaker":"There's problem number one","startTime":1378.83,"endTime":1382.25,"body":"symmetric key cryptography."},{"speaker":"There's problem number one","startTime":1382.25,"endTime":1385.64,"body":"The only one key, one person,"},{"speaker":"There's problem number one","startTime":1382.25,"endTime":1385.64,"body":"one way to unlock the box,"},{"speaker":"There's problem number one","startTime":1385.64,"endTime":1386.99,"body":"and that's fine."},{"speaker":"There's problem number one","startTime":1386.99,"endTime":1389.183,"body":"But this box is very special."},{"speaker":"There's problem number one","startTime":1390.26,"endTime":1393.29,"body":"This reason it is special"},{"speaker":"There's problem number one","startTime":1390.26,"endTime":1393.29,"body":"is because it has two keys,"},{"speaker":"There's problem number one","startTime":1393.29,"endTime":1397.97,"body":"not one, and the two keys"},{"speaker":"There's problem number one","startTime":1393.29,"endTime":1397.97,"body":"work in different directions."},{"speaker":"There's problem number one","startTime":1397.97,"endTime":1401.213,"body":"What does that mean?"},{"speaker":"There's problem number one","startTime":1397.97,"endTime":1401.213,"body":"Well, let's take a look."},{"speaker":"There's problem number one","startTime":1403.73,"endTime":1406.94,"body":"First key can only turn clockwise."},{"speaker":"There's problem number one","startTime":1406.94,"endTime":1408.707,"body":"It cannot turn anti-clockwise"},{"speaker":"There's problem number one","startTime":1408.707,"endTime":1411.32,"body":"and only turn in the clockwise direction,"},{"speaker":"There's problem number one","startTime":1411.32,"endTime":1415.4,"body":"which means you can go from A to B to C."},{"speaker":"There's problem number one","startTime":1415.4,"endTime":1416.6,"body":"That's it."},{"speaker":"There's problem number one","startTime":1416.6,"endTime":1419.48,"body":"The second key can only"},{"speaker":"There's problem number one","startTime":1416.6,"endTime":1419.48,"body":"turn anti-clockwise"},{"speaker":"There's problem number one","startTime":1419.48,"endTime":1421.28,"body":"from C to B to A."},{"speaker":"There's problem number one","startTime":1421.28,"endTime":1423.11,"body":"It can't go the other way."},{"speaker":"There's problem number one","startTime":1423.11,"endTime":1428.11,"body":"So, two keys. Each one can"},{"speaker":"There's problem number one","startTime":1423.11,"endTime":1428.11,"body":"turn in one direction only."},{"speaker":"There's problem number one","startTime":1428.3,"endTime":1429.74,"body":"Fine."},{"speaker":"There's problem number one","startTime":1429.74,"endTime":1431.3,"body":"What good is that?"},{"speaker":"There's problem number one","startTime":1431.3,"endTime":1433.76,"body":"Let's say Juliet has this lockbox."},{"speaker":"There's problem number one","startTime":1433.76,"endTime":1435.56,"body":"She keeps one of the keys for herself."},{"speaker":"There's problem number one","startTime":1435.56,"endTime":1436.823,"body":"That's her private key."},{"speaker":"There's problem number one","startTime":1437.66,"endTime":1440.84,"body":"The key basically, let's"},{"speaker":"There's problem number one","startTime":1437.66,"endTime":1440.84,"body":"say, is the clockwise key."},{"speaker":"There's problem number one","startTime":1440.84,"endTime":1443.93,"body":"She gets it from A to B to C."},{"speaker":"There's problem number one","startTime":1443.93,"endTime":1446.96,"body":"That's the only direction"},{"speaker":"There's problem number one","startTime":1443.93,"endTime":1446.96,"body":"her key can turn."},{"speaker":"There's problem number one","startTime":1446.96,"endTime":1448.79,"body":"What about the other key?"},{"speaker":"There's problem number one","startTime":1448.79,"endTime":1450.65,"body":"Well, she makes 1000 copies of that key."},{"speaker":"There's problem number one","startTime":1450.65,"endTime":1452.84,"body":"She distributes it to everybody."},{"speaker":"There's problem number one","startTime":1452.84,"endTime":1455.15,"body":"She hangs some outside her balcony."},{"speaker":"There's problem number one","startTime":1455.15,"endTime":1457.88,"body":"If you want to, if you ask"},{"speaker":"There's problem number one","startTime":1455.15,"endTime":1457.88,"body":"her for a business card,"},{"speaker":"There's problem number one","startTime":1457.88,"endTime":1459.68,"body":"she'll take a key out and give it to you."},{"speaker":"There's problem number one","startTime":1459.68,"endTime":1461.3,"body":"She's got a million copies of the key."},{"speaker":"There's problem number one","startTime":1461.3,"endTime":1464.0,"body":"Everyone can get a copy of"},{"speaker":"There's problem number one","startTime":1461.3,"endTime":1464.0,"body":"the key whenever they want."},{"speaker":"There's problem number one","startTime":1465.05,"endTime":1468.74,"body":"Fine. What good is it now?"},{"speaker":"There's problem number one","startTime":1468.74,"endTime":1473.74,"body":"Well, let's say Romeo wants"},{"speaker":"There's problem number one","startTime":1468.74,"endTime":1473.74,"body":"to send Juliet a letter."},{"speaker":"There's problem number one","startTime":1474.44,"endTime":1476.54,"body":"He wants to be sure that"},{"speaker":"There's problem number one","startTime":1474.44,"endTime":1476.54,"body":"no one else should be able"},{"speaker":"There's problem number one","startTime":1476.54,"endTime":1477.95,"body":"to read the letter."},{"speaker":"There's problem number one","startTime":1477.95,"endTime":1479.21,"body":"What does he do?"},{"speaker":"There's problem number one","startTime":1479.21,"endTime":1481.82,"body":"Juliet's lockbox is outside her balcony,"},{"speaker":"There's problem number one","startTime":1481.82,"endTime":1483.56,"body":"easily accessible,"},{"speaker":"There's problem number one","startTime":1483.56,"endTime":1485.56,"body":"at least in the Romeo and Julia stories."},{"speaker":"There's problem number one","startTime":1486.86,"endTime":1489.26,"body":"You go to the lockbox,"},{"speaker":"There's problem number one","startTime":1486.86,"endTime":1489.26,"body":"you take your letter,"},{"speaker":"There's problem number one","startTime":1489.26,"endTime":1491.12,"body":"you put it inside the lockbox,"},{"speaker":"There's problem number one","startTime":1491.12,"endTime":1494.18,"body":"and you lock it with Juliet's public key,"},{"speaker":"There's problem number one","startTime":1494.18,"endTime":1495.83,"body":"which he's been giving everybody."},{"speaker":"There's problem number one","startTime":1496.67,"endTime":1500.3,"body":"The public key, remember,"},{"speaker":"There's problem number one","startTime":1496.67,"endTime":1500.3,"body":"can only turn anti-clockwise."},{"speaker":"There's problem number one","startTime":1500.3,"endTime":1501.77,"body":"From the unlocked position,"},{"speaker":"There's problem number one","startTime":1501.77,"endTime":1505.22,"body":"it can only go to position A,"},{"speaker":"There's problem number one","startTime":1501.77,"endTime":1505.22,"body":"it cannot go to position C."},{"speaker":"There's problem number one","startTime":1505.22,"endTime":1507.847,"body":"Position C would be clockwise."},{"speaker":"There's problem number one","startTime":1507.847,"endTime":1511.04,"body":"You have locked it. Now,"},{"speaker":"There's problem number one","startTime":1507.847,"endTime":1511.04,"body":"who can unlock this?"},{"speaker":"There's problem number one","startTime":1511.04,"endTime":1512.87,"body":"Nobody else who has Juliet's public key,"},{"speaker":"There's problem number one","startTime":1512.87,"endTime":1517.07,"body":"because the public key, remember,"},{"speaker":"There's problem number one","startTime":1512.87,"endTime":1517.07,"body":"only turns anti-clockwise."},{"speaker":"There's problem number one","startTime":1517.07,"endTime":1518.66,"body":"If it's locked in this position,"},{"speaker":"There's problem number one","startTime":1518.66,"endTime":1521.72,"body":"anti-clockwise would mean"},{"speaker":"There's problem number one","startTime":1518.66,"endTime":1521.72,"body":"trying to force it down"},{"speaker":"There's problem number one","startTime":1521.72,"endTime":1523.52,"body":"to come here, which wouldn't happen."},{"speaker":"There's problem number one","startTime":1524.48,"endTime":1528.62,"body":"The only person who can"},{"speaker":"There's problem number one","startTime":1524.48,"endTime":1528.62,"body":"unlock the box is Juliet,"},{"speaker":"There's problem number one","startTime":1528.62,"endTime":1531.41,"body":"because she's the only"},{"speaker":"There's problem number one","startTime":1528.62,"endTime":1531.41,"body":"one with a private key,"},{"speaker":"There's problem number one","startTime":1531.41,"endTime":1533.42,"body":"which goes in the clockwise direction."},{"speaker":"There's problem number one","startTime":1533.42,"endTime":1536.81,"body":"She can put her key in"},{"speaker":"There's problem number one","startTime":1533.42,"endTime":1536.81,"body":"the lock and unlock it,"},{"speaker":"There's problem number one","startTime":1536.81,"endTime":1539.21,"body":"so can make sure that"},{"speaker":"There's problem number one","startTime":1536.81,"endTime":1539.21,"body":"Juliet is the only one"},{"speaker":"There's problem number one","startTime":1539.21,"endTime":1540.11,"body":"who reads the key."},{"speaker":"There's problem number one","startTime":1541.07,"endTime":1542.02,"body":"Problem number one."},{"speaker":"Problem number two","startTime":1542.96,"endTime":1547.96,"body":"basically,"},{"speaker":"Problem number two","startTime":1542.96,"endTime":1547.96,"body":"Romeo needs to be sure"},{"speaker":"Problem number two","startTime":1548.78,"endTime":1551.48,"body":"that this letter, which"},{"speaker":"Problem number two","startTime":1548.78,"endTime":1551.48,"body":"he's getting in response,"},{"speaker":"Problem number two","startTime":1551.48,"endTime":1553.61,"body":"is actually from Juliet."},{"speaker":"Problem number two","startTime":1553.61,"endTime":1554.93,"body":"How do you do that?"},{"speaker":"Problem number two","startTime":1554.93,"endTime":1557.783,"body":"Well, that's what we"},{"speaker":"Problem number two","startTime":1554.93,"endTime":1557.783,"body":"call a digital signature."},{"speaker":"Problem number two","startTime":1558.914,"endTime":1562.43,"body":"Juliet now is sending a"},{"speaker":"Problem number two","startTime":1558.914,"endTime":1562.43,"body":"response back to Romeo"},{"speaker":"Problem number two","startTime":1562.43,"endTime":1563.66,"body":"in the same lockbox."},{"speaker":"Problem number two","startTime":1563.66,"endTime":1565.01,"body":"What does she do?"},{"speaker":"Problem number two","startTime":1565.01,"endTime":1569.18,"body":"She puts her response on the"},{"speaker":"Problem number two","startTime":1565.01,"endTime":1569.18,"body":"lockbox and she locks it."},{"speaker":"Problem number two","startTime":1569.18,"endTime":1572.21,"body":"The problem of course is"},{"speaker":"Problem number two","startTime":1569.18,"endTime":1572.21,"body":"Romeo wants to be sure"},{"speaker":"Problem number two","startTime":1572.21,"endTime":1575.18,"body":"that this letter is actually from Juliet."},{"speaker":"Problem number two","startTime":1575.18,"endTime":1577.04,"body":"Because it could be a forgery,"},{"speaker":"Problem number two","startTime":1577.04,"endTime":1578.937,"body":"it could be a letter"},{"speaker":"Problem number two","startTime":1577.04,"endTime":1578.937,"body":"sent by Tybalt saying,"},{"speaker":"Problem number two","startTime":1578.937,"endTime":1581.537,"body":"\"Come to the crypt at midnight.\""},{"speaker":"Problem number two","startTime":1582.68,"endTime":1584.51,"body":"And you go to the crypt at midnight,"},{"speaker":"Problem number two","startTime":1584.51,"endTime":1586.85,"body":"he's waiting for you"},{"speaker":"Problem number two","startTime":1584.51,"endTime":1586.85,"body":"with a knife in his hand,"},{"speaker":"Problem number two","startTime":1586.85,"endTime":1590.15,"body":"stabs you in the stomach,"},{"speaker":"Problem number two","startTime":1586.85,"endTime":1590.15,"body":"and life is all over."},{"speaker":"Problem number two","startTime":1590.15,"endTime":1592.15,"body":"It happens a lot in Shakespeare's plays."},{"speaker":"Problem number two","startTime":1593.6,"endTime":1595.7,"body":"And of course, Juliet wants be sure"},{"speaker":"Problem number two","startTime":1595.7,"endTime":1597.17,"body":"that Romeo trusts her letter,"},{"speaker":"Problem number two","startTime":1597.17,"endTime":1600.44,"body":"because there's nothing worse"},{"speaker":"Problem number two","startTime":1597.17,"endTime":1600.44,"body":"than someone showing up."},{"speaker":"Problem number two","startTime":1600.44,"endTime":1602.84,"body":"A young, unmarried girl showing"},{"speaker":"Problem number two","startTime":1600.44,"endTime":1602.84,"body":"up in a crypt at midnight,"},{"speaker":"Problem number two","startTime":1602.84,"endTime":1604.28,"body":"and your boyfriend is not there."},{"speaker":"Problem number two","startTime":1604.28,"endTime":1607.01,"body":"That's dangerous as well. You"},{"speaker":"Problem number two","startTime":1604.28,"endTime":1607.01,"body":"don't want that to happen."},{"speaker":"Problem number two","startTime":1607.01,"endTime":1608.81,"body":"Both of them need to"},{"speaker":"Problem number two","startTime":1607.01,"endTime":1608.81,"body":"be sure that the letter"},{"speaker":"Problem number two","startTime":1608.81,"endTime":1612.5,"body":"is indeed from Juliet."},{"speaker":"Problem number two","startTime":1612.5,"endTime":1615.86,"body":"What she does is takes"},{"speaker":"Problem number two","startTime":1612.5,"endTime":1615.86,"body":"her key, her private key,"},{"speaker":"Problem number two","startTime":1615.86,"endTime":1617.51,"body":"and she locks the box."},{"speaker":"Problem number two","startTime":1617.51,"endTime":1620.573,"body":"Now, private key only turns clockwise."},{"speaker":"Problem number two","startTime":1621.5,"endTime":1626.03,"body":"She sticks it in the lock,"},{"speaker":"Problem number two","startTime":1621.5,"endTime":1626.03,"body":"locks it clockwise, position C."},{"speaker":"Problem number two","startTime":1626.03,"endTime":1627.77,"body":"Now, who can unlock it?"},{"speaker":"Problem number two","startTime":1627.77,"endTime":1630.47,"body":"Only someone with Juliet's public key,"},{"speaker":"Problem number two","startTime":1630.47,"endTime":1633.42,"body":"because that's the only key"},{"speaker":"Problem number two","startTime":1630.47,"endTime":1633.42,"body":"which will turn anti-clockwise,"},{"speaker":"Problem number two","startTime":1634.91,"endTime":1638.33,"body":"if you try to turn it the"},{"speaker":"Problem number two","startTime":1634.91,"endTime":1638.33,"body":"other way, it won't unlock."},{"speaker":"Problem number two","startTime":1638.33,"endTime":1639.65,"body":"If you have her public key though,"},{"speaker":"Problem number two","startTime":1639.65,"endTime":1642.623,"body":"you can go from here,"},{"speaker":"Problem number two","startTime":1639.65,"endTime":1642.623,"body":"anti-clockwise, turn it back."},{"speaker":"Problem number two","startTime":1643.73,"endTime":1647.48,"body":"That private key locking is"},{"speaker":"Problem number two","startTime":1643.73,"endTime":1647.48,"body":"called a digital signature."},{"speaker":"Problem number two","startTime":1647.48,"endTime":1650.54,"body":"If you encrypt a message"},{"speaker":"Problem number two","startTime":1647.48,"endTime":1650.54,"body":"with your private key,"},{"speaker":"Problem number two","startTime":1650.54,"endTime":1653.75,"body":"that's guaranteed that that"},{"speaker":"Problem number two","startTime":1650.54,"endTime":1653.75,"body":"message comes from you."},{"speaker":"Problem number two","startTime":1653.75,"endTime":1655.97,"body":"That, by the way, is why people know"},{"speaker":"Problem number two","startTime":1655.97,"endTime":1659.36,"body":"there's nobody who's"},{"speaker":"Problem number two","startTime":1655.97,"endTime":1659.36,"body":"actually Satoshi Nakamoto,"},{"speaker":"Problem number two","startTime":1659.36,"endTime":1661.85,"body":"because no one's been"},{"speaker":"Problem number two","startTime":1659.36,"endTime":1661.85,"body":"able to unlock any message"},{"speaker":"Problem number two","startTime":1661.85,"endTime":1664.25,"body":"with Satoshi Nakamoto's private key."},{"speaker":"Problem number two","startTime":1664.25,"endTime":1665.96,"body":"Either they've lost the private key,"},{"speaker":"Problem number two","startTime":1665.96,"endTime":1667.16,"body":"or it just doesn't exist."},{"speaker":"Problem number two","startTime":1667.16,"endTime":1668.72,"body":"If you do not have his private key,"},{"speaker":"Problem number two","startTime":1668.72,"endTime":1671.87,"body":"you cannot prove that"},{"speaker":"Problem number two","startTime":1668.72,"endTime":1671.87,"body":"you're Satoshi Nakamoto."},{"speaker":"Problem number two","startTime":1671.87,"endTime":1673.55,"body":"Anyway but that's weird."},{"speaker":"Problem number two","startTime":1673.55,"endTime":1677.66,"body":"I mean, excuse me, anyone"},{"speaker":"Problem number two","startTime":1673.55,"endTime":1677.66,"body":"can unlock that box now."},{"speaker":"Problem number two","startTime":1677.66,"endTime":1679.82,"body":"Anyone who has a public key."},{"speaker":"Problem number two","startTime":1679.82,"endTime":1682.37,"body":"How do you make sure the"},{"speaker":"Problem number two","startTime":1679.82,"endTime":1682.37,"body":"problem number three?"},{"speaker":"Problem number two","startTime":1682.37,"endTime":1683.48,"body":"Problem number three is,"},{"speaker":"Problem number two","startTime":1683.48,"endTime":1685.73,"body":"even if someone does"},{"speaker":"Problem number two","startTime":1683.48,"endTime":1685.73,"body":"intercept the lockbox,"},{"speaker":"Problem number two","startTime":1685.73,"endTime":1688.97,"body":"they shouldn't know, they"},{"speaker":"Problem number two","startTime":1685.73,"endTime":1688.97,"body":"couldn't be able to decrypt,"},{"speaker":"Problem number two","startTime":1688.97,"endTime":1691.25,"body":"find out the identity of the sender."},{"speaker":"Problem number two","startTime":1691.25,"endTime":1692.45,"body":"What do you do?"},{"speaker":"Problem number two","startTime":1692.45,"endTime":1695.69,"body":"Well, Juliet again, she has a lockbox."},{"speaker":"Problem number two","startTime":1695.69,"endTime":1698.57,"body":"She puts her letter inside the lockbox,"},{"speaker":"Problem number two","startTime":1698.57,"endTime":1701.57,"body":"she locks it using her private key."},{"speaker":"Problem number two","startTime":1701.57,"endTime":1704.12,"body":"Now, anyone unlocking it with a public key"},{"speaker":"Problem number two","startTime":1704.12,"endTime":1705.62,"body":"will know when is come Juliet,"},{"speaker":"Problem number two","startTime":1706.61,"endTime":1708.38,"body":"But I don't want any anyone to open it."},{"speaker":"Problem number two","startTime":1708.38,"endTime":1712.49,"body":"I want only Romeo to open"},{"speaker":"Problem number two","startTime":1708.38,"endTime":1712.49,"body":"it. How do I ensure that?"},{"speaker":"Problem number two","startTime":1712.49,"endTime":1714.77,"body":"Well, I put it into a second lockbox,"},{"speaker":"Problem number two","startTime":1714.77,"endTime":1717.5,"body":"and the second lockbox is"},{"speaker":"Problem number two","startTime":1714.77,"endTime":1717.5,"body":"the one belonging to Romeo,"},{"speaker":"Problem number two","startTime":1717.5,"endTime":1720.203,"body":"and I lock that using Romeo's public key."},{"speaker":"Problem number two","startTime":1721.88,"endTime":1723.98,"body":"Essentially, Romeo is"},{"speaker":"Problem number two","startTime":1721.88,"endTime":1723.98,"body":"the only one who's able"},{"speaker":"Problem number two","startTime":1723.98,"endTime":1727.01,"body":"to open the outer lockbox"},{"speaker":"Problem number two","startTime":1723.98,"endTime":1727.01,"body":"with his private key."},{"speaker":"Problem number two","startTime":1727.01,"endTime":1729.65,"body":"Inside that lockbox, he"},{"speaker":"Problem number two","startTime":1727.01,"endTime":1729.65,"body":"finds a second lockbox,"},{"speaker":"Problem number two","startTime":1729.65,"endTime":1732.47,"body":"which can only be opened"},{"speaker":"Problem number two","startTime":1729.65,"endTime":1732.47,"body":"with Juliet's public key."},{"speaker":"Problem number two","startTime":1732.47,"endTime":1736.34,"body":"Now, I know that that letter"},{"speaker":"Problem number two","startTime":1732.47,"endTime":1736.34,"body":"inside comes from Juliet,"},{"speaker":"Problem number two","startTime":1736.34,"endTime":1739.043,"body":"and Romeo is the only one"},{"speaker":"Problem number two","startTime":1736.34,"endTime":1739.043,"body":"who can receive that letter."},{"speaker":"Problem number two","startTime":1740.09,"endTime":1743.363,"body":"So that's problems one,"},{"speaker":"Problem number two","startTime":1740.09,"endTime":1743.363,"body":"two, and three is solved."},{"speaker":"Problem number two","startTime":1744.38,"endTime":1747.74,"body":"But how do you make such keys?"},{"speaker":"Problem number two","startTime":1747.74,"endTime":1750.11,"body":"The answer is mathematics."},{"speaker":"Problem number two","startTime":1750.11,"endTime":1752.93,"body":"Let me ask you guys a simple question."},{"speaker":"Problem number two","startTime":1752.93,"endTime":1757.25,"body":"What is 17959 times 33851?"},{"speaker":"Problem number two","startTime":1757.25,"endTime":1758.78,"body":"How much time do you think it'll take you"},{"speaker":"Problem number two","startTime":1758.78,"endTime":1761.42,"body":"to get that answer, in"},{"speaker":"Problem number two","startTime":1758.78,"endTime":1761.42,"body":"today's day and age?"},{"speaker":"Problem number two","startTime":1761.42,"endTime":1762.38,"body":"10 seconds?"},{"speaker":"Problem number two","startTime":1762.38,"endTime":1765.32,"body":"All you do, pull your phone"},{"speaker":"Problem number two","startTime":1762.38,"endTime":1765.32,"body":"on, start the calculator,"},{"speaker":"Problem number two","startTime":1765.32,"endTime":1768.12,"body":"press a button, you give you"},{"speaker":"Problem number two","startTime":1765.32,"endTime":1768.12,"body":"the answer in five seconds."},{"speaker":"Problem number two","startTime":1769.94,"endTime":1771.62,"body":"How about this question?"},{"speaker":"Problem number two","startTime":1771.62,"endTime":1773.51,"body":"Is this a prime number?"},{"speaker":"Problem number two","startTime":1773.51,"endTime":1775.79,"body":"A prime number is a number"},{"speaker":"Problem number two","startTime":1773.51,"endTime":1775.79,"body":"that's only divisible"},{"speaker":"Problem number two","startTime":1775.79,"endTime":1777.08,"body":"by one or itself."},{"speaker":"Problem number two","startTime":1777.08,"endTime":1779.57,"body":"So three, five, seven are prime numbers."},{"speaker":"Problem number two","startTime":1779.57,"endTime":1782.39,"body":"Nine is not a prime number,"},{"speaker":"Problem number two","startTime":1779.57,"endTime":1782.39,"body":"because it's divisible by three"},{"speaker":"Problem number two","startTime":1782.39,"endTime":1785.87,"body":"in addition to being"},{"speaker":"Problem number two","startTime":1782.39,"endTime":1785.87,"body":"divisible by one and nine."},{"speaker":"Problem number two","startTime":1785.87,"endTime":1787.613,"body":"So, is this a prime number?"},{"speaker":"Problem number two","startTime":1789.53,"endTime":1791.09,"body":"I can guarantee,"},{"speaker":"Problem number two","startTime":1791.09,"endTime":1793.7,"body":"unless you've actually"},{"speaker":"Problem number two","startTime":1791.09,"endTime":1793.7,"body":"seen this number before,"},{"speaker":"Problem number two","startTime":1793.7,"endTime":1794.533,"body":"it's going to take you"},{"speaker":"Problem number two","startTime":1794.533,"endTime":1797.483,"body":"a very, very, very long"},{"speaker":"Problem number two","startTime":1794.533,"endTime":1797.483,"body":"time to figure this out."},{"speaker":"Problem number two","startTime":1798.35,"endTime":1800.69,"body":"The answer is, by the way,"},{"speaker":"Problem number two","startTime":1798.35,"endTime":1800.69,"body":"if you multiply the two,"},{"speaker":"Problem number two","startTime":1800.69,"endTime":1803.03,"body":"that's the number that takes"},{"speaker":"Problem number two","startTime":1800.69,"endTime":1803.03,"body":"10 seconds or five seconds,"},{"speaker":"Problem number two","startTime":1803.03,"endTime":1805.88,"body":"how much time it takes to"},{"speaker":"Problem number two","startTime":1803.03,"endTime":1805.88,"body":"type this in your calculator."},{"speaker":"Problem number two","startTime":1805.88,"endTime":1807.44,"body":"But this is not a prime number."},{"speaker":"Problem number two","startTime":1807.44,"endTime":1810.597,"body":"It's actually the product"},{"speaker":"Problem number two","startTime":1807.44,"endTime":1810.597,"body":"of two prime numbers."},{"speaker":"Problem number two","startTime":1810.597,"endTime":1814.34,"body":"These two are prime, but"},{"speaker":"Problem number two","startTime":1810.597,"endTime":1814.34,"body":"this is not a prime number."},{"speaker":"Problem number two","startTime":1814.34,"endTime":1819.34,"body":"Now, this is what"},{"speaker":"Problem number two","startTime":1814.34,"endTime":1819.34,"body":"cryptography consists of."},{"speaker":"Problem number two","startTime":1820.31,"endTime":1823.22,"body":"Basically, you have a public"},{"speaker":"Problem number two","startTime":1820.31,"endTime":1823.22,"body":"key consisting of two numbers."},{"speaker":"Problem number two","startTime":1823.22,"endTime":1824.81,"body":"Well, one number is a multiplication"},{"speaker":"Problem number two","startTime":1824.81,"endTime":1828.173,"body":"of two very, very, very"},{"speaker":"Problem number two","startTime":1824.81,"endTime":1828.173,"body":"large prime numbers."},{"speaker":"Problem number two","startTime":1829.16,"endTime":1831.86,"body":"That means in order to"},{"speaker":"Problem number two","startTime":1829.16,"endTime":1831.86,"body":"factorize these prime numbers,"},{"speaker":"Problem number two","startTime":1831.86,"endTime":1834.89,"body":"it's going to take you"},{"speaker":"Problem number two","startTime":1831.86,"endTime":1834.89,"body":"an enormously long time."},{"speaker":"Problem number two","startTime":1834.89,"endTime":1838.16,"body":"Most people, if you take"},{"speaker":"Problem number two","startTime":1834.89,"endTime":1838.16,"body":"sequential computers today,"},{"speaker":"Problem number two","startTime":1838.16,"endTime":1840.71,"body":"it will take you more time than exists"},{"speaker":"Problem number two","startTime":1840.71,"endTime":1843.29,"body":"in the entire universe"},{"speaker":"Problem number two","startTime":1840.71,"endTime":1843.29,"body":"since the universe has begun"},{"speaker":"Problem number two","startTime":1843.29,"endTime":1845.723,"body":"to actually factorize a number like this."},{"speaker":"Problem number two","startTime":1847.31,"endTime":1849.2,"body":"Of course, the private key is also derived"},{"speaker":"Problem number two","startTime":1849.2,"endTime":1850.46,"body":"to the same two prime numbers."},{"speaker":"Problem number two","startTime":1850.46,"endTime":1852.11,"body":"If you can factor a product,"},{"speaker":"Problem number two","startTime":1852.11,"endTime":1854.06,"body":"you know what the prime numbers are,"},{"speaker":"Problem number two","startTime":1854.06,"endTime":1855.92,"body":"you should be able to"},{"speaker":"Problem number two","startTime":1854.06,"endTime":1855.92,"body":"find out the private key."},{"speaker":"Problem number two","startTime":1855.92,"endTime":1859.28,"body":"If you use a small pair of prime numbers,"},{"speaker":"Problem number two","startTime":1859.28,"endTime":1860.87,"body":"it's easy to factorize."},{"speaker":"Problem number two","startTime":1860.87,"endTime":1864.08,"body":"The idea is you want a"},{"speaker":"Problem number two","startTime":1860.87,"endTime":1864.08,"body":"super long prime number."},{"speaker":"Problem number two","startTime":1864.08,"endTime":1866.753,"body":"Very difficult to"},{"speaker":"Problem number two","startTime":1864.08,"endTime":1866.753,"body":"factorize these products."},{"speaker":"Problem number two","startTime":1867.68,"endTime":1871.1,"body":"This holds, by the way, in the"},{"speaker":"Problem number two","startTime":1867.68,"endTime":1871.1,"body":"absence of quantum computing."},{"speaker":"Problem number two","startTime":1871.1,"endTime":1873.83,"body":"The story is that once you"},{"speaker":"Problem number two","startTime":1871.1,"endTime":1873.83,"body":"have quantum computing,"},{"speaker":"Problem number two","startTime":1873.83,"endTime":1876.38,"body":"that'll be equivalent of"},{"speaker":"Problem number two","startTime":1873.83,"endTime":1876.38,"body":"throwing millions of computers"},{"speaker":"Problem number two","startTime":1876.38,"endTime":1878.42,"body":"at the same problem, so it's possible"},{"speaker":"Problem number two","startTime":1878.42,"endTime":1880.01,"body":"to break that encryption."},{"speaker":"Problem number two","startTime":1880.01,"endTime":1882.147,"body":"But as yet, we don't"},{"speaker":"Problem number two","startTime":1880.01,"endTime":1882.147,"body":"have quantum computing."},{"speaker":"Problem number two","startTime":1882.147,"endTime":1884.24,"body":"This is a problem for the future."},{"speaker":"Problem number two","startTime":1884.24,"endTime":1887.18,"body":"People are working today on ways to solve"},{"speaker":"Problem number two","startTime":1887.18,"endTime":1889.31,"body":"the quantum encryption problem."},{"speaker":"Problem number two","startTime":1889.31,"endTime":1891.53,"body":"But coming back to our situation,"},{"speaker":"Problem number two","startTime":1891.53,"endTime":1893.48,"body":"we have solved these three problems."},{"speaker":"Problem number two","startTime":1893.48,"endTime":1895.61,"body":"Juliet needs to be sure that no one else"},{"speaker":"Problem number two","startTime":1895.61,"endTime":1896.45,"body":"can read their letters."},{"speaker":"Problem number two","startTime":1896.45,"endTime":1898.73,"body":"You'd be sure the letter"},{"speaker":"Problem number two","startTime":1896.45,"endTime":1898.73,"body":"is coming from one of them,"},{"speaker":"Problem number two","startTime":1898.73,"endTime":1902.18,"body":"even if someone else gets the"},{"speaker":"Problem number two","startTime":1898.73,"endTime":1902.18,"body":"letter, the sender is secret."},{"speaker":"Problem number two","startTime":1902.18,"endTime":1905.96,"body":"Now the letters shouldn't"},{"speaker":"Problem number two","startTime":1902.18,"endTime":1905.96,"body":"be garbled before sending,"},{"speaker":"Problem number two","startTime":1905.96,"endTime":1907.91,"body":"and of course they need to be sure"},{"speaker":"Problem number two","startTime":1907.91,"endTime":1909.92,"body":"that they're not writing the same letter"},{"speaker":"Problem number two","startTime":1909.92,"endTime":1911.45,"body":"to five other people."},{"speaker":"Problem number two","startTime":1911.45,"endTime":1912.683,"body":"How do you do those two?"},{"speaker":"Problem number two","startTime":1913.64,"endTime":1916.643,"body":"Well, let's take a look at problem four."},{"speaker":"Problem number two","startTime":1918.71,"endTime":1922.04,"body":"If you think about a king"},{"speaker":"Problem number two","startTime":1918.71,"endTime":1922.04,"body":"in the medieval ages,"},{"speaker":"Problem number two","startTime":1922.04,"endTime":1924.41,"body":"for example, who wants to send a message"},{"speaker":"Problem number two","startTime":1924.41,"endTime":1926.675,"body":"to his general on the battlefield."},{"speaker":"Problem number two","startTime":1926.675,"endTime":1931.34,"body":"He might write him a sentence"},{"speaker":"Problem number two","startTime":1926.675,"endTime":1931.34,"body":"saying, \"Attack at dawn.\""},{"speaker":"Problem number two","startTime":1931.34,"endTime":1933.98,"body":"You write a letter, give it"},{"speaker":"Problem number two","startTime":1931.34,"endTime":1933.98,"body":"to your trusted messenger."},{"speaker":"Problem number two","startTime":1933.98,"endTime":1936.657,"body":"He rides across to the"},{"speaker":"Problem number two","startTime":1933.98,"endTime":1936.657,"body":"general, gives him the message,"},{"speaker":"Problem number two","startTime":1936.657,"endTime":1938.33,"body":"\"Attack at dawn.\""},{"speaker":"Problem number two","startTime":1938.33,"endTime":1939.62,"body":"What are the problems?"},{"speaker":"Problem number two","startTime":1939.62,"endTime":1941.84,"body":"Maybe the messenger is"},{"speaker":"Problem number two","startTime":1939.62,"endTime":1941.84,"body":"galloping across the field,"},{"speaker":"Problem number two","startTime":1941.84,"endTime":1943.37,"body":"the horse breaks a leg,"},{"speaker":"Problem number two","startTime":1943.37,"endTime":1945.92,"body":"messenger breaks his neck,"},{"speaker":"Problem number two","startTime":1943.37,"endTime":1945.92,"body":"message never gets read."},{"speaker":"Problem number two","startTime":1947.12,"endTime":1950.48,"body":"Second problem, maybe the"},{"speaker":"Problem number two","startTime":1947.12,"endTime":1950.48,"body":"messenger is intercepted,"},{"speaker":"Problem number two","startTime":1950.48,"endTime":1951.68,"body":"his message is replaced."},{"speaker":"Problem number two","startTime":1951.68,"endTime":1954.06,"body":"But the second message"},{"speaker":"Problem number two","startTime":1951.68,"endTime":1954.06,"body":"from the enemy saying,"},{"speaker":"Problem number two","startTime":1954.06,"endTime":1956.93,"body":"instead of attack at"},{"speaker":"Problem number two","startTime":1954.06,"endTime":1956.93,"body":"dawn, \"Retreat at once.\""},{"speaker":"Problem number two","startTime":1956.93,"endTime":1960.44,"body":"So the general retreats,"},{"speaker":"Problem number two","startTime":1956.93,"endTime":1960.44,"body":"instead of attacking."},{"speaker":"Problem number two","startTime":1960.44,"endTime":1961.82,"body":"How do you solve this problem?"},{"speaker":"Problem number two","startTime":1961.82,"endTime":1962.93,"body":"Well, easy way."},{"speaker":"Problem number two","startTime":1962.93,"endTime":1965.393,"body":"You send 20 of messengers. Not one, 20."},{"speaker":"Problem number two","startTime":1966.38,"endTime":1969.05,"body":"And some of them, they"},{"speaker":"Problem number two","startTime":1966.38,"endTime":1969.05,"body":"all take different route."},{"speaker":"Problem number two","startTime":1969.05,"endTime":1970.64,"body":"The general comes, gets a message."},{"speaker":"Problem number two","startTime":1970.64,"endTime":1975.14,"body":"Gets maybe 16 messages of"},{"speaker":"Problem number two","startTime":1970.64,"endTime":1975.14,"body":"which 14 say, \"Attack at dawn,\""},{"speaker":"Problem number two","startTime":1975.14,"endTime":1978.2,"body":"two say, \"Retreat at once,\""},{"speaker":"Problem number two","startTime":1975.14,"endTime":1978.2,"body":"and two never show up."},{"speaker":"Problem number two","startTime":1978.2,"endTime":1979.79,"body":"He knows 20 messages been sent."},{"speaker":"Problem number two","startTime":1979.79,"endTime":1982.91,"body":"So he says, \"Well, I think it"},{"speaker":"Problem number two","startTime":1979.79,"endTime":1982.91,"body":"is basically attack at dawn,"},{"speaker":"Problem number two","startTime":1982.91,"endTime":1985.79,"body":"because that's the majority"},{"speaker":"Problem number two","startTime":1982.91,"endTime":1985.79,"body":"of all the messages.\""},{"speaker":"Problem number two","startTime":1985.79,"endTime":1988.61,"body":"Unfortunately, this"},{"speaker":"Problem number two","startTime":1985.79,"endTime":1988.61,"body":"doesn't work for Romeo,"},{"speaker":"Problem number two","startTime":1988.61,"endTime":1990.68,"body":"because Romeo is a romantic."},{"speaker":"Problem number two","startTime":1990.68,"endTime":1994.76,"body":"He's not going to write"},{"speaker":"Problem number two","startTime":1990.68,"endTime":1994.76,"body":"a three word message."},{"speaker":"Problem number two","startTime":1994.76,"endTime":1997.04,"body":"He's not even going to write a sonnet."},{"speaker":"Problem number two","startTime":1997.04,"endTime":2001.9,"body":"He's going to write a giant"},{"speaker":"Problem number two","startTime":1997.04,"endTime":2001.9,"body":"thousand verse stanza."},{"speaker":"Problem number two","startTime":2001.9,"endTime":2004.09,"body":"Something like the"},{"speaker":"Problem number two","startTime":2001.9,"endTime":2004.09,"body":"Mahabharata or the Iliad."},{"speaker":"Problem number two","startTime":2004.09,"endTime":2005.59,"body":"Massive poem."},{"speaker":"Problem number two","startTime":2005.59,"endTime":2008.92,"body":"And it has to be perfect. You"},{"speaker":"Problem number two","startTime":2005.59,"endTime":2008.92,"body":"can't get a single word wrong."},{"speaker":"Problem number two","startTime":2008.92,"endTime":2011.68,"body":"If you say, \"Shall I compare"},{"speaker":"Problem number two","startTime":2008.92,"endTime":2011.68,"body":"the to a summer's day?\""},{"speaker":"Problem number two","startTime":2011.68,"endTime":2013.153,"body":"And it works out to be,"},{"speaker":"Problem number two","startTime":2014.237,"endTime":2016.18,"body":"\"My idol has feet of clay,\""},{"speaker":"Problem number two","startTime":2016.18,"endTime":2018.25,"body":"they're very different from each other."},{"speaker":"Problem number two","startTime":2018.25,"endTime":2020.32,"body":"We don't want to send the second message"},{"speaker":"Problem number two","startTime":2020.32,"endTime":2022.3,"body":"when you can only send the first message."},{"speaker":"Problem number two","startTime":2022.3,"endTime":2024.223,"body":"So how does you solve that problem?"},{"speaker":"Problem number two","startTime":2025.45,"endTime":2027.043,"body":"The answer is hashing."},{"speaker":"Problem number two","startTime":2028.058,"endTime":2029.89,"body":"What we're going to do with hashing"},{"speaker":"Problem number two","startTime":2029.89,"endTime":2034.45,"body":"is construct a summary of the"},{"speaker":"Problem number two","startTime":2029.89,"endTime":2034.45,"body":"entire letter, which you do."},{"speaker":"Problem number two","startTime":2034.45,"endTime":2036.043,"body":"It has to be just perfect."},{"speaker":"Problem number two","startTime":2037.15,"endTime":2039.85,"body":"That means if a single letter is changed"},{"speaker":"Problem number two","startTime":2039.85,"endTime":2043.24,"body":"in the original poem, the"},{"speaker":"Problem number two","startTime":2039.85,"endTime":2043.24,"body":"entire hash will be different."},{"speaker":"Problem number two","startTime":2043.24,"endTime":2044.74,"body":"How do you do that?"},{"speaker":"Problem number two","startTime":2044.74,"endTime":2047.56,"body":"Well, the summary should"},{"speaker":"Problem number two","startTime":2044.74,"endTime":2047.56,"body":"have three characteristics."},{"speaker":"Problem number two","startTime":2047.56,"endTime":2049.81,"body":"The hash summary should"},{"speaker":"Problem number two","startTime":2047.56,"endTime":2049.81,"body":"be the same length."},{"speaker":"Problem number two","startTime":2049.81,"endTime":2053.05,"body":"A particular input will always"},{"speaker":"Problem number two","startTime":2049.81,"endTime":2053.05,"body":"result in the same hash,"},{"speaker":"Problem number two","startTime":2053.05,"endTime":2054.76,"body":"and there should be something called"},{"speaker":"Problem number two","startTime":2054.76,"endTime":2056.113,"body":"a no collision property."},{"speaker":"Problem number two","startTime":2057.07,"endTime":2059.793,"body":"But moment I say that"},{"speaker":"Problem number two","startTime":2057.07,"endTime":2059.793,"body":"people say, \"Wait, what?"},{"speaker":"Problem number two","startTime":2059.793,"endTime":2061.3,"body":"What is this hashing?"},{"speaker":"Problem number two","startTime":2061.3,"endTime":2064.06,"body":"It sounds vaguely"},{"speaker":"Problem number two","startTime":2061.3,"endTime":2064.06,"body":"illegal, hash or whatever."},{"speaker":"Problem number two","startTime":2064.06,"endTime":2065.41,"body":"What's going on over here?\""},{"speaker":"Problem number two","startTime":2067.18,"endTime":2070.41,"body":"Let's introduce you to somebody"},{"speaker":"Problem number two","startTime":2067.18,"endTime":2070.41,"body":"called Hans Peter Luhn,"},{"speaker":"Problem number two","startTime":2070.41,"endTime":2072.49,"body":"who in 1954 got a US patent"},{"speaker":"Problem number two","startTime":2072.49,"endTime":2075.04,"body":"on a computer for verifying numbers."},{"speaker":"Problem number two","startTime":2075.04,"endTime":2077.32,"body":"Now, what was this all about?"},{"speaker":"Problem number two","startTime":2077.32,"endTime":2080.5,"body":"We see at that time there were"},{"speaker":"Problem number two","startTime":2077.32,"endTime":2080.5,"body":"a whole bunch of new numbers"},{"speaker":"Problem number two","startTime":2080.5,"endTime":2081.94,"body":"being introduced for everybody."},{"speaker":"Problem number two","startTime":2081.94,"endTime":2084.46,"body":"Credit card numbers,"},{"speaker":"Problem number two","startTime":2081.94,"endTime":2084.46,"body":"social security numbers,"},{"speaker":"Problem number two","startTime":2084.46,"endTime":2085.293,"body":"things like that."},{"speaker":"Problem number two","startTime":2085.293,"endTime":2087.73,"body":"Everybody needed these numbers,"},{"speaker":"Problem number two","startTime":2087.73,"endTime":2090.01,"body":"and so people would"},{"speaker":"Problem number two","startTime":2087.73,"endTime":2090.01,"body":"transcribe these numbers,"},{"speaker":"Problem number two","startTime":2090.01,"endTime":2091.33,"body":"but they were not electronic."},{"speaker":"Problem number two","startTime":2091.33,"endTime":2094.06,"body":"If you make a mistake in"},{"speaker":"Problem number two","startTime":2091.33,"endTime":2094.06,"body":"writing down the number,"},{"speaker":"Problem number two","startTime":2094.06,"endTime":2097.24,"body":"maybe you attribute the"},{"speaker":"Problem number two","startTime":2094.06,"endTime":2097.24,"body":"debt to the wrong person."},{"speaker":"Problem number two","startTime":2097.24,"endTime":2099.97,"body":"Someone the wrong credit card number."},{"speaker":"Problem number two","startTime":2099.97,"endTime":2102.22,"body":"You need a way to make sure"},{"speaker":"Problem number two","startTime":2099.97,"endTime":2102.22,"body":"that the credit card number"},{"speaker":"Problem number two","startTime":2102.22,"endTime":2104.53,"body":"is in fact a valid credit card number."},{"speaker":"Problem number two","startTime":2104.53,"endTime":2106.093,"body":"How do you do that?"},{"speaker":"Problem number two","startTime":2107.53,"endTime":2109.3,"body":"Luhn came up with an algorithm,"},{"speaker":"Problem number two","startTime":2109.3,"endTime":2110.98,"body":"and the algorithm worked like this."},{"speaker":"Problem number two","startTime":2110.98,"endTime":2112.57,"body":"You start with a 10 digit number,"},{"speaker":"Problem number two","startTime":2112.57,"endTime":2114.1,"body":"and then you go through these steps."},{"speaker":"Problem number two","startTime":2114.1,"endTime":2115.69,"body":"I'll go through these steps with you,"},{"speaker":"Problem number two","startTime":2115.69,"endTime":2118.03,"body":"but once you have this,"},{"speaker":"Problem number two","startTime":2118.03,"endTime":2120.58,"body":"you'll have a check number"},{"speaker":"Problem number two","startTime":2118.03,"endTime":2120.58,"body":"at the end and a check number"},{"speaker":"Problem number two","startTime":2120.58,"endTime":2124.783,"body":"is a summary of the"},{"speaker":"Problem number two","startTime":2120.58,"endTime":2124.783,"body":"entire credit card number."},{"speaker":"Problem number two","startTime":2125.65,"endTime":2127.81,"body":"In later version, the"},{"speaker":"Problem number two","startTime":2125.65,"endTime":2127.81,"body":"check was just appended"},{"speaker":"Problem number two","startTime":2127.81,"endTime":2130.69,"body":"to the original number"},{"speaker":"Problem number two","startTime":2127.81,"endTime":2130.69,"body":"as an extra check digit."},{"speaker":"Problem number two","startTime":2130.69,"endTime":2132.16,"body":"I'll give you an example in a minute."},{"speaker":"Problem number two","startTime":2132.16,"endTime":2134.47,"body":"But even today, if you take your phones"},{"speaker":"Problem number two","startTime":2134.47,"endTime":2137.353,"body":"and you have your IMEI"},{"speaker":"Problem number two","startTime":2134.47,"endTime":2137.353,"body":"number on your phones,"},{"speaker":"Problem number two","startTime":2138.692,"endTime":2141.553,"body":"they use Hans Peter Luhn's algorithm."},{"speaker":"Problem number two","startTime":2142.87,"endTime":2145.66,"body":"Let's start with taking your credit card."},{"speaker":"Problem number two","startTime":2145.66,"endTime":2148.123,"body":"Here is a credit card"},{"speaker":"Problem number two","startTime":2145.66,"endTime":2148.123,"body":"number. Is this valid?"},{"speaker":"Problem number two","startTime":2149.83,"endTime":2151.84,"body":"Once you look at it, you can"},{"speaker":"Problem number two","startTime":2149.83,"endTime":2151.84,"body":"see something right away."},{"speaker":"Problem number two","startTime":2151.84,"endTime":2153.49,"body":"It starts with three, it's 15 digits,"},{"speaker":"Problem number two","startTime":2153.49,"endTime":2155.11,"body":"that means an American Express."},{"speaker":"Problem number two","startTime":2155.11,"endTime":2156.76,"body":"starts with a four, it's Visa,"},{"speaker":"Problem number two","startTime":2156.76,"endTime":2159.58,"body":"starts with a five is"},{"speaker":"Problem number two","startTime":2156.76,"endTime":2159.58,"body":"MasterCard, and so on."},{"speaker":"Problem number two","startTime":2159.58,"endTime":2161.38,"body":"You can immediately figure out"},{"speaker":"Problem number two","startTime":2161.38,"endTime":2163.09,"body":"what that credit card number is,"},{"speaker":"Problem number two","startTime":2163.09,"endTime":2165.37,"body":"but this is an American Express number."},{"speaker":"Problem number two","startTime":2165.37,"endTime":2167.44,"body":"How do we know whether it's valid or not?"},{"speaker":"Problem number two","startTime":2167.44,"endTime":2170.59,"body":"Well, we are going to start"},{"speaker":"Problem number two","startTime":2167.44,"endTime":2170.59,"body":"taking the last digit, six."},{"speaker":"Problem number two","startTime":2170.59,"endTime":2173.56,"body":"That's our check digit, so take it out."},{"speaker":"Problem number two","startTime":2173.56,"endTime":2176.68,"body":"The remaining digits are these numbers."},{"speaker":"Problem number two","startTime":2176.68,"endTime":2179.95,"body":"What I'm going to do is"},{"speaker":"Problem number two","startTime":2176.68,"endTime":2179.95,"body":"double every alternate digit,"},{"speaker":"Problem number two","startTime":2179.95,"endTime":2181.543,"body":"starting at the right."},{"speaker":"Problem number two","startTime":2183.04,"endTime":2186.61,"body":"For example, one becomes"},{"speaker":"Problem number two","startTime":2183.04,"endTime":2186.61,"body":"two, nine stays as nine,"},{"speaker":"Problem number two","startTime":2186.61,"endTime":2188.95,"body":"two becomes four, zero stays as zero,"},{"speaker":"Problem number two","startTime":2188.95,"endTime":2193.39,"body":"one becomes two, two"},{"speaker":"Problem number two","startTime":2188.95,"endTime":2193.39,"body":"stays as two, and so on."},{"speaker":"Problem number two","startTime":2193.39,"endTime":2194.95,"body":"You got the entire contact."},{"speaker":"Problem number two","startTime":2194.95,"endTime":2199.42,"body":"All I'm doing is every"},{"speaker":"Problem number two","startTime":2194.95,"endTime":2199.42,"body":"alternate number I double."},{"speaker":"Problem number two","startTime":2199.42,"endTime":2202.45,"body":"So, I have the sequence"},{"speaker":"Problem number two","startTime":2199.42,"endTime":2202.45,"body":"of numbers over here."},{"speaker":"Problem number two","startTime":2202.45,"endTime":2204.16,"body":"Now, in this sequence of numbers,"},{"speaker":"Problem number two","startTime":2204.16,"endTime":2207.25,"body":"all the double digits I add up."},{"speaker":"Problem number two","startTime":2207.25,"endTime":2211.54,"body":"12 becomes three, 18 becomes"},{"speaker":"Problem number two","startTime":2207.25,"endTime":2211.54,"body":"nine, 18 becomes nine."},{"speaker":"Problem number two","startTime":2211.54,"endTime":2215.44,"body":"Then I add all the digits"},{"speaker":"Problem number two","startTime":2211.54,"endTime":2215.44,"body":"together, I get 64,"},{"speaker":"Problem number two","startTime":2215.44,"endTime":2217.6,"body":"multiply that by nine,"},{"speaker":"Problem number two","startTime":2217.6,"endTime":2220.42,"body":"and look at the last digit of the product."},{"speaker":"Problem number two","startTime":2220.42,"endTime":2222.16,"body":"Is the last digit the product the same"},{"speaker":"Problem number two","startTime":2222.16,"endTime":2223.54,"body":"as the last digit of the original?"},{"speaker":"Problem number two","startTime":2223.54,"endTime":2226.06,"body":"If it is, that's a valid"},{"speaker":"Problem number two","startTime":2223.54,"endTime":2226.06,"body":"credit card number."},{"speaker":"Problem number two","startTime":2226.06,"endTime":2227.44,"body":"I don't need to go on the internet,"},{"speaker":"Problem number two","startTime":2227.44,"endTime":2230.29,"body":"I don't need to check"},{"speaker":"Problem number two","startTime":2227.44,"endTime":2230.29,"body":"anything. I run the algorithm."},{"speaker":"Problem number two","startTime":2230.29,"endTime":2232.81,"body":"The last digit is immediately a summary"},{"speaker":"Problem number two","startTime":2232.81,"endTime":2235.24,"body":"of everything in that number."},{"speaker":"Problem number two","startTime":2235.24,"endTime":2238.66,"body":"If this last digit is anything but six,"},{"speaker":"Problem number two","startTime":2238.66,"endTime":2240.96,"body":"I know this is not a"},{"speaker":"Problem number two","startTime":2238.66,"endTime":2240.96,"body":"valid credit card number."},{"speaker":"Problem number two","startTime":2242.26,"endTime":2247.26,"body":"That's the idea of hashing."},{"speaker":"Problem number two","startTime":2242.26,"endTime":2247.26,"body":"Let's take a word, \"Adam.\""},{"speaker":"Problem number two","startTime":2247.96,"endTime":2249.61,"body":"And I'm going to give"},{"speaker":"Problem number two","startTime":2247.96,"endTime":2249.61,"body":"a number to every word."},{"speaker":"Problem number two","startTime":2249.61,"endTime":2252.94,"body":"So, Adam becomes A is"},{"speaker":"Problem number two","startTime":2249.61,"endTime":2252.94,"body":"one, B is two, and so on."},{"speaker":"Problem number two","startTime":2252.94,"endTime":2255.4,"body":"Of course, capital A will"},{"speaker":"Problem number two","startTime":2252.94,"endTime":2255.4,"body":"have a different value"},{"speaker":"Problem number two","startTime":2255.4,"endTime":2256.48,"body":"from small A."},{"speaker":"Problem number two","startTime":2256.48,"endTime":2259.96,"body":"One will have a value,"},{"speaker":"Problem number two","startTime":2256.48,"endTime":2259.96,"body":"the commas, the periods,"},{"speaker":"Problem number two","startTime":2259.96,"endTime":2261.82,"body":"all of them will have different values."},{"speaker":"Problem number two","startTime":2261.82,"endTime":2263.26,"body":"But let's make it easy."},{"speaker":"Problem number two","startTime":2263.26,"endTime":2265.21,"body":"Let's just say small letters in our text,"},{"speaker":"Problem number two","startTime":2265.21,"endTime":2270.21,"body":"Adam becomes one, four, one, 13. A-D-A-M."},{"speaker":"Problem number two","startTime":2270.28,"endTime":2274.78,"body":"Now, I'm also going to fix a"},{"speaker":"Problem number two","startTime":2270.28,"endTime":2274.78,"body":"fixed length for the summary."},{"speaker":"Problem number two","startTime":2274.78,"endTime":2275.863,"body":"Let's say this is 10."},{"speaker":"Problem number two","startTime":2277.18,"endTime":2281.957,"body":"Adam takes four digits. A1, 4, 1, 13."},{"speaker":"Problem number two","startTime":2283.12,"endTime":2283.99,"body":"What do I do?"},{"speaker":"Problem number two","startTime":2283.99,"endTime":2287.44,"body":"I tell the person reading it,"},{"speaker":"Problem number two","startTime":2283.99,"endTime":2287.44,"body":"\"This is stopping at four,"},{"speaker":"Problem number two","startTime":2287.44,"endTime":2289.57,"body":"so add a one to stop it.\""},{"speaker":"Problem number two","startTime":2289.57,"endTime":2290.817,"body":"Then I pad it out with zeros,"},{"speaker":"Problem number two","startTime":2290.817,"endTime":2294.22,"body":"and at the end I add the"},{"speaker":"Problem number two","startTime":2290.817,"endTime":2294.22,"body":"number of original digits"},{"speaker":"Problem number two","startTime":2294.22,"endTime":2295.053,"body":"to look for."},{"speaker":"Problem number two","startTime":2295.053,"endTime":2296.417,"body":"Somebody looking at this will say,"},{"speaker":"Problem number two","startTime":2296.417,"endTime":2299.02,"body":"\"Okay, I'm looking for the first four,"},{"speaker":"Problem number two","startTime":2299.02,"endTime":2300.34,"body":"and I know it stops right here."},{"speaker":"Problem number two","startTime":2300.34,"endTime":2302.98,"body":"So, this is my original"},{"speaker":"Problem number two","startTime":2300.34,"endTime":2302.98,"body":"word I'm looking for.\""},{"speaker":"Problem number two","startTime":2302.98,"endTime":2305.53,"body":"This is the hash. 10 digits."},{"speaker":"Problem number two","startTime":2305.53,"endTime":2307.81,"body":"And every hash will have the same thing."},{"speaker":"Problem number two","startTime":2307.81,"endTime":2310.3,"body":"If you have something that's"},{"speaker":"Problem number two","startTime":2307.81,"endTime":2310.3,"body":"longer than four digits,"},{"speaker":"Problem number two","startTime":2310.3,"endTime":2312.4,"body":"longer than 10, just chop it up."},{"speaker":"Problem number two","startTime":2312.4,"endTime":2315.58,"body":"And then, eventually you get to something"},{"speaker":"Problem number two","startTime":2315.58,"endTime":2317.683,"body":"which is always just 10 digits."},{"speaker":"Problem number two","startTime":2318.7,"endTime":2320.56,"body":"Let's take an example."},{"speaker":"Problem number two","startTime":2320.56,"endTime":2322.06,"body":"I'm going to show you something"},{"speaker":"Problem number two","startTime":2322.06,"endTime":2323.983,"body":"called the SHA algorithm."},{"speaker":"Problem number two","startTime":2325.09,"endTime":2327.583,"body":"So, this is a typical hash calculator."},{"speaker":"Problem number two","startTime":2330.01,"endTime":2331.78,"body":"You can type in anything here."},{"speaker":"Problem number two","startTime":2331.78,"endTime":2334.807,"body":"For example, \"This is a test.\""},{"speaker":"Problem number two","startTime":2335.8,"endTime":2337.933,"body":"And you ask it to generate the hash."},{"speaker":"Problem number two","startTime":2339.52,"endTime":2341.29,"body":"That's the hash it generates."},{"speaker":"Problem number two","startTime":2341.29,"endTime":2345.55,"body":"Notice that the hash size"},{"speaker":"Problem number two","startTime":2341.29,"endTime":2345.55,"body":"will always stay the same,"},{"speaker":"Problem number two","startTime":2345.55,"endTime":2347.65,"body":"and if you change even a little bit,"},{"speaker":"Problem number two","startTime":2347.65,"endTime":2349.453,"body":"let me add a full stop over here,"},{"speaker":"Problem number two","startTime":2350.98,"endTime":2353.173,"body":"the hash becomes completely different."},{"speaker":"Problem number two","startTime":2354.37,"endTime":2357.37,"body":"Every hash will be"},{"speaker":"Problem number two","startTime":2354.37,"endTime":2357.37,"body":"identical for the same one."},{"speaker":"Problem number two","startTime":2357.37,"endTime":2360.193,"body":"If I get rid of the dot, I go back in,"},{"speaker":"Problem number two","startTime":2361.96,"endTime":2364.03,"body":"That's the original hash I just saw."},{"speaker":"Problem number two","startTime":2364.03,"endTime":2368.323,"body":"Add a full stop, that's the"},{"speaker":"Problem number two","startTime":2364.03,"endTime":2368.323,"body":"second hash we just saw."},{"speaker":"Problem number two","startTime":2370.42,"endTime":2374.2,"body":"Every one is a hash summary"},{"speaker":"Problem number two","startTime":2370.42,"endTime":2374.2,"body":"of your original text,"},{"speaker":"Problem number two","startTime":2374.2,"endTime":2377.65,"body":"and you can do this with any"},{"speaker":"Problem number two","startTime":2374.2,"endTime":2377.65,"body":"length of texts you want."},{"speaker":"Problem number two","startTime":2377.65,"endTime":2380.47,"body":"You can have a simple thing,"},{"speaker":"Problem number two","startTime":2377.65,"endTime":2380.47,"body":"you can write a letter,"},{"speaker":"Problem number two","startTime":2380.47,"endTime":2381.913,"body":"you can say."},{"speaker":"Problem number two","startTime":2410.05,"endTime":2414.4,"body":"- [Professor Rao] Simple letter,"},{"speaker":"Problem number two","startTime":2410.05,"endTime":2414.4,"body":"hit the hash, same length."},{"speaker":"Problem number two","startTime":2414.4,"endTime":2416.35,"body":"It's a completely"},{"speaker":"Problem number two","startTime":2414.4,"endTime":2416.35,"body":"different hash over here."},{"speaker":"Problem number two","startTime":2416.35,"endTime":2417.55,"body":"If I change even a little bit,"},{"speaker":"Problem number two","startTime":2417.55,"endTime":2420.073,"body":"maybe I make a little"},{"speaker":"Problem number two","startTime":2417.55,"endTime":2420.073,"body":"spelling mistake over here,"},{"speaker":"Problem number two","startTime":2422.41,"endTime":2423.243,"body":"no problem."},{"speaker":"Problem number two","startTime":2423.243,"endTime":2424.076,"body":"Hash is completely different."},{"speaker":"Problem number two","startTime":2424.076,"endTime":2426.01,"body":"Literally, all I have to"},{"speaker":"Problem number two","startTime":2424.076,"endTime":2426.01,"body":"do is give you the hash."},{"speaker":"Problem number two","startTime":2426.01,"endTime":2428.77,"body":"I know that if the hash doesn't match,"},{"speaker":"Problem number two","startTime":2428.77,"endTime":2430.03,"body":"I know that something has changed."},{"speaker":"Problem number two","startTime":2430.03,"endTime":2431.35,"body":"I don't know what has changed,"},{"speaker":"Problem number two","startTime":2431.35,"endTime":2432.97,"body":"because I just got the summary,"},{"speaker":"Problem number two","startTime":2432.97,"endTime":2434.953,"body":"but I know that something is different."},{"speaker":"Problem number two","startTime":2435.97,"endTime":2437.953,"body":"That's the purpose of a hash."},{"speaker":"Problem number two","startTime":2439.51,"endTime":2442.18,"body":"Now, how do I bring this all together?"},{"speaker":"Problem number two","startTime":2442.18,"endTime":2444.52,"body":"I also need to be sure the last problem"},{"speaker":"Problem number two","startTime":2444.52,"endTime":2447.13,"body":"that Romeo is not writing the same letter"},{"speaker":"Problem number two","startTime":2447.13,"endTime":2449.08,"body":"to five other girls."},{"speaker":"Problem number two","startTime":2449.08,"endTime":2451.48,"body":"I'm getting the hash, I'll"},{"speaker":"Problem number two","startTime":2449.08,"endTime":2451.48,"body":"put the hash in a minute."},{"speaker":"Problem number two","startTime":2451.48,"endTime":2453.52,"body":"But the hash is a way of constructing"},{"speaker":"Problem number two","startTime":2453.52,"endTime":2457.9,"body":"any length I want to get a"},{"speaker":"Problem number two","startTime":2453.52,"endTime":2457.9,"body":"same summary for that field."},{"speaker":"Problem number two","startTime":2457.9,"endTime":2458.983,"body":"This is the last bit."},{"speaker":"Problem number two","startTime":2460.72,"endTime":2465.72,"body":"Let me introduce you to"},{"speaker":"Problem number two","startTime":2460.72,"endTime":2465.72,"body":"Yap Island in Micronesia"},{"speaker":"Problem number two","startTime":2467.41,"endTime":2468.253,"body":"in the Pacific."},{"speaker":"Problem number two","startTime":2469.27,"endTime":2473.68,"body":"This is an island near Palau"},{"speaker":"Problem number two","startTime":2469.27,"endTime":2473.68,"body":"and Guam, all these areas,"},{"speaker":"Problem number two","startTime":2473.68,"endTime":2475.81,"body":"pretty remote part of the Pacific,"},{"speaker":"Problem number two","startTime":2475.81,"endTime":2479.59,"body":"where the Islanders some 1500 years ago"},{"speaker":"Problem number two","startTime":2479.59,"endTime":2484.59,"body":"had the idea of going 300"},{"speaker":"Problem number two","startTime":2479.59,"endTime":2484.59,"body":"miles across the open ocean."},{"speaker":"Problem number two","startTime":2484.69,"endTime":2489.69,"body":"By the way, the English"},{"speaker":"Problem number two","startTime":2484.69,"endTime":2489.69,"body":"Channel, at its narrowest,"},{"speaker":"Problem number two","startTime":2490.24,"endTime":2491.89,"body":"is about 21 miles."},{"speaker":"Problem number two","startTime":2491.89,"endTime":2494.17,"body":"This is something like 15 times the width"},{"speaker":"Problem number two","startTime":2494.17,"endTime":2498.37,"body":"of the English Channel in the open ocean,"},{"speaker":"Problem number two","startTime":2498.37,"endTime":2502.42,"body":"to go to a different island"},{"speaker":"Problem number two","startTime":2498.37,"endTime":2502.42,"body":"to carve pieces of stone"},{"speaker":"Problem number two","startTime":2502.42,"endTime":2504.25,"body":"and use that as money."},{"speaker":"Problem number two","startTime":2504.25,"endTime":2506.203,"body":"How big are these pieces of stone?"},{"speaker":"Problem number two","startTime":2507.85,"endTime":2508.683,"body":"Pretty big."},{"speaker":"Problem number two","startTime":2509.53,"endTime":2512.86,"body":"The size. This is a stone"},{"speaker":"Problem number two","startTime":2509.53,"endTime":2512.86,"body":"which weighs several tons."},{"speaker":"Problem number two","startTime":2512.86,"endTime":2517.39,"body":"It's impossible to move."},{"speaker":"Problem number two","startTime":2512.86,"endTime":2517.39,"body":"So, why did this happen?"},{"speaker":"Problem number two","startTime":2517.39,"endTime":2520.21,"body":"Why are these guys using this as money?"},{"speaker":"Problem number two","startTime":2520.21,"endTime":2522.04,"body":"Turns out, there's a story."},{"speaker":"Problem number two","startTime":2522.04,"endTime":2523.78,"body":"There are lots of stories."},{"speaker":"Problem number two","startTime":2522.04,"endTime":2523.78,"body":"This goes back 1500."},{"speaker":"Problem number two","startTime":2523.78,"endTime":2525.64,"body":"We don't really know why it happened,"},{"speaker":"Problem number two","startTime":2525.64,"endTime":2529.42,"body":"But the story is that in the Yap Islands,"},{"speaker":"Problem number two","startTime":2529.42,"endTime":2533.47,"body":"these guys went fishing,"},{"speaker":"Problem number two","startTime":2529.42,"endTime":2533.47,"body":"they were blown off course."},{"speaker":"Problem number two","startTime":2533.47,"endTime":2535.363,"body":"They landed on this remote island."},{"speaker":"Problem number two","startTime":2536.62,"endTime":2540.07,"body":"Their stock of fish all destroyed."},{"speaker":"Problem number two","startTime":2540.07,"endTime":2542.56,"body":"They carved a stone out"},{"speaker":"Problem number two","startTime":2540.07,"endTime":2542.56,"body":"of this calciferous stone"},{"speaker":"Problem number two","startTime":2542.56,"endTime":2545.027,"body":"over there and they brought"},{"speaker":"Problem number two","startTime":2542.56,"endTime":2545.027,"body":"it back to show their king."},{"speaker":"Problem number two","startTime":2545.027,"endTime":2546.43,"body":"\"Oh look, here's our tribute."},{"speaker":"Problem number two","startTime":2546.43,"endTime":2548.71,"body":"This is the size of the"},{"speaker":"Problem number two","startTime":2546.43,"endTime":2548.71,"body":"fish we would've caught,"},{"speaker":"Problem number two","startTime":2548.71,"endTime":2550.12,"body":"had we caught fish.\""},{"speaker":"Problem number two","startTime":2550.12,"endTime":2552.37,"body":"I mean, if I was a king, I'd"},{"speaker":"Problem number two","startTime":2550.12,"endTime":2552.37,"body":"be somewhat disappointed."},{"speaker":"Problem number two","startTime":2552.37,"endTime":2556.48,"body":"But anyway, the point was that"},{"speaker":"Problem number two","startTime":2552.37,"endTime":2556.48,"body":"that became used as currency."},{"speaker":"Problem number two","startTime":2556.48,"endTime":2561.1,"body":"It became standardized and then"},{"speaker":"Problem number two","startTime":2556.48,"endTime":2561.1,"body":"they started having stones."},{"speaker":"Problem number two","startTime":2561.1,"endTime":2562.54,"body":"How do the stones work?"},{"speaker":"Problem number two","startTime":2562.54,"endTime":2564.303,"body":"Well, you go to this"},{"speaker":"Problem number two","startTime":2562.54,"endTime":2564.303,"body":"island 300 miles away,"},{"speaker":"Problem number two","startTime":2564.303,"endTime":2566.47,"body":"you cut the stone and you bring it back,"},{"speaker":"Problem number two","startTime":2566.47,"endTime":2571.36,"body":"and then you put it outside"},{"speaker":"Problem number two","startTime":2566.47,"endTime":2571.36,"body":"your house like this."},{"speaker":"Problem number two","startTime":2571.36,"endTime":2576.1,"body":"Now, this value of the"},{"speaker":"Problem number two","startTime":2571.36,"endTime":2576.1,"body":"stone depends on the story."},{"speaker":"Problem number two","startTime":2576.1,"endTime":2578.47,"body":"It doesn't just depend"},{"speaker":"Problem number two","startTime":2576.1,"endTime":2578.47,"body":"on the size of the stone."},{"speaker":"Problem number two","startTime":2578.47,"endTime":2581.64,"body":"For example, it could be"},{"speaker":"Problem number two","startTime":2578.47,"endTime":2581.64,"body":"that it's commissioned"},{"speaker":"Problem number two","startTime":2581.64,"endTime":2584.41,"body":"by a famous explorer, increases"},{"speaker":"Problem number two","startTime":2581.64,"endTime":2584.41,"body":"the value of the stone."},{"speaker":"Problem number two","startTime":2584.41,"endTime":2586.48,"body":"Several people died in the ocean"},{"speaker":"Problem number two","startTime":2586.48,"endTime":2588.16,"body":"while they're trying to"},{"speaker":"Problem number two","startTime":2586.48,"endTime":2588.16,"body":"bring the stone back,"},{"speaker":"Problem number two","startTime":2588.16,"endTime":2590.05,"body":"increases the value of the stone."},{"speaker":"Problem number two","startTime":2590.05,"endTime":2592.84,"body":"Carved using modern techniques"},{"speaker":"Problem number two","startTime":2590.05,"endTime":2592.84,"body":"to make it look smooth,"},{"speaker":"Problem number two","startTime":2592.84,"endTime":2594.13,"body":"decreases the value of the stone,"},{"speaker":"Problem number two","startTime":2594.13,"endTime":2597.07,"body":"because the amount of effort"},{"speaker":"Problem number two","startTime":2594.13,"endTime":2597.07,"body":"going to carving the stone"},{"speaker":"Problem number two","startTime":2597.07,"endTime":2598.21,"body":"is lower."},{"speaker":"Problem number two","startTime":2598.21,"endTime":2599.8,"body":"The stone can also earn interest."},{"speaker":"Problem number two","startTime":2599.8,"endTime":2603.73,"body":"For example, if you keep"},{"speaker":"Problem number two","startTime":2599.8,"endTime":2603.73,"body":"the stone outside your house"},{"speaker":"Problem number two","startTime":2603.73,"endTime":2606.16,"body":"and your daughter later"},{"speaker":"Problem number two","startTime":2603.73,"endTime":2606.16,"body":"gets married to somebody"},{"speaker":"Problem number two","startTime":2606.16,"endTime":2609.91,"body":"and has five children who"},{"speaker":"Problem number two","startTime":2606.16,"endTime":2609.91,"body":"contribute a lot to the society,"},{"speaker":"Problem number two","startTime":2609.91,"endTime":2611.89,"body":"the value of the stone goes up."},{"speaker":"Problem number two","startTime":2611.89,"endTime":2614.83,"body":"But more important, you can"},{"speaker":"Problem number two","startTime":2611.89,"endTime":2614.83,"body":"use the stone as currency."},{"speaker":"Problem number two","startTime":2614.83,"endTime":2617.86,"body":"That means, suppose I want"},{"speaker":"Problem number two","startTime":2614.83,"endTime":2617.86,"body":"to buy a fishing ground."},{"speaker":"Problem number two","startTime":2617.86,"endTime":2619.36,"body":"By the way, there are"},{"speaker":"Problem number two","startTime":2617.86,"endTime":2619.36,"body":"other measures of things."},{"speaker":"Problem number two","startTime":2619.36,"endTime":2621.01,"body":"You just don't use the Yap stones."},{"speaker":"Problem number two","startTime":2621.01,"endTime":2624.19,"body":"They also use cloud shells,"},{"speaker":"Problem number two","startTime":2621.01,"endTime":2624.19,"body":"they also used beads."},{"speaker":"Problem number two","startTime":2624.19,"endTime":2625.54,"body":"They use a whole bunch of other things."},{"speaker":"Problem number two","startTime":2625.54,"endTime":2627.31,"body":"And today, if you go to Yap Island,"},{"speaker":"Problem number two","startTime":2627.31,"endTime":2631.27,"body":"they also take US dollars,"},{"speaker":"Problem number two","startTime":2627.31,"endTime":2631.27,"body":"British pounds, and euros."},{"speaker":"Problem number two","startTime":2631.27,"endTime":2633.94,"body":"This is not the only"},{"speaker":"Problem number two","startTime":2631.27,"endTime":2633.94,"body":"currency they use there,"},{"speaker":"Problem number two","startTime":2633.94,"endTime":2636.22,"body":"but it's an example of a blockchain."},{"speaker":"Problem number two","startTime":2636.22,"endTime":2637.51,"body":"Why?"},{"speaker":"Problem number two","startTime":2637.51,"endTime":2639.13,"body":"Suppose you have this outside your house,"},{"speaker":"Problem number two","startTime":2639.13,"endTime":2641.11,"body":"and you want to buy a fishing ground."},{"speaker":"Problem number two","startTime":2641.11,"endTime":2642.55,"body":"You don't move the stone,"},{"speaker":"Problem number two","startTime":2642.55,"endTime":2645.94,"body":"you give possession of the"},{"speaker":"Problem number two","startTime":2642.55,"endTime":2645.94,"body":"stone to somebody else."},{"speaker":"Problem number two","startTime":2645.94,"endTime":2647.59,"body":"That person now has the stone,"},{"speaker":"Problem number two","startTime":2647.59,"endTime":2650.02,"body":"even though it's outside your house."},{"speaker":"Problem number two","startTime":2650.02,"endTime":2652.15,"body":"There's a limited number"},{"speaker":"Problem number two","startTime":2650.02,"endTime":2652.15,"body":"of tribes in the island."},{"speaker":"Problem number two","startTime":2652.15,"endTime":2656.56,"body":"Everybody can trace the"},{"speaker":"Problem number two","startTime":2652.15,"endTime":2656.56,"body":"entire history of the stones"},{"speaker":"Problem number two","startTime":2656.56,"endTime":2658.33,"body":"back to the origin."},{"speaker":"Problem number two","startTime":2658.33,"endTime":2659.35,"body":"That means, in other words,"},{"speaker":"Problem number two","startTime":2659.35,"endTime":2661.45,"body":"we know from the time the stone was cut,"},{"speaker":"Problem number two","startTime":2661.45,"endTime":2663.94,"body":"who owned the stone and who"},{"speaker":"Problem number two","startTime":2661.45,"endTime":2663.94,"body":"has possession of the stone"},{"speaker":"Problem number two","startTime":2663.94,"endTime":2665.98,"body":"at any one point in time."},{"speaker":"Problem number two","startTime":2665.98,"endTime":2668.47,"body":"That's the idea of a blockchain as well."},{"speaker":"Problem number two","startTime":2668.47,"endTime":2671.56,"body":"That means even you buy"},{"speaker":"Problem number two","startTime":2668.47,"endTime":2671.56,"body":"something on the blockchain,"},{"speaker":"Problem number two","startTime":2671.56,"endTime":2673.78,"body":"you have to prove where"},{"speaker":"Problem number two","startTime":2671.56,"endTime":2673.78,"body":"the money came from."},{"speaker":"Problem number two","startTime":2673.78,"endTime":2676.96,"body":"You can't just say, \"Okay,"},{"speaker":"Problem number two","startTime":2673.78,"endTime":2676.96,"body":"I have five Bitcoin.\""},{"speaker":"Problem number two","startTime":2676.96,"endTime":2679.0,"body":"Where did you get the five Bitcoin from?"},{"speaker":"Problem number two","startTime":2679.0,"endTime":2681.73,"body":"Somebody should be able to"},{"speaker":"Problem number two","startTime":2679.0,"endTime":2681.73,"body":"trace the entire history"},{"speaker":"Problem number two","startTime":2681.73,"endTime":2685.0,"body":"of Bitcoin all the way back"},{"speaker":"Problem number two","startTime":2681.73,"endTime":2685.0,"body":"from the genesis block."},{"speaker":"Problem number two","startTime":2685.0,"endTime":2688.87,"body":"You can download the entire"},{"speaker":"Problem number two","startTime":2685.0,"endTime":2688.87,"body":"blockchain onto USB stick,"},{"speaker":"Problem number two","startTime":2688.87,"endTime":2691.48,"body":"and then you can trace the history"},{"speaker":"Problem number two","startTime":2691.48,"endTime":2695.41,"body":"of every Bitcoin ever"},{"speaker":"Problem number two","startTime":2691.48,"endTime":2695.41,"body":"created on that system."},{"speaker":"Problem number two","startTime":2695.41,"endTime":2696.55,"body":"You can't double spend,"},{"speaker":"Problem number two","startTime":2696.55,"endTime":2698.53,"body":"because somebody will go in"},{"speaker":"Problem number two","startTime":2696.55,"endTime":2698.53,"body":"there and say, \"Wait a minute,"},{"speaker":"Problem number two","startTime":2698.53,"endTime":2700.12,"body":"you say you're spending five Bitcoin."},{"speaker":"Problem number two","startTime":2700.12,"endTime":2701.23,"body":"Where did the money come from?"},{"speaker":"Problem number two","startTime":2701.23,"endTime":2703.18,"body":"I can't see it anywhere"},{"speaker":"Problem number two","startTime":2701.23,"endTime":2703.18,"body":"in the blockchain.\""},{"speaker":"Problem number two","startTime":2703.18,"endTime":2704.53,"body":"Has to come from somewhere."},{"speaker":"Problem number two","startTime":2705.37,"endTime":2708.55,"body":"That allows us to prevent double spending."},{"speaker":"Problem number two","startTime":2708.55,"endTime":2710.89,"body":"In a way, it's like"},{"speaker":"Problem number two","startTime":2708.55,"endTime":2710.89,"body":"saying in Romeo's case,"},{"speaker":"Problem number two","startTime":2710.89,"endTime":2713.683,"body":"every letter Romeo's ever"},{"speaker":"Problem number two","startTime":2710.89,"endTime":2713.683,"body":"written is on the blockchain."},{"speaker":"Problem number two","startTime":2715.06,"endTime":2716.567,"body":"Juliet can go down a list and say,"},{"speaker":"Problem number two","startTime":2716.567,"endTime":2719.68,"body":"\"Hmm, I'm sorry, you are"},{"speaker":"Problem number two","startTime":2716.567,"endTime":2719.68,"body":"writing the same letter."},{"speaker":"Problem number two","startTime":2719.68,"endTime":2722.11,"body":"I've seen that letter five"},{"speaker":"Problem number two","startTime":2719.68,"endTime":2722.11,"body":"times in the blockchain."},{"speaker":"Problem number two","startTime":2722.11,"endTime":2724.61,"body":"So, you can't write five"},{"speaker":"Problem number two","startTime":2722.11,"endTime":2724.61,"body":"letters to other people.\""},{"speaker":"Problem number two","startTime":2727.18,"endTime":2729.52,"body":"But who verifies the transaction?"},{"speaker":"Problem number two","startTime":2729.52,"endTime":2731.95,"body":"The answer is people call them miners."},{"speaker":"Problem number two","startTime":2731.95,"endTime":2733.72,"body":"What do the miners do?"},{"speaker":"Problem number two","startTime":2733.72,"endTime":2738.49,"body":"Their job is to create a"},{"speaker":"Problem number two","startTime":2733.72,"endTime":2738.49,"body":"solution which is allowed"},{"speaker":"Problem number two","startTime":2738.49,"endTime":2739.81,"body":"by the system."},{"speaker":"Problem number two","startTime":2739.81,"endTime":2740.98,"body":"What does that mean?"},{"speaker":"Problem number two","startTime":2740.98,"endTime":2743.8,"body":"Let's say one particular"},{"speaker":"Problem number two","startTime":2740.98,"endTime":2743.8,"body":"solution is you must have"},{"speaker":"Problem number two","startTime":2743.8,"endTime":2747.463,"body":"three leading zeros in the"},{"speaker":"Problem number two","startTime":2743.8,"endTime":2747.463,"body":"solution, which is a hash."},{"speaker":"Problem number two","startTime":2748.63,"endTime":2751.09,"body":"We try to hash a set of transactions"},{"speaker":"Problem number two","startTime":2751.09,"endTime":2752.653,"body":"which will fit this pattern."},{"speaker":"Problem number two","startTime":2753.52,"endTime":2754.84,"body":"What does that mean?"},{"speaker":"Problem number two","startTime":2754.84,"endTime":2757.667,"body":"Let's look at a set of"},{"speaker":"Problem number two","startTime":2754.84,"endTime":2757.667,"body":"transactions like this."},{"speaker":"Problem number two","startTime":2757.667,"endTime":2759.97,"body":"\"Alice owes Maya one Bitcoin for a movie.\""},{"speaker":"Problem number two","startTime":2759.97,"endTime":2761.11,"body":"That's an expensive movie,"},{"speaker":"Problem number two","startTime":2761.11,"endTime":2763.483,"body":"because Bitcoin is about $16,000 now."},{"speaker":"Problem number two","startTime":2766.056,"endTime":2766.889,"body":"What do you do?"},{"speaker":"Problem number two","startTime":2767.92,"endTime":2771.67,"body":"What the miner does is"},{"speaker":"Problem number two","startTime":2767.92,"endTime":2771.67,"body":"miner hashes that set"},{"speaker":"Problem number two","startTime":2771.67,"endTime":2774.04,"body":"of transactions, picks"},{"speaker":"Problem number two","startTime":2771.67,"endTime":2774.04,"body":"any set of transactions."},{"speaker":"Problem number two","startTime":2774.04,"endTime":2775.303,"body":"Five, 10, whatever."},{"speaker":"Problem number two","startTime":2775.303,"endTime":2778.96,"body":"They hash that, you got one hash address."},{"speaker":"Problem number two","startTime":2778.96,"endTime":2782.47,"body":"Now, let's take an example."},{"speaker":"Problem number two","startTime":2782.47,"endTime":2785.383,"body":"Let's say this is your hash address."},{"speaker":"Problem number two","startTime":2789.466,"endTime":2793.03,"body":"You have this, you do calculate a hash."},{"speaker":"Problem number two","startTime":2793.03,"endTime":2795.913,"body":"Now notice that hash there, it has 639."},{"speaker":"Problem number two","startTime":2796.93,"endTime":2798.7,"body":"It does not starting with a zero,"},{"speaker":"Problem number two","startTime":2798.7,"endTime":2800.5,"body":"it not doesn't have three leading zeros."},{"speaker":"Problem number two","startTime":2800.5,"endTime":2802.54,"body":"This is not a valid solution."},{"speaker":"Problem number two","startTime":2802.54,"endTime":2806.32,"body":"What do I do? I add a"},{"speaker":"Problem number two","startTime":2802.54,"endTime":2806.32,"body":"trial number to the end."},{"speaker":"Problem number two","startTime":2806.32,"endTime":2809.7,"body":"I say, \"Let's add one,\" I recalculate it,"},{"speaker":"Problem number two","startTime":2809.7,"endTime":2812.14,"body":"it starts with a nine, it doesn't work."},{"speaker":"Problem number two","startTime":2812.14,"endTime":2814.753,"body":"Let's do it again. Let's start with two."},{"speaker":"Problem number two","startTime":2817.45,"endTime":2820.093,"body":"Oh, it starts four. Okay, not good."},{"speaker":"Problem number two","startTime":2821.26,"endTime":2822.79,"body":"Oh, it still starts with a one."},{"speaker":"Problem number two","startTime":2822.79,"endTime":2824.92,"body":"Let's do four."},{"speaker":"Problem number two","startTime":2824.92,"endTime":2826.6,"body":"This is the miner's job."},{"speaker":"Problem number two","startTime":2826.6,"endTime":2830.26,"body":"They keep putting in number"},{"speaker":"Problem number two","startTime":2826.6,"endTime":2830.26,"body":"after number after number"},{"speaker":"Problem number two","startTime":2830.26,"endTime":2832.51,"body":"into this to get a solution"},{"speaker":"Problem number two","startTime":2832.51,"endTime":2834.553,"body":"which starts with three leading zeros."},{"speaker":"Problem number two","startTime":2835.57,"endTime":2838.113,"body":"Anyone feel lucky? Would you"},{"speaker":"Problem number two","startTime":2835.57,"endTime":2838.113,"body":"like to give me a number?"},{"speaker":"Problem number two","startTime":2840.19,"endTime":2841.49,"body":"I have no idea what it is."},{"speaker":"Problem number two","startTime":2842.367,"endTime":2844.517,"body":"- [Audience] Eight."},{"speaker":"Problem number two","startTime":2842.367,"endTime":2844.517,"body":"- Eight, let's try it."},{"speaker":"Problem number two","startTime":2848.95,"endTime":2849.883,"body":"No, I'm sorry."},{"speaker":"Problem number two","startTime":2851.41,"endTime":2853.03,"body":"Literally, that's one of the reasons"},{"speaker":"Problem number two","startTime":2853.03,"endTime":2855.4,"body":"why it's such a difficult job."},{"speaker":"Problem number two","startTime":2855.4,"endTime":2859.03,"body":"The miners spend hours trying"},{"speaker":"Problem number two","startTime":2855.4,"endTime":2859.03,"body":"to solve these problems."},{"speaker":"Problem number two","startTime":2859.03,"endTime":2861.07,"body":"And as you increase the"},{"speaker":"Problem number two","startTime":2859.03,"endTime":2861.07,"body":"number of leading zeros,"},{"speaker":"Problem number two","startTime":2861.07,"endTime":2863.02,"body":"the problem becomes more difficult,"},{"speaker":"Problem number two","startTime":2863.02,"endTime":2865.24,"body":"because you have to run"},{"speaker":"Problem number two","startTime":2863.02,"endTime":2865.24,"body":"through more and more ways"},{"speaker":"Problem number two","startTime":2865.24,"endTime":2867.313,"body":"of trying to get a perfect hash."},{"speaker":"Problem number two","startTime":2868.18,"endTime":2869.38,"body":"So, that's the idea."},{"speaker":"Problem number two","startTime":2869.38,"endTime":2872.56,"body":"Once you have the hash, what happens?"},{"speaker":"Problem number two","startTime":2872.56,"endTime":2876.25,"body":"Well, once you have the"},{"speaker":"Problem number two","startTime":2872.56,"endTime":2876.25,"body":"hash, what do you do?"},{"speaker":"Problem number two","startTime":2876.25,"endTime":2878.05,"body":"You basically broadcast to everybody."},{"speaker":"Problem number two","startTime":2878.05,"endTime":2880.15,"body":"Say, \"I've solved this problem,\""},{"speaker":"Problem number two","startTime":2880.15,"endTime":2884.05,"body":"and you give that number to"},{"speaker":"Problem number two","startTime":2880.15,"endTime":2884.05,"body":"everybody, they take that thing,"},{"speaker":"Problem number two","startTime":2884.05,"endTime":2887.11,"body":"put it into their hash"},{"speaker":"Problem number two","startTime":2884.05,"endTime":2887.11,"body":"algorithm, put that trial number,"},{"speaker":"Problem number two","startTime":2887.11,"endTime":2888.64,"body":"and check whether it has three zeros."},{"speaker":"Problem number two","startTime":2888.64,"endTime":2890.74,"body":"If it does, say, \"Okay, we won,\""},{"speaker":"Problem number two","startTime":2890.74,"endTime":2893.74,"body":"and this guy gets a fees paid by every one"},{"speaker":"Problem number two","startTime":2893.74,"endTime":2896.77,"body":"of this one plus new money"},{"speaker":"Problem number two","startTime":2893.74,"endTime":2896.77,"body":"created by the system,"},{"speaker":"Problem number two","startTime":2896.77,"endTime":2899.11,"body":"up to a maximum of 21 million Bitcoin."},{"speaker":"Problem number two","startTime":2899.11,"endTime":2903.43,"body":"That's a upper limit set by the"},{"speaker":"Problem number two","startTime":2899.11,"endTime":2903.43,"body":"system to prevent inflation."},{"speaker":"Problem number two","startTime":2903.43,"endTime":2904.99,"body":"But there is a problem."},{"speaker":"Problem number two","startTime":2904.99,"endTime":2909.37,"body":"The problem is maybe some"},{"speaker":"Problem number two","startTime":2904.99,"endTime":2909.37,"body":"nefarious miner comes along"},{"speaker":"Problem number two","startTime":2909.37,"endTime":2912.64,"body":"and changes the one Bitcoin to 100 Bitcoin"},{"speaker":"Problem number two","startTime":2912.64,"endTime":2914.443,"body":"after the block is mined."},{"speaker":"Problem number two","startTime":2915.73,"endTime":2918.1,"body":"Blocks being mined, the"},{"speaker":"Problem number two","startTime":2915.73,"endTime":2918.1,"body":"one Bitcoin is gone,"},{"speaker":"Problem number two","startTime":2918.1,"endTime":2921.404,"body":"and now suddenly Maya has 100 Bitcoin."},{"speaker":"Problem number two","startTime":2921.404,"endTime":2922.69,"body":"It means they're going"},{"speaker":"Problem number two","startTime":2921.404,"endTime":2922.69,"body":"through the same system,"},{"speaker":"Problem number two","startTime":2922.69,"endTime":2926.2,"body":"they're going to hash blah"},{"speaker":"Problem number two","startTime":2922.69,"endTime":2926.2,"body":"blah, blah, and get on with it."},{"speaker":"Problem number two","startTime":2926.2,"endTime":2928.39,"body":"How do I solve that problem?"},{"speaker":"Problem number two","startTime":2928.39,"endTime":2931.45,"body":"The answer is actually"},{"speaker":"Problem number two","startTime":2928.39,"endTime":2931.45,"body":"surprisingly simple."},{"speaker":"Problem number two","startTime":2931.45,"endTime":2936.45,"body":"The answer is I go back to this one here,"},{"speaker":"Problem number two","startTime":2936.73,"endTime":2938.74,"body":"I have my hash for this."},{"speaker":"Problem number two","startTime":2938.74,"endTime":2940.783,"body":"I take this hash number,"},{"speaker":"Problem number two","startTime":2941.89,"endTime":2946.813,"body":"and add it to the beginning"},{"speaker":"Problem number two","startTime":2941.89,"endTime":2946.813,"body":"of the next block."},{"speaker":"Problem number two","startTime":2951.55,"endTime":2952.81,"body":"This is a next block."},{"speaker":"Problem number two","startTime":2952.81,"endTime":2955.9,"body":"Say, Gresham owes Babbage for a computer"},{"speaker":"Problem number two","startTime":2955.9,"endTime":2958.783,"body":"or Babbage owes Kelvin"},{"speaker":"Problem number two","startTime":2955.9,"endTime":2958.783,"body":"for an electricity bill."},{"speaker":"Problem number two","startTime":2960.79,"endTime":2965.11,"body":"You can take that and put in"},{"speaker":"Problem number two","startTime":2960.79,"endTime":2965.11,"body":"a hash coming out right here."},{"speaker":"Problem number two","startTime":2965.11,"endTime":2967.51,"body":"So, in other words, if you go back here"},{"speaker":"Problem number two","startTime":2967.51,"endTime":2970.333,"body":"and change one Bitcoin to 100 bitcoin,"},{"speaker":"Problem number two","startTime":2971.92,"endTime":2976.15,"body":"this hash will change,"},{"speaker":"Problem number two","startTime":2971.92,"endTime":2976.15,"body":"but this hash will not,"},{"speaker":"Problem number two","startTime":2976.15,"endTime":2978.22,"body":"because this is the original hash."},{"speaker":"Problem number two","startTime":2978.22,"endTime":2980.41,"body":"In other words, if I"},{"speaker":"Problem number two","startTime":2978.22,"endTime":2980.41,"body":"want to change this hash,"},{"speaker":"Problem number two","startTime":2980.41,"endTime":2984.19,"body":"I have to go, take this previous hash,"},{"speaker":"Problem number two","startTime":2984.19,"endTime":2987.16,"body":"put it into the next one and redo it."},{"speaker":"Problem number two","startTime":2987.16,"endTime":2990.1,"body":"I have to do this fast"},{"speaker":"Problem number two","startTime":2987.16,"endTime":2990.1,"body":"enough that I can catch up"},{"speaker":"Problem number two","startTime":2990.1,"endTime":2994.813,"body":"with everybody else who's"},{"speaker":"Problem number two","startTime":2990.1,"endTime":2994.813,"body":"hashing faster than me."},{"speaker":"Problem number two","startTime":2995.8,"endTime":2998.25,"body":"In other words, let me"},{"speaker":"Problem number two","startTime":2995.8,"endTime":2998.25,"body":"put it in a different way."},{"speaker":"Problem number two","startTime":2999.28,"endTime":3004.14,"body":"If I'm hashing, let's say,"},{"speaker":"Problem number two","startTime":2999.28,"endTime":3004.14,"body":"block 79, I make a mistake,"},{"speaker":"Problem number two","startTime":3004.14,"endTime":3005.91,"body":"I change block 79,"},{"speaker":"Problem number two","startTime":3005.91,"endTime":3009.21,"body":"but everybody else is working on block 91,"},{"speaker":"Problem number two","startTime":3009.21,"endTime":3011.04,"body":"I have to change block 79,"},{"speaker":"Problem number two","startTime":3011.04,"endTime":3012.33,"body":"then I have to change block 80,"},{"speaker":"Problem number two","startTime":3012.33,"endTime":3015.57,"body":"because block 80 is chained to block 79."},{"speaker":"Problem number two","startTime":3015.57,"endTime":3017.49,"body":"That's what we mean by blockchain,"},{"speaker":"Problem number two","startTime":3017.49,"endTime":3019.56,"body":"because the blocks are chained together"},{"speaker":"Problem number two","startTime":3019.56,"endTime":3020.55,"body":"because of the headers."},{"speaker":"Problem number two","startTime":3020.55,"endTime":3021.72,"body":"I have to do this fast enough,"},{"speaker":"Problem number two","startTime":3021.72,"endTime":3025.89,"body":"before people stop finishing"},{"speaker":"Problem number two","startTime":3021.72,"endTime":3025.89,"body":"up the block 91 and 92."},{"speaker":"Problem number two","startTime":3025.89,"endTime":3027.87,"body":"People are adding on blocks at the end."},{"speaker":"Problem number two","startTime":3027.87,"endTime":3029.52,"body":"There's nobody who can do this."},{"speaker":"Problem number two","startTime":3029.52,"endTime":3032.49,"body":"That's one of the reasons why these things"},{"speaker":"Problem number two","startTime":3032.49,"endTime":3034.56,"body":"are so difficult to do."},{"speaker":"Problem number two","startTime":3034.56,"endTime":3036.393,"body":"Impossible to break a blockchain."},{"speaker":"Problem number two","startTime":3037.29,"endTime":3040.59,"body":"Overall, what have we seen?"},{"speaker":"Problem number two","startTime":3040.59,"endTime":3042.66,"body":"Romeo and Juliet are sending"},{"speaker":"Problem number two","startTime":3040.59,"endTime":3042.66,"body":"letters to each other."},{"speaker":"Problem number two","startTime":3042.66,"endTime":3044.1,"body":"What problems have they solved?"},{"speaker":"Problem number two","startTime":3044.1,"endTime":3045.84,"body":"Cryptography allows them to solve"},{"speaker":"Problem number two","startTime":3045.84,"endTime":3047.43,"body":"these first three problems."},{"speaker":"Problem number two","startTime":3047.43,"endTime":3049.05,"body":"They show that no one"},{"speaker":"Problem number two","startTime":3047.43,"endTime":3049.05,"body":"else can read the letters"},{"speaker":"Problem number two","startTime":3049.05,"endTime":3051.63,"body":"that are completely anonymous."},{"speaker":"Problem number two","startTime":3051.63,"endTime":3053.91,"body":"Second thing, hashing."},{"speaker":"Problem number two","startTime":3053.91,"endTime":3056.7,"body":"The letter is not garbled during sending."},{"speaker":"Problem number two","startTime":3056.7,"endTime":3060.39,"body":"Third, there is mining and verification."},{"speaker":"Problem number two","startTime":3060.39,"endTime":3063.03,"body":"They are sure that Romeo or Juliet"},{"speaker":"Problem number two","startTime":3063.03,"endTime":3067.473,"body":"is not writing the same letter"},{"speaker":"Problem number two","startTime":3063.03,"endTime":3067.473,"body":"to five other girls or boys."},{"speaker":"Problem number two","startTime":3070.404,"endTime":3073.92,"body":"This is the essence of"},{"speaker":"Problem number two","startTime":3070.404,"endTime":3073.92,"body":"how a blockchain works."},{"speaker":"Problem number two","startTime":3073.92,"endTime":3076.02,"body":"Once it's recorded on a blockchain,"},{"speaker":"Problem number two","startTime":3076.02,"endTime":3079.59,"body":"it's impossible to change that blockchain."},{"speaker":"Problem number two","startTime":3079.59,"endTime":3080.79,"body":"That means, essentially,"},{"speaker":"Problem number two","startTime":3080.79,"endTime":3082.56,"body":"you can write messages in blockchain,"},{"speaker":"Problem number two","startTime":3082.56,"endTime":3084.39,"body":"you can write contracts in blockchain."},{"speaker":"Problem number two","startTime":3084.39,"endTime":3087.6,"body":"Remember, the hash will"},{"speaker":"Problem number two","startTime":3084.39,"endTime":3087.6,"body":"take any length of contract"},{"speaker":"Problem number two","startTime":3087.6,"endTime":3092.267,"body":"and compress it to 10"},{"speaker":"Problem number two","startTime":3087.6,"endTime":3092.267,"body":"digits, or 256 in digits."},{"speaker":"Problem number two","startTime":3094.86,"endTime":3098.46,"body":"By the way, people have also"},{"speaker":"Problem number two","startTime":3094.86,"endTime":3098.46,"body":"put declarations of love"},{"speaker":"Problem number two","startTime":3098.46,"endTime":3099.42,"body":"into blockchains."},{"speaker":"Problem number two","startTime":3099.42,"endTime":3101.46,"body":"How do you do that? Well, it's easy."},{"speaker":"Problem number two","startTime":3101.46,"endTime":3105.3,"body":"You write a long letter in a blockchain,"},{"speaker":"Problem number two","startTime":3105.3,"endTime":3109.623,"body":"and then you send some money"},{"speaker":"Problem number two","startTime":3105.3,"endTime":3109.623,"body":"to a non-existent address."},{"speaker":"Problem number two","startTime":3110.55,"endTime":3112.26,"body":"That person will never cash the money."},{"speaker":"Problem number two","startTime":3112.26,"endTime":3114.36,"body":"It's a non-existent address."},{"speaker":"Problem number two","startTime":3112.26,"endTime":3114.36,"body":"You don't send much money."},{"speaker":"Problem number two","startTime":3114.36,"endTime":3115.62,"body":"Maybe you send 10 cents,"},{"speaker":"Problem number two","startTime":3115.62,"endTime":3118.71,"body":"but then inside the"},{"speaker":"Problem number two","startTime":3115.62,"endTime":3118.71,"body":"blockchain that's preserved,"},{"speaker":"Problem number two","startTime":3118.71,"endTime":3120.697,"body":"that message is preserved,"},{"speaker":"Problem number two","startTime":3118.71,"endTime":3120.697,"body":"and you can say,"},{"speaker":"Problem number two","startTime":3120.697,"endTime":3122.28,"body":"\"I love Juliet,\" or whatever."},{"speaker":"Problem number two","startTime":3122.28,"endTime":3125.64,"body":"The problem happens, of course,"},{"speaker":"Problem number two","startTime":3122.28,"endTime":3125.64,"body":"if you stop loving Juliet,"},{"speaker":"Problem number two","startTime":3125.64,"endTime":3127.53,"body":"then you can't get rid of that line."},{"speaker":"Problem number two","startTime":3127.53,"endTime":3128.943,"body":"It's there forever."},{"speaker":"Problem number two","startTime":3129.84,"endTime":3131.22,"body":"You have to say, \"Well, that person"},{"speaker":"Problem number two","startTime":3131.22,"endTime":3132.9,"body":"I referred to as Juliet earlier,"},{"speaker":"Problem number two","startTime":3132.9,"endTime":3134.28,"body":"please replace that with somebody else.\""},{"speaker":"Problem number two","startTime":3134.28,"endTime":3136.38,"body":"But you have to write new"},{"speaker":"Problem number two","startTime":3134.28,"endTime":3136.38,"body":"line in the blockchain."},{"speaker":"Problem number two","startTime":3136.38,"endTime":3138.21,"body":"So please, if you do have that,"},{"speaker":"Problem number two","startTime":3138.21,"endTime":3141.003,"body":"do not say something you do not mean."},{"speaker":"Problem number two","startTime":3142.35,"endTime":3144.24,"body":"Alright, let's conclude."},{"speaker":"Problem number two","startTime":3144.24,"endTime":3146.1,"body":"What can we conclude from this?"},{"speaker":"Problem number two","startTime":3146.1,"endTime":3147.57,"body":"The biggest thing I guess we can conclude"},{"speaker":"Problem number two","startTime":3147.57,"endTime":3152.57,"body":"is if this Shakespeare had"},{"speaker":"Problem number two","startTime":3147.57,"endTime":3152.57,"body":"access to this kind of technology"},{"speaker":"Problem number two","startTime":3153.03,"endTime":3155.1,"body":"back in the 1590s,"},{"speaker":"Problem number two","startTime":3155.1,"endTime":3157.8,"body":"there would've been no"},{"speaker":"Problem number two","startTime":3155.1,"endTime":3157.8,"body":"Romeo and Juliet written,"},{"speaker":"Problem number two","startTime":3157.8,"endTime":3159.933,"body":"and that would've been a tragedy."},{"speaker":"Problem number two","startTime":3163.32,"endTime":3164.153,"body":"Thank you."},{"speaker":"Problem number two","startTime":3165.682,"endTime":3168.682,"body":"(audience applauds)"},{"speaker":"Problem number two","startTime":3169.652,"endTime":3171.99,"body":"- I'm going to start with"},{"speaker":"Problem number two","startTime":3169.652,"endTime":3171.99,"body":"some online questions,"},{"speaker":"Problem number two","startTime":3171.99,"endTime":3174.697,"body":"and the first online question I have is,"},{"speaker":"Problem number two","startTime":3174.697,"endTime":3177.663,"body":"\"Professor Rao, do you own Bitcoin?\""},{"speaker":"Problem number two","startTime":3180.832,"endTime":3182.88,"body":"Have you ever owned Bitcoin?"},{"speaker":"Problem number two","startTime":3180.832,"endTime":3182.88,"body":"And that's from Wilma."},{"speaker":"Problem number two","startTime":3182.88,"endTime":3185.31,"body":"- It's a very good question"},{"speaker":"Problem number two","startTime":3182.88,"endTime":3185.31,"body":"and the answer is yes."},{"speaker":"Problem number two","startTime":3185.31,"endTime":3189.12,"body":"I owned past tense Bitcoin."},{"speaker":"Problem number two","startTime":3189.12,"endTime":3191.49,"body":"In fact, I bought this in 2013,"},{"speaker":"Problem number two","startTime":3191.49,"endTime":3193.77,"body":"when Bitcoin was just first starting out."},{"speaker":"Problem number two","startTime":3193.77,"endTime":3196.83,"body":"It was $150 per Bitcoin at that time."},{"speaker":"Problem number two","startTime":3196.83,"endTime":3201.66,"body":"I did buy some, and"},{"speaker":"Problem number two","startTime":3196.83,"endTime":3201.66,"body":"unfortunately I also wanted"},{"speaker":"Problem number two","startTime":3201.66,"endTime":3202.5,"body":"to see how it works."},{"speaker":"Problem number two","startTime":3202.5,"endTime":3205.92,"body":"So, in 2015 when it was"},{"speaker":"Problem number two","startTime":3202.5,"endTime":3205.92,"body":"still $150 per Bitcoin,"},{"speaker":"Problem number two","startTime":3205.92,"endTime":3209.01,"body":"I went to San Francisco,"},{"speaker":"Problem number two","startTime":3205.92,"endTime":3209.01,"body":"I bought some pizza,"},{"speaker":"Problem number two","startTime":3209.01,"endTime":3211.11,"body":"I bought a pair of pants,"},{"speaker":"Problem number two","startTime":3211.11,"endTime":3214.86,"body":"and basically now, effectively,"},{"speaker":"Problem number two","startTime":3211.11,"endTime":3214.86,"body":"my Bitcoin is zero."},{"speaker":"Problem number two","startTime":3214.86,"endTime":3217.2,"body":"I do know that, in 2017,"},{"speaker":"Problem number two","startTime":3217.2,"endTime":3220.77,"body":"when the price of Bitcoin"},{"speaker":"Problem number two","startTime":3217.2,"endTime":3220.77,"body":"went to $20,000 per Bitcoin,"},{"speaker":"Problem number two","startTime":3220.77,"endTime":3223.29,"body":"my wife, she said, \"Okay, we are rich.\""},{"speaker":"Problem number two","startTime":3223.29,"endTime":3224.81,"body":"And I said, \"Oh not quite.\""},{"speaker":"Problem number two","startTime":3228.814,"endTime":3230.723,"body":"- I'm glad to see your wife is still here,"},{"speaker":"Problem number two","startTime":3231.572,"endTime":3233.222,"body":"and has a blockchain love letter."},{"speaker":"Problem number two","startTime":3234.21,"endTime":3235.23,"body":"One more question online,"},{"speaker":"Problem number two","startTime":3235.23,"endTime":3237.21,"body":"and I'll open up to the audience as well,"},{"speaker":"Problem number two","startTime":3237.21,"endTime":3241.29,"body":"which is, interesting that"},{"speaker":"Problem number two","startTime":3237.21,"endTime":3241.29,"body":"you talked about trust here."},{"speaker":"A question from Leo online","startTime":3243.337,"endTime":3246.39,"body":"\"Would a quantum computer be able"},{"speaker":"A question from Leo online","startTime":3246.39,"endTime":3249.9,"body":"and be used to track"},{"speaker":"A question from Leo online","startTime":3246.39,"endTime":3249.9,"body":"what is a private key?\""},{"speaker":"A question from Leo online","startTime":3249.9,"endTime":3251.067,"body":"- Not track what is a private key."},{"speaker":"A question from Leo online","startTime":3251.067,"endTime":3253.88,"body":"You can already track what a key is."},{"speaker":"A question from Leo online","startTime":3253.88,"endTime":3255.09,"body":"You can track all the public keys,"},{"speaker":"A question from Leo online","startTime":3255.09,"endTime":3256.56,"body":"but the question I think is more,"},{"speaker":"A question from Leo online","startTime":3256.56,"endTime":3259.62,"body":"can a quantum computer"},{"speaker":"A question from Leo online","startTime":3256.56,"endTime":3259.62,"body":"break the encryption method?"},{"speaker":"A question from Leo online","startTime":3259.62,"endTime":3261.0,"body":"And in theory, yes,"},{"speaker":"A question from Leo online","startTime":3261.0,"endTime":3263.04,"body":"because prime number factorization"},{"speaker":"A question from Leo online","startTime":3263.04,"endTime":3265.14,"body":"is a problem which is relatively easy"},{"speaker":"A question from Leo online","startTime":3265.14,"endTime":3267.48,"body":"for a quantum computer to break,"},{"speaker":"A question from Leo online","startTime":3267.48,"endTime":3271.62,"body":"but there are no quantum"},{"speaker":"A question from Leo online","startTime":3267.48,"endTime":3271.62,"body":"computers out there."},{"speaker":"A question from Leo online","startTime":3271.62,"endTime":3274.53,"body":"Hopefully, that is a problem"},{"speaker":"A question from Leo online","startTime":3271.62,"endTime":3274.53,"body":"which needs to be solved,"},{"speaker":"A question from Leo online","startTime":3274.53,"endTime":3277.86,"body":"but not for the immediate future."},{"speaker":"A question from Leo online","startTime":3277.86,"endTime":3278.934,"body":"- [Audience] It could just be"},{"speaker":"A question from Leo online","startTime":3278.934,"endTime":3279.767,"body":"because I don't understand it properly."},{"speaker":"A question from Leo online","startTime":3279.767,"endTime":3281.147,"body":"I was just asking, with the mining,"},{"speaker":"A question from Leo online","startTime":3281.147,"endTime":3284.103,"body":"do they have to physically plug stuff in?"},{"speaker":"A question from Leo online","startTime":3284.942,"endTime":3286.563,"body":"I would assume-"},{"speaker":"A question from Leo online","startTime":3284.942,"endTime":3286.563,"body":"- No, no, no."},{"speaker":"A question from Leo online","startTime":3286.563,"endTime":3287.76,"body":"Very good question."},{"speaker":"A question from Leo online","startTime":3287.76,"endTime":3289.95,"body":"So no, you don't physically type stuff in."},{"speaker":"A question from Leo online","startTime":3289.95,"endTime":3291.63,"body":"That was to show how slow it is."},{"speaker":"A question from Leo online","startTime":3291.63,"endTime":3295.413,"body":"What you technically have are"},{"speaker":"A question from Leo online","startTime":3291.63,"endTime":3295.413,"body":"massive ranks of computers,"},{"speaker":"A question from Leo online","startTime":3296.88,"endTime":3298.41,"body":"You have factories"},{"speaker":"A question from Leo online","startTime":3298.41,"endTime":3302.07,"body":"with just units meant to process this."},{"speaker":"A question from Leo online","startTime":3302.07,"endTime":3304.32,"body":"That means, by the way,"},{"speaker":"A question from Leo online","startTime":3302.07,"endTime":3304.32,"body":"that has a consequence."},{"speaker":"A question from Leo online","startTime":3304.32,"endTime":3306.48,"body":"The consequence is Bitcoin mining"},{"speaker":"A question from Leo online","startTime":3306.48,"endTime":3309.81,"body":"is one of the most environmentally"},{"speaker":"A question from Leo online","startTime":3306.48,"endTime":3309.81,"body":"unsustainable activities"},{"speaker":"A question from Leo online","startTime":3309.81,"endTime":3310.643,"body":"there is,"},{"speaker":"A question from Leo online","startTime":3310.643,"endTime":3312.69,"body":"because what they're doing"},{"speaker":"A question from Leo online","startTime":3310.643,"endTime":3312.69,"body":"is using massive amounts"},{"speaker":"A question from Leo online","startTime":3312.69,"endTime":3316.26,"body":"of energy to solve a"},{"speaker":"A question from Leo online","startTime":3312.69,"endTime":3316.26,"body":"rather meaningless problem."},{"speaker":"A question from Leo online","startTime":3316.26,"endTime":3317.31,"body":"So, essentially,"},{"speaker":"A question from Leo online","startTime":3317.31,"endTime":3322.31,"body":"you end up consuming as much electricity."},{"speaker":"A question from Leo online","startTime":3322.44,"endTime":3324.42,"body":"Bitcoin mining at the moment will consume"},{"speaker":"A question from Leo online","startTime":3324.42,"endTime":3327.27,"body":"as much electricity as the"},{"speaker":"A question from Leo online","startTime":3324.42,"endTime":3327.27,"body":"entire country of Switzerland."},{"speaker":"A question from Leo online","startTime":3329.91,"endTime":3333.703,"body":"One of the big advantages"},{"speaker":"A question from Leo online","startTime":3329.91,"endTime":3333.703,"body":"which Ether Merge"},{"speaker":"A question from Leo online","startTime":3333.703,"endTime":3336.78,"body":"had in September was that they shifted"},{"speaker":"A question from Leo online","startTime":3336.78,"endTime":3337.743,"body":"from what we call a proof of work"},{"speaker":"A question from Leo online","startTime":3337.743,"endTime":3339.9,"body":"to a proof of stakes stage."},{"speaker":"A question from Leo online","startTime":3339.9,"endTime":3343.05,"body":"And that dropped the electricity"},{"speaker":"A question from Leo online","startTime":3339.9,"endTime":3343.05,"body":"consumption dramatically"},{"speaker":"A question from Leo online","startTime":3343.05,"endTime":3343.883,"body":"for Ether."},{"speaker":"A question from Leo online","startTime":3343.883,"endTime":3345.6,"body":"I will talk about that in January."},{"speaker":"A question from Leo online","startTime":3345.6,"endTime":3346.71,"body":"But you're absolutely right."},{"speaker":"A question from Leo online","startTime":3346.71,"endTime":3348.96,"body":"This is a major environmental issue."},{"speaker":"A question from Leo online","startTime":3348.96,"endTime":3350.01,"body":"You don't do this by hand,"},{"speaker":"A question from Leo online","startTime":3350.01,"endTime":3351.963,"body":"I was just showing you how to do it."},{"speaker":"A question from Leo online","startTime":3353.398,"endTime":3354.231,"body":"- [Audience] So, if it can be performed"},{"speaker":"A question from Leo online","startTime":3354.231,"endTime":3355.413,"body":"by a majority attack?"},{"speaker":"A question from Leo online","startTime":3356.4,"endTime":3357.66,"body":"- Yes, it can."},{"speaker":"A question from Leo online","startTime":3357.66,"endTime":3360.203,"body":"But the question is, it"},{"speaker":"A question from Leo online","startTime":3357.66,"endTime":3360.203,"body":"depends on the liquidity."},{"speaker":"A question from Leo online","startTime":3360.203,"endTime":3362.7,"body":"If you think about Bitcoin,"},{"speaker":"A question from Leo online","startTime":3362.7,"endTime":3364.92,"body":"Bitcoin is far too"},{"speaker":"A question from Leo online","startTime":3362.7,"endTime":3364.92,"body":"large and far too liquid"},{"speaker":"A question from Leo online","startTime":3364.92,"endTime":3367.08,"body":"in order to be done with"},{"speaker":"A question from Leo online","startTime":3364.92,"endTime":3367.08,"body":"the majority attack."},{"speaker":"A question from Leo online","startTime":3367.08,"endTime":3369.45,"body":"But if you have a small token,"},{"speaker":"A question from Leo online","startTime":3369.45,"endTime":3371.37,"body":"like something which is not liquid,"},{"speaker":"A question from Leo online","startTime":3371.37,"endTime":3373.02,"body":"something which is not easily traded,"},{"speaker":"A question from Leo online","startTime":3373.02,"endTime":3376.053,"body":"yes, there's several cases"},{"speaker":"A question from Leo online","startTime":3373.02,"endTime":3376.053,"body":"when that has happened."},{"speaker":"A question from Leo online","startTime":3377.624,"endTime":3380.13,"body":"You can buy 51% of it,"},{"speaker":"A question from Leo online","startTime":3380.13,"endTime":3385.13,"body":"and then suddenly issue a"},{"speaker":"A question from Leo online","startTime":3380.13,"endTime":3385.13,"body":"trillion credits in your own name,"},{"speaker":"A question from Leo online","startTime":3385.71,"endTime":3388.14,"body":"and then walk away with all the money."},{"speaker":"A question from Leo online","startTime":3388.14,"endTime":3390.42,"body":"There's several examples"},{"speaker":"A question from Leo online","startTime":3388.14,"endTime":3390.42,"body":"where that has happened."},{"speaker":"A question from Leo online","startTime":3390.42,"endTime":3393.54,"body":"But Bitcoin is the one case,"},{"speaker":"A question from Leo online","startTime":3393.54,"endTime":3396.18,"body":"Bitcoin and Ether, the two"},{"speaker":"A question from Leo online","startTime":3393.54,"endTime":3396.18,"body":"cases which are so liquid,"},{"speaker":"A question from Leo online","startTime":3396.18,"endTime":3397.53,"body":"it's impossible to do that."},{"speaker":"A question from Leo online","startTime":3398.82,"endTime":3401.22,"body":"- [Audience] Okay, thank you."},{"speaker":"A question from Leo online","startTime":3398.82,"endTime":3401.22,"body":"- At the moment."},{"speaker":"A question from Leo online","startTime":3401.22,"endTime":3403.05,"body":"- [Audience] You explained"},{"speaker":"A question from Leo online","startTime":3401.22,"endTime":3403.05,"body":"already what's happening:"},{"speaker":"A question from Leo online","startTime":3403.05,"endTime":3405.19,"body":"somebody has to solve"},{"speaker":"A question from Leo online","startTime":3403.05,"endTime":3405.19,"body":"a mathematical puzzle."},{"speaker":"A question from Leo online","startTime":3405.19,"endTime":3407.76,"body":"There must be a controlling mind."},{"speaker":"A question from Leo online","startTime":3407.76,"endTime":3409.98,"body":"There's got to be something behind it"},{"speaker":"A question from Leo online","startTime":3409.98,"endTime":3412.5,"body":"that sets the puzzle, and"},{"speaker":"A question from Leo online","startTime":3409.98,"endTime":3412.5,"body":"if you like, that marks it."},{"speaker":"A question from Leo online","startTime":3412.5,"endTime":3414.248,"body":"We don't seem to know that."},{"speaker":"A question from Leo online","startTime":3414.248,"endTime":3415.938,"body":"You mentioned Mr. Nakamoto,"},{"speaker":"A question from Leo online","startTime":3415.938,"endTime":3418.74,"body":"who people say is an"},{"speaker":"A question from Leo online","startTime":3415.938,"endTime":3418.74,"body":"Australian called Craig."},{"speaker":"A question from Leo online","startTime":3418.74,"endTime":3421.59,"body":"Surely we must know more"},{"speaker":"A question from Leo online","startTime":3418.74,"endTime":3421.59,"body":"about the controlling mind"},{"speaker":"A question from Leo online","startTime":3421.59,"endTime":3425.139,"body":"we clearly trust this whole-"},{"speaker":"A question from Leo online","startTime":3425.139,"endTime":3427.74,"body":"- Let me explain. That's"},{"speaker":"A question from Leo online","startTime":3425.139,"endTime":3427.74,"body":"actually a very good question."},{"speaker":"A question from Leo online","startTime":3427.74,"endTime":3429.66,"body":"There is no controlling mind."},{"speaker":"A question from Leo online","startTime":3427.74,"endTime":3429.66,"body":"That's the beauty of Bitcoin."},{"speaker":"A question from Leo online","startTime":3429.66,"endTime":3431.64,"body":"It's all technology."},{"speaker":"A question from Leo online","startTime":3431.64,"endTime":3433.41,"body":"The system wants to make sure"},{"speaker":"A question from Leo online","startTime":3433.41,"endTime":3435.78,"body":"that you're not creating money too fast."},{"speaker":"A question from Leo online","startTime":3435.78,"endTime":3437.34,"body":"That creates inflation."},{"speaker":"A question from Leo online","startTime":3437.34,"endTime":3439.98,"body":"So, what it does is measures the speed"},{"speaker":"A question from Leo online","startTime":3439.98,"endTime":3442.23,"body":"with which the problems are being solved."},{"speaker":"A question from Leo online","startTime":3442.23,"endTime":3444.3,"body":"If the problems are being solved too fast,"},{"speaker":"A question from Leo online","startTime":3444.3,"endTime":3446.52,"body":"it increases the"},{"speaker":"A question from Leo online","startTime":3444.3,"endTime":3446.52,"body":"difficulty of the problem."},{"speaker":"A question from Leo online","startTime":3446.52,"endTime":3448.05,"body":"It says, \"Not three leading zeros,"},{"speaker":"A question from Leo online","startTime":3448.05,"endTime":3449.94,"body":"but now I want four leading zeros.\""},{"speaker":"A question from Leo online","startTime":3449.94,"endTime":3453.78,"body":"So, it slows down. It's"},{"speaker":"A question from Leo online","startTime":3449.94,"endTime":3453.78,"body":"an automatic algorithm."},{"speaker":"A question from Leo online","startTime":3453.78,"endTime":3455.34,"body":"It just works for seeing how fast"},{"speaker":"A question from Leo online","startTime":3455.34,"endTime":3456.96,"body":"people are solving the problems."},{"speaker":"A question from Leo online","startTime":3456.96,"endTime":3457.793,"body":"- [Audience] But somebody"},{"speaker":"A question from Leo online","startTime":3456.96,"endTime":3457.793,"body":"wrote that program."},{"speaker":"A question from Leo online","startTime":3457.793,"endTime":3459.858,"body":"- Somebody did write that program."},{"speaker":"A question from Leo online","startTime":3459.858,"endTime":3461.02,"body":"- [Audience] Who is it?"},{"speaker":"A question from Leo online","startTime":3461.02,"endTime":3463.5,"body":"- Well, the first idea"},{"speaker":"A question from Leo online","startTime":3461.02,"endTime":3463.5,"body":"was Satoshi Nakamoto,"},{"speaker":"A question from Leo online","startTime":3463.5,"endTime":3466.26,"body":"but there's a whole group of"},{"speaker":"A question from Leo online","startTime":3463.5,"endTime":3466.26,"body":"people who worked on that idea."},{"speaker":"A question from Leo online","startTime":3466.26,"endTime":3468.51,"body":"Nakamoto came up with the original idea,"},{"speaker":"A question from Leo online","startTime":3468.51,"endTime":3471.27,"body":"but it was never meant"},{"speaker":"A question from Leo online","startTime":3468.51,"endTime":3471.27,"body":"to be a fully fledged"},{"speaker":"A question from Leo online","startTime":3471.27,"endTime":3472.2,"body":"operational system,"},{"speaker":"A question from Leo online","startTime":3472.2,"endTime":3474.78,"body":"mainly because he fixed"},{"speaker":"A question from Leo online","startTime":3472.2,"endTime":3474.78,"body":"several things in it,"},{"speaker":"A question from Leo online","startTime":3474.78,"endTime":3476.31,"body":"which need not have been done."},{"speaker":"A question from Leo online","startTime":3476.31,"endTime":3478.98,"body":"There's a maximum limit"},{"speaker":"A question from Leo online","startTime":3476.31,"endTime":3478.98,"body":"of 21 million Bitcoin"},{"speaker":"A question from Leo online","startTime":3478.98,"endTime":3480.78,"body":"which can be mined in the system."},{"speaker":"A question from Leo online","startTime":3480.78,"endTime":3481.95,"body":"That was because, at that time,"},{"speaker":"A question from Leo online","startTime":3481.95,"endTime":3483.03,"body":"there was a huge number."},{"speaker":"A question from Leo online","startTime":3483.03,"endTime":3485.22,"body":"He never thought we'd"},{"speaker":"A question from Leo online","startTime":3483.03,"endTime":3485.22,"body":"get anywhere near there."},{"speaker":"A question from Leo online","startTime":3485.22,"endTime":3487.143,"body":"We're almost there now."},{"speaker":"A question from Leo online","startTime":3488.107,"endTime":3490.95,"body":"It was an experimental"},{"speaker":"A question from Leo online","startTime":3488.107,"endTime":3490.95,"body":"system which took off,"},{"speaker":"A question from Leo online","startTime":3490.95,"endTime":3493.503,"body":"and now is incredibly popular."},{"speaker":"A question from Leo online","startTime":3494.43,"endTime":3498.09,"body":"So, if we had to go back and rewrite it,"},{"speaker":"A question from Leo online","startTime":3498.09,"endTime":3499.38,"body":"you might have picked a different system."},{"speaker":"A question from Leo online","startTime":3499.38,"endTime":3501.66,"body":"And that's what a lot of"},{"speaker":"A question from Leo online","startTime":3499.38,"endTime":3501.66,"body":"cryptocurrencies are doing,"},{"speaker":"A question from Leo online","startTime":3501.66,"endTime":3504.75,"body":"trying to solve the"},{"speaker":"A question from Leo online","startTime":3501.66,"endTime":3504.75,"body":"problems which Bitcoin had,"},{"speaker":"A question from Leo online","startTime":3504.75,"endTime":3506.943,"body":"which was never meant to solve."},{"speaker":"A question from Leo online","startTime":3508.89,"endTime":3510.81,"body":"- Thank you Professor Rao."},{"speaker":"A question from Leo online","startTime":3510.81,"endTime":3514.23,"body":"Love, Trust, and Crypto. Fascinating."},{"speaker":"A question from Leo online","startTime":3514.23,"endTime":3515.25,"body":"I'd like to thank Professor Rao"},{"speaker":"A question from Leo online","startTime":3515.25,"endTime":3518.46,"body":"for his insights, for"},{"speaker":"A question from Leo online","startTime":3515.25,"endTime":3518.46,"body":"simplifying the complex,"},{"speaker":"A question from Leo online","startTime":3518.46,"endTime":3521.67,"body":"and add an element of"},{"speaker":"A question from Leo online","startTime":3518.46,"endTime":3521.67,"body":"romanticism around it."},{"speaker":"A question from Leo online","startTime":3521.67,"endTime":3523.56,"body":"I'd ask you to give us round of applause,"},{"speaker":"A question from Leo online","startTime":3523.56,"endTime":3524.393,"body":"for professor Rao."},{"speaker":"A question from Leo online","startTime":3524.393,"endTime":3525.706,"body":"Thank you."},{"speaker":"A question from Leo online","startTime":3525.706,"endTime":3527.99,"body":"(audience applauds)"}]}