47. One Time Pad: The Unbreakable Code

In this episode, we talk about the One Time System with Emily End. One time pad is what we've been looking for from all the methods this season- the unbreakable cipher. Not only is it impossible to break without help, it can be used to encipher something multiple times. But it does have two weaknesses... Also, in the story, more investigation is done by the Good Spy Ring into what is happening at the police station - and something unexpected comes to light, but their sneaking around has consequences!
 
The background music we used in this episode was "Documentary Story" by RomanSenykMusic, "Minimal Technology" by ComaStudio, "The Corporate Ambient" by ComaStudio, "Cyber Anxiety" by HoliznaCC0, "Brilliance" by ComaStudio, "Happy Diversion" by Ketsa, "Emotional Inspiring Epic Trailer" by Coma-Media, and "Bio Unit" by Bio Unit. Our theme music is from "Mosquito" by Caspar Babypants.

You can contact us here on Fanlist: https://fanlist.com/kidscodepodcast

or

 You can find Dr. Gareth's work at drgarethmoore.com. He has released many puzzle and cipher related books for kids, as well as a lot of stuff for adults, too. 

Thank you for listening.

Transcript

[00:00:00] Barnabas: This episode features the unbreakable code. You'll know what I mean in a second. Let's get right to it.

Welcome back to The Kids Code Podcast, the podcast about secret messages for kids. I'm Barnabas, your host, and with me as always, is Steve, your co-host. And Emily End. What are we talking about today, Steve?

[00:01:16] Steve: Today we're discussing the one time pad. It's one of the few, actually totally unbreakable ciphers that have been created.

There is one downside to it. We'll get to that later.

[00:01:44] Barnabas: Alright, then. Emily End, let's hear about this one time pad. 

[00:01:54] Emily End: The one time system, especially the one time pad, is a system in cryptography where a word or letter enciphered with a method of your choice is changed into a number, then added with a totally random string of numbers.

Usually the encoded or enciphered message is placed in blocks of five numbers. The key that is used to create the encipherment should never loop once enciphered this way, the message is either sent as numbers or converted back into letters. The technique will be explained more later on in the episode.

[00:02:38] Barnabas: Thanks for the explanation, Emily End

Here is the history.

Now you'd think that a system as simple as the one time pad. Where basically you just each have a pad of paper that is the same. It just has a list of random numbers on it that you use for enciphering. Your message would a pretty old technique, like, I mean, it's easy to do and it's pretty simple. But relative to a lot of other things, it's quite recent.

It was first described by Frank Miller in 1882, but the patent was from 1917 by Gilbert Vernam, who created the Vernam Cipher. A cipher that has some flaws and is kind of vulnerable because the key was a loop.

Joseph Mabo figured out that the method would be impossible to break if, and only if, the numbers used in the pad were completely random, and it was only used once.

Since then, the cipher has been used many times in different situations. One of the more outstanding ones was by KGB agents during the Cold War one time pads ended up turning up with a number of Soviet spies, Rudolph Abel. The highest ranking Russian agent ever captured in the US had one as a tiny booklet the size of a postage stamp, the FBI agents who arrested him, found it in his room at a hotel.

It was wrapped in a paper and hidden in a hollowed out block of wood that was covered with sandpaper like a sanding block 'cause the spy was posing as an artist that he'd casually thrown into the trash. In London in 1961, half a dozen one-time pads in the form of little scrolls were found in the cottage of Helen and Peter Kroger, two Soviet spies.

Later in 1961, Japanese police rounded up members of a North Korean communist spy ring and found one time pads in the things they'd captured. An atomic scientist who was accused of espionage against Britain for the Soviet Union was carrying two tiny one-time pads in a pack of cigarettes when he was caught at an airport in 1963.

Many more spies used them. A lot of ones that I haven't mentioned. Because it's such a simple and effective system.

Now, there are a few ways the one time system can be used. The first and the one that I like best is where you use some form of other code that you have to. Turn letters into a specific number.

Then you do the system where you add the number from the one time pad to the number you got from whatever code you'd used, and that is your solution. When you get past nine, when adding things together, instead of carrying over to the next digit, you simply reset and act like the extra numbers don't exist.

The second usage of the one time pad is where you have each letter, its own number. Often using the numbers cipher like we talked about in episode 20. Then you add the numbers from the one time pad, and in this case, there won't be anything with the carrying over, except if you get past 26, which would stand for Z.

Then you reset at the beginning of the alphabet.

Then you take the numbers you've gotten from this each time and convert them back into the letters like you're deciphering what you did the first time, but with different numbers, and then send those letters. This gives a lot of flexibility with the one time pad, but there are a couple of weaknesses.

The first is that those still extremely hard if the numbers used in the one time pad aren't completely random. Codebreakers can still decipher it, but you should be safe if you're creating the numbers yourself. Just try to make it as random as possible. So no, like 1, 2, 3, 4, 5.

It was found that the one-time pad groups, well statistically, 50% of the groups should start with a number on the lower side, between one and five and 50% should be starting with 6, 7, 8, 9, or zero. Um, often when humans are doing it, it's different. It's actually three quarters of the groups start with a lower number, which makes sense if the person typing these press the space between groups with their right hand. Also the amount of the time where after a low number, the next number will be. In the higher group is six times more than what it would be if it was really random and a number appearing two times in a row.

Is actually three times less when humans are doing it because it feels so non-random, but it turns out to be really random. There has to be more of those. This isn't saying that you need to manage to find a slow generator that can actually generate completely random numbers. You can do it yourself, and it is still practically unbreakable, but statistically, it's more likely to be beaten by cryptographers.

And the second and bigger weakness is the fact that you need to have the onetime pad. You can't just commit it all to memory and use it wherever, whenever. In your brain, you have to have the object, which is a big liability. If you get caught with the one time pad, then whoever caught you can read all the messages encrypted using the other one time pad that whoever would be sending messages to you or you would be sending messages to has been using. Whoever captured you can read all the messages that have been sent to you using the onetime pad. But without that, cryptanalysis is basically impossible. You can't even brute force it like you can with most things because if you went through every possible cipher text to try to decrypt the message, you'll actually end up with every possible plain text.

Which means that any message will be just as likely as another.

Another advantage to the system is not only that, it's easy to learn, but also the fact that seeing the length of the message. Only sort of helps you to figure out the content. This is true with a bunch of other forms of cryptography as well, but you can have nulls and things inside the message that in plain text are obviously nulls.

The technique is called padding where. You add more letters to make the message longer and to confuse cryptographers.

So if you look at an encrypted message with one time pad or a lot of other ciphers, all that you know is the longest the text could be, not how long it is. It could be much shorter.

[00:15:06] Steve: That's enough for this episode. Now, the story

[00:15:21] Barnabas: Previously on the Kids Code Podcast.

[00:15:28] Fred: Me and Al are going to be transferred to a different police department.

[00:15:38] TV Announcer: Barnabas is wanted for incorrect usage of the audio format. Wow.

[00:15:46] Codemaster Cole: I think Barnabas that you might be a criminal.

[00:15:51] Evil Ant: When The department was inspected, there were several things found against them and the two were both transferred to another department for the time being.

[00:16:09] Codemaster Cole: I dunno what he's talking about. But I don't think that guy's real name is Jeff. I think that might be one of our old, old enemies.

[00:16:26] Barnabas: Now let's get into this story.

Alright. All right. So I think we need to do a deeper investigation into the police department.

Steve had just told me what had happened at the police department. Ka the crow had identified the voice as the evil ant.

So if the evil ant is the chief, then one would suspect that something odd has happened. Now, of course it, it could just be a coincidence like we had with the ant who upholds justice in a previous season, but I doubt it. So Codemaster Cole, do you have a plan?

[00:17:28] Codemaster Cole: Yeah, I have a pretty good plan. The idea is that we sneak into the police department. Fred gave us a key during the night. Then we look at the records and we see if we can discover anything. Also, we managed to get a mole into the police department.

[00:18:00] Barnabas: Well, I hope he is good and he's actually on our side. Oh, I'm pretty sure that he's helped us in the past.

[00:18:12] Caw the Crow: We'll see. Now, we also have this problem with you being here.

[00:18:19] Barnabas: Yeah, that's true. We need to figure out some way to help me out. But one step at a time. You think you guys can do it? Yeah. Alright. See you in a day or two.

[00:18:44] Codemaster Cole: Got the key?

[00:18:47] Caw the Crow: Yes.

[00:18:48] Codemaster Cole: All right, let's sneak in the back here.

Hey Bob. Turn on the flashlight, but keep it dim. Okay?

Ah, here we are. I've been in here once. This is where they have the main computer that has the records from the police station on it. You think you can figure out how to get in Caw and Bob?

[00:19:33] Bob Bot: Absolutely.

[00:19:37] Caw the Crow: I just hacked the security cams. The one that's in here showed footage of someone typing in the password, so we should be able to get in.

I also disabled the security cams before coming in here.

We're in!

[00:20:04] Codemaster Cole: All right, let's look here. It's the police records

Guys, almost every single officer here has been hired in the last 30 days. And it shows that some of the names that are given by officers are actually aliases and yes, there it is. Chief. Yeah, that's the evil ant 

[00:20:49] Caw the Crow: I see every member of the bad spy ring here.

I guess we'd better check prison records then. 'cause I never learned they escaped.

It doesn't show anything. It doesn't look like they're there. But there is a guard on duty recently who's named Terrific Tim. Sound like anyone we know?

[00:21:29] Bob Bot: Well, that explains that. Now let's get out of here.

[00:21:44] Evil Ant: Thanks for coming my friends. I've been expecting you.

[00:22:02] Barnabas: I hope you like that story. Things sure are heating up. I think that's all for this episode. Nah, I'm kidding. We have some more about one time pads to talk about.

You know, they're called one time Pads because. They're supposed to only be used one time, right? The one time part means you have to get rid of the key after you use it, which usually means destroying it. Most of the time. Spies would burn it, but you are probably safe, like tearing it up and throwing it in the trash.

In fact, some one-time pads have been made on a substance that for the most part, works like paper, but is extremely flammable, which couldn't make it dangerous. But as far as I know, no accidents involving one time pads and fire have happened.

Also, you've probably heard me saying one time system instead of one time pad a few times in the episode, because it doesn't have to be used in pads. That's part of the amazing versatility of it. Other than your brain, you can use it on almost anything that. You can write on just probably a computer program isn't super safe, especially if you send the messages using the one time pad, using the same computer program as you have the key for the one time pad. Also, you might hear the word vernam cipher for the one time system, but though the one time system was patented by George Vernam. The Vernam Cipher is a different kind of cipher, also with a mostly running stream, but it can be broken by cryptographers.

The one time system is one of the most secure cipher techniques in the world. And it is one of the ones that people have discussed being one of the few safe and secure methods of cryptography after quantum computers are invented. Yep. That secure.

That's really all for this episode.

[00:25:27] Steve: Thanks for listening. If you have a facts about codes, do you wanna share? You've made a code and you want share it or something else? Contact us. There are links in the show notes.

[00:25:44] Barnabas: The sources we used in this episode were The Dark Game by Paul B Jenesco, the Code Breakers by David Kahn in the few assorted articles.

[00:26:00] Steve: Our next episode is another master message episode, the last one of this season, so stay tuned for that. 

[00:26:12] Barnabas: But until then, keep on cracking.