Why is Cryptocurrency Obsessed with Alice and Bob?

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Hello my friends. You are listening to the very first episode of “Explaining Cryptocurrency”. I am Jason Rigden and I am your host. Thank you so much for listening.

On this episode we will be talking about the two of most famous people in cryptography. The pair have been working together for decades. The have worked with almost every cryptography researcher in the world. I am of course talking about, Alice and Bob. And the most interesting thing about Alice and Bob is that they are not even real people.

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Ok, back to Alice and Bob. If you are studying cryptocurrency, you need to study cryptography. And if you have studied cryptography you have probably noticed a strange pattern. The names of the people used in examples are always the same. The scenario goes something like this, “Alice wants to send Bob a secret message. So Alice uses Bob’s public key to encrypt a message only he can read”. Sounds straight forward. Using actual human names helps make the concepts seem less abstract. It is a bit better then saying, “A wants to send B a secret message. So A uses B’s public key to encrypt a message only B can read”.

What is strange though is that everyone uses the same names. It is always Alice and Bob. It is never Ashley and Bruce. Or Adam and Bianca.

Well it all started in 1978. An article was published by Rivest, Shamir, and Adleman. It was called, “A method for obtaining digital signatures and public-key cryptosystems”. In it they wrote, “For our scenarios we suppose that A and B (also known as Alice and Bob) are two users of a public-key cryptosystem”. This was new. Previously most cryptographers just used simple symbols to represent sender and receiver. Simple symbols like A and B.

Cognitive load is a funny thing. Cryptography is a very complex topic. It takes quite a bit of mathematical knowledge just to understand how it works. Then there are long complex mathematical equations to understand. Yet people find that Alice is more memorable than A. For students especially, it helps with comprehension.

It also helps us create a story. Humans love stories much more than abstractions. Although some might say that every story is an abstraction but that is a topic for another podcast show.

So after 1978 the usage of Alice and Bob in academic papers steadily increased. And in 1988 a paper called, “Privacy Amplification by Public Discussion” by Bennet, Brassard, and Robert was published. In it the introduced a new character, Eve. Eve was an eavesdropper. While Alice and Bob are sending messages back and forth in our examples. Eve would be a passive attacker attempting to listen to those messages.

Soon Alice, Bob, and Eve would be joined by a whole family of imaginary people. There would be Charlie, Grace, Heidi and many more. Each with their own special functions.

For example Charlie is a third participant. So it would be Alice, Bob, and Charlie sending messages to each other. A, B, and C.

Another example is Grace. Grace is a representative of the government. So Alice and Bob are sending messages back and forth but Grace has access to a government mandated back door. This lets Grace read all the messages.

In real life many law enforcement agencies around the world want to have a back door into all encryption. Specifically, the FBI. They have been using fear tactics to lobby congress for decades. They want a software version of a golden key that will open any lock. Every legitimate cryptographer thinks this is a terrible idea.

Anyhow, I’m not going to apologize for getting political here. It’s impossible to talk about technology without talking about politics. Especially, when it comes to cryptocurrency.

So, back to Alice and Bob and their cadre of associates. These imaginary characters are so popular that they have transcended academia and entered pop culture. Geek culture but pop culture none the less. They have appeared in comics like XKCD, there are t-shirts, and even rap songs. Folks have even written back stories about the pair. Like James Gordon’s definitive biography of the pair in his, “After Dinner Speech”. Links to these wonderful artifacts are in the show notes.

It’s funny how common tropes are in computer science. From Alice and Bob to Hello World to Foo Bar. There is an almost endless supply of these patterns. I wonder how long each one will last. And, what new ones are being created right now. I really doubt the originators of Alice and Bob had any idea there were creating a cultural touchstone. Yet here we are four decades later. Still talking about these imaginary people passing around secrets.


Well, that is the end of episode number 1. Thanks for listening. If you enjoyed this episode may I ask you for a favor. This is a brand new show and I would love to get topics ideas from my listeners. So please, if you would, send me some cryptocurrency topic that you would like me to talk about. My contact details are in the show notes.

Once again this has been Explaining Cryptocurrency and I am Jason Rigden. I hope to talk to you again soon. Good Bye.

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