Simply: Who are Alice and Bob, and why are they mentioned in every Bitcoin-related article I read about that talks about Bitcoin transactions?

What is the history or mystery of these two?

  • 11
    First hit on google explains everything: en.wikipedia.org/wiki/Alice_and_Bob – Greg Hewgill May 16 '14 at 0:58
  • 5
    I had to upvote. This is the funniest question on the site. – Kinnard Hockenhull May 16 '14 at 3:00
  • 2
    This question appears to be off-topic because it is not Bitcoin or cryptocurrency specific and is trivially answered by a web search. – dchapes May 17 '14 at 11:43
  • Lacking research effort certainly, but I wouldn't say the question is off-topic: At last, it is a question about terminology/culture of the Bitcoin community (even though not exclusively so). I also found it somewhat amusing as Kinnard did, and found it useful in that by reading the link from the answer, I learned about the complete roster surrounding Alice and Bob. I must say I diverged quite significantly on my order book example. ;) – Murch May 19 '14 at 21:46
  • This made me lol. <3 – ecurrencyhodler May 21 '18 at 2:20

Fictional characters. Cryptography (and other) books use names like that often.


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Alice and Bob are placeholder characters corresponding to the letters of the alphabet. They are used especially in computer science to describe use-cases or scenarios. The scheme is used because it's more convenient to say "Alice sends money to Bob" than to say "Party A sends money to Party B". As each name has a different initial, diagrams can fall back to single letter labeling.

It's a well-known meme:

Obligatory XKCD

The list usually goes something like this: Alice, Bob, Charlie, Dave, Erin, Frank,…

Other names are used to represent attacker types or other recurring roles:

  • Carole, the oracle
  • Eve, the eavesdropper
  • Mallory, the man-in-the-middle attacker with malicious intent
  • Sybil, the attacker with lots of identities
  • Trent, the trusted entity
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