This list is drawn mostly from the book Applied Cryptography by Bruce Schneier. Alice and Bob are archetypes in cryptography; Eve is also common. Names further down the alphabet are less common.
- Alice and Bob. Generally, Alice wants to send a message to Bob. These names were used by Ron Rivest in the 1978 Communications of the ACM article presenting the RSA cryptosystem, and in A Method for Obtaining Digital Signatures and Public-Key Cryptosystems published April 4, 1977, revised September 1, 1977 as technical Memo LCS/TM82 by MIT. Rivest denies that these names have any relation with the 1969 movie Bob & Carol & Ted & Alice as occasionally suggested by others.
- Carol or Charlie, as a third participant in communications. Thereafter, we often have Dave, a fourth participant, and so on alphabetically.
- Eve, an eavesdropper, is usually a passive attacker. While she can listen in on messages between Alice and Bob, she cannot modify them. In quantum cryptography, Eve may also represent the environment.
- Isaac, an Internet Service Provider (ISP).
- Ivan, an issuer (as in financial cryptography).
- Justin, from the justice system.
- Mallory, a malicious attacker; unlike Eve, Mallory can modify messages, substitute her own messages, replay old messages, and so on. The problem of securing a system against Mallory is much greater than against Eve. The names Marvin and Mallet can also be used for this role.
- Matilda, a merchant (as in e-commerce or financial cryptography).
- Oscar, an opponent, is usually taken as equivalent to Mallory.
- Pat or Peggy, a prover, and Victor, a verifier, often must interact in some way to show that the intended transaction has actually taken place. They are often found in zero-knowledge proofs. Another name pair sometimes used is Pat and Vanna (after the host and hostess on the Wheel of Fortune television show).
- Plod, a law enforcement officer (also “Officer Plod”) from the children’s fictional character Mr. Plod, in the Noddy books by Enid Blyton.
- Steve, sometimes used in reference to Steganography.
- Trent, a trusted arbitrator, is some kind of neutral third party, whose exact role varies with the protocol under discussion.
- Trudy, an intruder: another alternative to Mallory.
- Walter, a warden, may be needed to guard Alice and Bob in some respect, depending on the protocol being discussed.
- Zoe, often the last party to be involved in a cryptographic protocol.