In Cryptography and Computer Security , there are a number of widely-used names for the participants in discussions and presentations about various Protocol s. The names are conventional, somewhat self-suggestive, sometimes humorous, and are, more or less, Metasyntactic Variable s.
In typical implementations of these protocols, it is understood that the actions attributed to characters such as Alice or Bob would not normally be carried out by human parties directly, but rather by a trusted automated agent (such as a computer program) on their behalf.
This list is drawn mostly from the book ''Applied Cryptography'' by Bruce Schneier . Alice and Bob are archetypes in cryptography; the names further down the alphabet not quite as much so.
- and '''Bob'''. Generally Alice wants to send a message to Bob. These names were invented by Ron Rivest for the 1978 ''Communications of the ACM '' article presenting the RSA cryptosystem. (The 1977 technical report on RSA did not use these names.) Rivest denies that these names have any relation with the 1969 movie '' Bob & Carol & Ted & Alice '' as occasionally suggested by others.
- , as a third participant in communications. Thereafter, we often have '''Dave''', a fourth participant, and so on alphabetically.
- , 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''.
- , an Internet Service Provider (ISP).
- , an ''issuer'' (as in financial cryptography).
- , from the ''justice'' system.
- , 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.
- , a ''merchant'' (as in ecommerce or financial cryptography).
- , an '' Opponent '', is usually taken as equivalent to Mallory.
- , see 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 Proof s. Another name pair sometimes used is '''Pat''' and '''Vanna''' (after the host and hostess on the '' Wheel Of Fortune '' television show).
- , a Law Enforcement officer (''P'' for ''police'', also "Officer Plod" from the children's TV show Noddy ).
- , sometimes used in reference to Steganography .
- , an intruder: another alternative to Mallory.
- , a ''trusted arbitrator'', is some kind of neutral third party, whose exact role varies with the protocol under discussion.
- , a ''warden'', may be needed to guard Alice and Bob in some respect, depending on the protocol being discussed.
- , often the last party to be involved in a Cryptographic Protocol .
Although an Interactive Proof System is not quite a cryptographic protocol, it is sufficiently related to mention the 'cast of characters' its literature features:
- and '''Merlin''': In IPSs , the prover has unbounded computational ability and is hence associated with Merlin , the powerful Wizard . He claims the truth of a statement, and Arthur , the wise king, questions him to verify the claim. These two characters also give the name for two Complexity Class es, namely MA and AM .
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