Alice and Bob

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Alice and Bob are synonyms for the sender and recipient of a message. They are used to simplify explanations in the fields of cryptography , network protocols, and physics . They represent metasyntactic variables and are used because descriptions with “Person A would like to send a message to person B ” quickly become confusing. "Alice and Bob" first appeared in 1978 in A Method for Obtaining Digital Signatures and Public-Key Cryptosystems by Ronald L. Rivest , Adi Shamir, and Leonard M. Adleman .

The names were chosen to match the first two letters of the alphabet , thus corresponding to the A and B subscribers in telecommunications. The names are also used in game theory papers to denote the players in a two-person game.

In the field of cryptography and computer security, there are a large number of names for participants in calls. The names are sometimes suggestive or contain a humorous undertone.

Role allocation

A distribution of roles to protagonists in an example often loosely follows the following assignment:

  • Alice and Bob represent common participants in the example scenario. The initiator of the object of consideration is usually Alice: she wants to send a message to Bob, for example.
  • Carol or Charlie and Dave (sometimes Ted ) serve as proxies for third and fourth parties of the example.
  • Eve , from engl. eavesdropper (in German Lauscher / Lauscherin ), is a passive attacker. It tries to overhear (and understand ) exchanged messages , but cannot change them.
  • Mallory , Marvin or Mallet , from Engl. malicious ( devious, insidious ), are active attackers. They want to or can actively intervene in what is happening, for example by forging messages or changing messages to be exchanged, e.g. B. by man-in-the-middle attack .
  • Oscar or Oskar , from Engl. opponent ( opponents ) can usually be seen Mallory equivalent
  • Peggy and Victor , are available for prover (about prover ) and verifier ( auditor ) and in protocols zero-knowledge used.
  • Trudy , from Engl. intruder ( Intruder ), is used in a similar role as Mallory, but mostly focused on the intrusion into an existing system.
  • Trent , from Engl. trusted entity , as a trustworthy third party (e.g. notary ).

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