The names Alice and Bob are commonly used placeholders for archetypal characters in fields such as cryptography and physics. The names are used for convenience, since explanations such as "Person A wants to send a message to person B" can become difficult to follow, especially in complex systems involving many steps. Following the alphabet, the specific names have evolved into common parlance within these fields — helping technical topics to be explained in a more understandable fashion. Placeholder names are words that can refer to objects or people whose names are either irrelevant or unknown in the context which it is being discussed. ... The German Lorenz cipher machine, used in World War II for encryption of very high-level general staff messages Cryptography (or cryptology; derived from Greek κρυπτός kryptós hidden, and the verb γράφω gráfo write or λεγειν legein to speak) is the study of message secrecy. ... A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ...

In cryptography and computer security, there are a number of widely-used names for the participants in discussions and presentations about various protocols. The names are conventional, somewhat self-suggestive, sometimes humorous, and effectively act as metasyntactic variables. The German Lorenz cipher machine, used in World War II for encryption of very high-level general staff messages Cryptography (or cryptology; derived from Greek κρυπτός kryptós hidden, and the verb γράφω gráfo write or λεγειν legein to speak) is the study of message secrecy. ... This article “Secure computing” redirects here. ... A cryptographic protocol is an abstract or concrete protocol that performs a security-related function and applies cryptographic methods. ... A metasyntactic variable is a placeholder name, or a kind of alias term, commonly used to denote the subject matter under discussion, or a random member of a class of things under discussion. ...

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.

Often used by law school professors in Virginia in reference to Torts.

List of characters

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. Bruce Schneier Bruce Schneier (born January 15, 1963) is an American cryptographer, computer security specialist, and writer. ...

• 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.

Although an interactive proof system is not quite a cryptographic protocol, it is sufficiently related to mention the 'cast of characters' its literature features: Election People This box:      Professor Ronald Lorin Rivest (born 1947, Schenectady, New York) is a cryptographer, and is the Andrew and Erna Viterbi Professor of Computer Science at MITs Department of Electrical Engineering and Computer Science (CSAIL). ... Year 1978 (MCMLXXVIII) was a common year starting on Sunday (link displays the 1978 Gregorian calendar). ... The Association for Computing Machinery, or ACM, was founded in 1947 as the worlds first scientific and educational computing society. ... This article is about an algorithm for public-key encryption. ... Also: 1977 (album) by Ash. ... Also: 1977 (album) by Ash. ... Also: 1969 (Stargate SG-1) episode. ... This article is about the 1969 film. ... Quantum cryptography is an approach based on quantum physics for secure communications. ... “ISP” redirects here. ... In cryptography, an adversary (rarely opponent, enemy) is a malicious entity whose aim is to prevent the users of the cryptosystem from achieving their goal (primarily privacy, integrity and availability of data). ... In cryptography, a zero-knowledge proof or zero-knowledge protocol is an interactive method for one party to prove to another that a (usually mathematical) statement is true, without revealing anything other than the veracity of the statement. ... Vanna White (born Vanna Marie Rosich on February 18, 1957 is a American television personality, best known as the hostess and puzzle board operator on the long-running game show Wheel of Fortune. ... Wheel of Fortune is an American television game show originally devised by Merv Griffin, who also created Jeopardy!. The show debuted as a daytime program on NBC on January 6, 1975. ... For the band, see The Police. ... Mr. ... For other uses, see Noddy (disambiguation). ... Enid Mary Blyton (August 11, 1897–November 28, 1968) was a popular English childrens writer. ... Steganography is the art and science of writing hidden messages in such a way that no one apart from the intended recipient knows of the existence of the message; this is in contrast to cryptography, where the existence of the message itself is not disguised, but the content is obscured. ... ... A cryptographic protocol is an abstract or concrete protocol that performs a security-related function and applies cryptographic methods. ... In computational complexity theory, an interactive proof system is an abstract machine that models computation as the exchange of messages between two parties. ...

• Arthur 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 classes, namely MA and AM.

In computational complexity theory, an interactive proof system is an abstract machine that models computation as the exchange of messages between two parties. ... Merlin Ambrosius (Welsh: Myrddin Emrys (Merlin the Wise); also known as Myrddin Wyllt (Merlin the Wild), Merlin Caledonensis (Scottish Merlin), Merlinus, and Merlyn) is the personage best known as the mighty wizard featured in Arthurian legends, starting with Geoffrey of Monmouths Historia Regum Britanniae. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... A bronze Arthur in plate armour with visor raised and with jousting shield wearing Kastenbrust armour (early 15th century) by Peter Vischer, typical of later anachronistic depictions of Arthur. ... In computational complexity theory, a complexity class is a set of problems of related complexity. ... In computational complexity theory, an Arthur-Merlin protocol is an interactive proof system in which the verifiers coin tosses are constrained to be public (i. ... In computational complexity theory, an Arthur-Merlin protocol is an interactive proof system in which the verifiers coin tosses are constrained to be public (i. ...

Some articles using Alice and Bob explanations

• In communication:
  • Communication complexity
  • E-mail
  • SYN flood
• In cryptography:
  • Diffie-Hellman key exchange
  • Mental poker
  • One-time pad
  • Public key cryptography
  • Quantum cryptography
  • RSA
• In Law:
  • Lawburrows
• In physics:
  • Bell state
  • EPR paradox
  • Quantum teleportation

Communication is a process that allows organisms to exchange information by several methods. ... The notion of communication complexity (CC) was introduced by Yao in 1979, who investigated the following problem involving two separated parties (Alice and Bob). ... Wikipedia does not yet have an article with this exact name. ... A normal connection between a user (Alice) and a server. ... The German Lorenz cipher machine, used in World War II for encryption of very high-level general staff messages Cryptography (or cryptology; derived from Greek κρυπτός kryptós hidden, and the verb γράφω gráfo write or λεγειν legein to speak) is the study of message secrecy. ... Diffie-Hellman (D-H) key exchange is a cryptographic protocol that allows two parties that have no prior knowledge of each other to jointly establish a shared secret key over an insecure communications channel. ... The mental poker problem concerns how to play a fair game of poker without the need for a trusted dealer. ... Excerpt from a one-time pad. ... Public key cryptography is a form of cryptography which generally allows users to communicate securely without having prior access to a shared secret key, by using a pair of cryptographic keys, designated as public key and private key, which are related mathematically. ... Quantum cryptography is an approach based on quantum physics for secure communications. ... This article is about an algorithm for public-key encryption. ... For other uses, see Law (disambiguation). ... Lawburrows is a little-known civil action in Scots law initiated by one person afraid of anothers possible violence. ... A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ... The Bell states are a concept in quantum information science and represent the simplest possible examples of entanglement. ... In quantum mechanics, the EPR paradox is a thought experiment which challenged long-held ideas about the relation between the observed values of physical quantities and the values that can be accounted for by a physical theory. ... In quantum information, quantum teleportation, or entanglement-assisted teleportation, is a technique that transfers a quantum state to an arbitrarily distant location using a distributed entangled state and the transmission of some classical information. ...

See also

• Metasyntactic variable

A metasyntactic variable is a placeholder name, or a kind of alias term, commonly used to denote the subject matter under discussion, or a random member of a class of things under discussion. ...

References

• C.H. Lindsey, Regulation of Investigatory Powers Bill: Some Scenarios, 2000, [1].

External links

• A Method for Obtaining Digital Signatures and Public-Key Cryptosystems
• The Story of Alice and Bob
• Alice and Bob jokes (mainly Quantum Computing-related)
• Alice and Bob: IT's inseparable couple
• A short history of Bobs (story and slideshow) in the computing industry, from Alice & Bob to Microsoft Bob and Father of Ethernet Bob Metcalfe
• XKCD comic featuring Alice and Bob