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1Fix the driver behind crashes, sound loss and screen glitches2Repair Windows errors before they cause bigger problems3Scan for outdated or missing drivers - takes under a minuteAlice and Bob are fictional stand-ins for participants in examples of cryptographic and other security protocols. Their names make it easier to follow who sends, receives, or processes a message. They identify roles in an example; they do not show that a protocol is secure.
What do Alice and Bob mean?
In a protocol example, Alice and Bob usually represent two parties communicating with one another. A writer can describe what each party sends or receives without repeatedly inventing new identities. As RFC 4949, the Internet Security Glossary, Version 2, puts it, they are “the parties that are most often called upon to illustrate the operation of bipartite security protocols.” The glossary notes that its definitions are the author’s, not an official IETF position.
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The names are labels, not fixed technical roles. Depending on the example, Alice might initiate a message or establish a key, while Bob receives it or takes part in the same exchange. Read the protocol description to learn what each one does.
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Cryptographic protocols and key establishment
Standards-related material uses Alice and Bob to explain key establishment, including examples involving key-encapsulation mechanisms (KEMs). NIST’s glossary entry for Alice and Bob gives examples drawn from cited standards; each definition should be understood in the context of the standard it references.
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Quantum key distribution
The same names also appear in explanations of quantum key distribution, where they serve as fictional participants in an exchange. A 2004 NIST explainer is one example. The names make the scenario easier to follow; they are not actual people.
Who else appears in these examples?
When a scenario needs more than two roles, authors may add other conventional names. The Jargon File lists examples such as:
- Eve: an eavesdropper who observes a communication.
- Mallory: a malicious active attacker who may interfere with messages.
- Trent: a trusted arbitrator.
- Peggy: a prover.
- Victor: a verifier.
These are explanatory mnemonics, not roles that every protocol must include. Their meanings depend on the scenario being described.
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No. Giving parties familiar names only makes an example easier to read. It does not establish that the protocol protects messages, authenticates participants, or meets any other security goal. Those conclusions depend on the protocol’s design and assumptions, which must be assessed separately.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How did Alice and Bob become standard examples?
Their exact first use is not established by the sources cited here, so a definitive inventor or origin date cannot be given. The Jargon File notes that Bruce Schneier’s Applied Cryptography, second edition (1996), included a table of cryptographic dramatis personae headed by Alice and Bob. That supports saying the book helped popularize the cast, not that it introduced the names.
For a broader reference, Schneier’s Applied Cryptography, second edition, is an optional follow-up; the Jargon File discusses its role in popularizing the dramatis personae: Jargon File: “Alice and Bob”.
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