Diffie-Hellman key exchange

Diffie-Hellman key exchange is a cryptographic protocol which allows two parties that have no prior knowledge of each other to jointly establish a shared secret key over an insecure communications channel. This key can then be used to encrypt subsequent communications using a symmetric key cipher.

Related Topics:
Cryptographic protocol - Key - Communication - Symmetric key - Cipher

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Synonyms:

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• exponential key exchange
• Diffie-Hellman key agreement
• Diffie-Hellman key negotiation
• Diffie-Hellman key establishment

The scheme was first published publicly by Whitfield Diffie and Martin Hellman in 1976, although it later emerged that it had been discovered a few years earlier within GCHQ, the British signals intelligence agency, by Malcolm J. Williamson but was kept classified. In 2002, Hellman suggested the algorithm be called Diffie-Hellman-Merkle key exchange in recognition of Ralph Merkle's contribution to the invention of public-key cryptography (Hellman, 2002).

Related Topics:
Whitfield Diffie - Martin Hellman - 1976 - GCHQ - Malcolm J. Williamson - 2002 - Ralph Merkle - Public-key cryptography

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Although Diffie-Hellman key agreement itself is an anonymous (non-authenticated) key agreement protocol, it provides the basis for a variety of authenticated protocols, and is used to provide perfect forward secrecy in TLS's ephemeral modes.

Related Topics:
Key agreement - Perfect forward secrecy - TLS

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Diffie-Hellman key exchange: History of the protocol ►