Key-agreement protocol

A key exchange protocol is used in cryptography to two or more communication partners make to a shared secret key available. This can be done by someone a key transfers to all partners or by a new key is generated during the execution of the protocol. The key exchange protocol establishes the exact procedure. The key is then used to encrypt messages using symmetric encryption and decryption.

Key exchange protocols solve the so-called key distribution problem, which is to make the communication partners to a shared secret key available.

Originally, the only way to solve the key distribution problem is to replace a key person or sealed by a messenger. With the emergence of communication networks protocols were used as the symmetric Needham - Schroeder protocol between two parties, each with the same trusted third party has a shared secret key to exchange a session key. Another opportunity arose in 1975 when Whitfield Diffie developed the Diffie -Hellman key exchange, the first based on asymmetric cryptography protocol with Martin Hellman.

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