Key agreement refers to one form of key exchange (see also key encryption key) in which two or more users execute a protocol to securely share a resultant key value. As an alternative to key agreement, a key transport protocol may be used. The distinguishing feature of a key agreement protocol is that participating users each contribute an equal portion toward the computation of the resultant shared key value (as opposed to one user computing and distributing a key value to other users).
The original, and still most famous, protocol for key agreement was proposed by Diffie and Hellman (see Diffie–Hellman key agreement) along with their concept for public-key cryptography. Basically, users Alice and Bob send public-key values to one another over an insecure channel. Based on the knowledge of their corresponding private keys, they are able to correctly and securely compute a shared key value. An eavesdropper, however, is unable to similarly compute this key using only knowledge of the...
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References
Menezes, A., P. van Oorschot, and S. Vanstone (1997). Handbook of Applied Cryptography. CRC Press, Boca Raton, FL.
Stinson, D.R. (1995). Cryptography: Theory and Practice. CRC Press, Boca Raton, FL.
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Just, M. (2005). Key agreement. In: van Tilborg, H.C.A. (eds) Encyclopedia of Cryptography and Security. Springer, Boston, MA . https://doi.org/10.1007/0-387-23483-7_218
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