IETF RFC 2631 PDF

This document standardizes one particular Diffie-Hellman variant, based on the ANSI X9.42 draft, developed by the ANSI X9F1 working group. Diffie-Hellman is a key agreement algorithm used by two parties to agree on a shared secret. An algorithm for converting the shared secret into an arbitrary amount of keying material is provided. The resulting keying material is used as a symmetric encryption key. The Diffie-Hellman variant described requires the recipient to have a certificate, but the originator may have a static key pair (with the public key placed in a certificate) or an ephemeral key pair.