Published in 1976 by Diffie and Hellman, this is the earliest publicly known work that proposed the idea of a private key and a corresponding public key. DH is one of the earliest practical examples of public key exchange implemented within the field of cryptography. Method of exchanging cryptographic keys With Diffie-Hellman key exchange, two parties arrive at a common secret key, without passing the common secret key across the public channel.ĭiffie–Hellman key exchange is a mathematical method of securely exchanging cryptographic keys over a public channel and was one of the first public-key protocols as conceived by Ralph Merkle and named after Whitfield Diffie and Martin Hellman.