Diffie-Hellman is an asymmetric cipher defined in U.S. Patent 4,200,770 in 1977, the same year that IBM’s algorithm was selected as the Data Encryption Standard.
The Diffie-Hellman patent expired on 6 September, 1997.
The Diffie-Hellman algorithm is named after its creators: Whitfield Diffie and Martin Hellman.
ElGamal is a variant of Diffie-Hellman which was invented by Taher Elgamal.
