For example , cryptographic application protocols often use one or more underlying Key-agreement protocols which are also sometimes themselves referred to as `` cryptographic protocols '' , like the Secure Sockets Layer ( SSL ) which uses what is known as the Diffie-Hellman key exchange , Diffie-Hellman may be seen as a complete cryptographic protocol in itself for other applications . There are other types of cryptographic protocols as well , and even the term itself has various different readings ; Cryptographic application protocols often use one or more underlying key agreement methods , which are also sometimes themselves referred to as `` cryptographic protocols '' . For instance , TLS employs what is known as the Diffie-Hellman key exchange , which although it is only a part of TLS per se , Diffie-Hellman may be seen as a complete cryptographic protocol in itself for other applications .