Many cryptographic protocols have been proposed, and many studies of them have been done. However, there is no study to identify constituent elements of cryptographic protocols that are elements of the protocols consist of. The constituent elements can be used for the basis of classification of already proposed cryptographic protocols, the basis of prediction of new cryptographic protocols, and the basis of formal verification for cryptographic protocols. This paper presents primitive constituent element of cryptographic protocols that is an element so that cryptographic protocol cannot accomplish its original tasks without it.