ID-based cryptographic schemes for user identification, digital signature, and key distribution

In 1984, A. Shamir introduced the concept of an identity-based cryptosystem. In this system, each user needs to visit a key authentication center (KAC) and identify himself before joining a communication network. Once a user is accepted, the KAC will provide him with a secret key. In this way, if a user wants to communicate with others, he or she only needs to know the identity of his communication partner and the public key of the KAC. There is no public file required in this system. However, Shamir did not succeed in constructing an identity-based cryptosystem, but only in constructing an identity-based signature scheme. The authors here propose three identity-based cryptographic schemes based on the discrete logarithm problem: the user identification scheme, the digital signature scheme, and the key distribution scheme. The schemes are based on the digital signature scheme of G.B. Agnew et al. (1990), which is reviewed