A realization scheme for the identity-based cryptosystem

Abstract

At the Crypto’84, Shamir has presented a new concept of the identity-based cryptosystem, but no idea is presented on the realization scheme. In this paper a new realization scheme of the modified identity-based cryptosystem has been proposed. The basic idea of the scheme is based on the discrete logarithm problem and the difficulty of factoring a large integer composed of two large primes. The scheme seems to be very secure if all members of the system keep their secret keys safe, but if a constant number of users conspire, the center secret will be disclosed, Then it has a close relation to the well-known “threshold scheme”. To cope with the conspiracy, the basic system is extended to get a new scheme of which “threshold” becomes higher. Detail considerations on the scheme are also given.