A provably secure identity-based signature scheme without PKG in the standard model

Compared with the traditional public key crypto-system, identity-based cryptosystem can simplify the key management procedure from the view point of the efficiency and convenience. But a trust PKG must been required in the ID-based cryptosystem and is unconditionally trusted. At present, Most of identity-based signature schemes are only proven to be secure in the random oracle model, but the security in random oracle model doesn't imply the security in the real world. Since the hash function is considered as a random generator. In this paper, we propose an efficient and provably secure identity-based signature scheme without trusted third party. Our scheme is existentially unforgeable against adaptive chosen message attacks under the computational Diffie-Hellman assumption in the standard model. Compared with the known strong identity-based scheme in the standard model, our scheme enjoys shorter signature size and less computation in terms of signing and verifying.