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.