Efficient ID-based Signature Without Trusted PKG

In this paper, we introduce the exact concept of ID-based signature without trusted Private Key Generater(PKG), which solves the key escrow problem through binding two public key with a same identity. In this scheme, PKG is prevented from forging a legal user’s signature because he only generates the partially private key. Using Gap Diffie-Hellman (GDH) groups, we construct an efficient ID-based signature scheme without trusted PKG, which security relies on the hardness of the Computational Diffie-Hellman Problem (CDHP). More precisely, under the random oracle model, our scheme is proved to be secure against existential forgery on adaptively chosen message and ID attack, assuming CDHP is intractable. Our scheme not only eliminates the inherent key escrow problem but also has a higher efficiency than the existing schemes.