ID-based Chameleon Hash Scheme and Signature Without Key Escrow

An identity-based chameleon hash function without the key escrow problem is proposed. It not only achieves all the desired security properties of the traditional identity-based chameleon hashing but also removes the inherent escrow problem of identity-based systems. That is, the private key generator (PKG) can not find a collision of our proposed identity-based chameleon hash function. Moreover, an identity-based chameleon signature without the key escrow problem is given by adoption of the identity-based encryption and the identitybased signature without the key escrow. Besides, a security proof of the proposed chameleon hashing and signature scheme is given, showing that these schemes without the key escrow are collision resistance, semantically securand message hiding.