An Improved ID-based Proxy Signature Scheme with Message Recovery

In 2012, Singh and Verma proposed an ID-based proxy signature scheme with message recovery. In this paper, we show that their scheme is vulnerable to the forgery attack, and an adversary can forge a valid proxy signature for any message with knowing a previous valid proxy signature. In addition, there is a security flaw in their proof. Furthermore, we propose an improved scheme that remedies the weakness of their scheme, and the improved scheme can be proved existentially unforgeable-adaptively chosen message and ID attack assuming the computational Diffie-Hellman problem is hard.