Analysis of Forgery Attack on One-Time Proxy Signature and the Improvement

In a recent paper, Yang et al. (Quant. Inf. Process. 13(9), 2007–2016, 2014) analyzed the security of one-time proxy signature scheme Wang and Wei (Quant. Inf. Process. 11(2), 455–463, 2012) and pointed out that it cannot satisfy the security requirements of unforgeability and undeniability because an eavesdropper Eve can forge a valid proxy signature on a message chosen by herself. However, we find that the so-called proxy message-signature pair forged by Eve is issued by the proxy signer in fact, and anybody can obtain it as a requester, which means that the forgery attack is not considered as a successful attack. Therefore, the conclusion that this scheme cannot satisfy the security requirements of proxy signature against forging and denying is not appropriate in this sense. Finally, we study the reason for the misunderstanding and clarify the security requirements for proxy signatures.