International Journal of Computer Theory and Engineering

Abstract

As a variation of ordinary digital signature scheme, a proxy signature scheme able a proxy signer to sign messages on behalf of the original signer. Proxy multi-signature is an extension of the basic proxy signature primitive and permits two or more entities to delegate their signing capabilities to the same other entity. In proxy multi-signature, many original signers can delegate their signing power to a proxy signer in such a way that the proxy signer can sign any message on behalf of original signers. In blind signature, the signer cannot make a linkage between the blind signature and the identity of the requester. Proxy blind multi-signature is the combination of proxy multi-signature and blind signature. Recently, Lu <i>et al</i>. presented a proxy blind multi-signature scheme which did not need a secure channel. However, in this paper, we show that Lu <i>et al</i>.'s scheme does not satisfy the unforgeability and also shown that their scheme is not secure against the original signer's forgery attack and the proxy signer's forgery attacks.