一种改进的定向代理签名方案

在通常的代理签名方案中，任何人都可以验证代理签名的有效性。在定向代理签名方案中，由原始签名人指定一个人作为签名的接收者，以此来防止签名的滥用。当代理签名人产生签名后，只有指定的接收者可以对签名进行验证，进而接受签名。分析了Dai等定向代理签名方案，它不满足不可伪造性，即原始签名人可以成功伪造代理签名人的代理签名。为此，提出了改进的定向代理签名方案，该方案具有不可伪造性，从而有效地防止原始签名人对代理签名人进行恶意攻击，并将其推广到代理多签名方案中。

An ImprovedDesignated-Receiver Proxy Signature Scheme

In ordinary proxy signature schemes,everyone can verify the validity of proxy signature.While in a designated-receiver signature scheme,to avoid the misuse of proxy signatures,an original signer nominates a person as the signature receiver.As a result,only the person nominated can verify and accept the signature after the proxy signer generating a valid proxy signature on behalf of the original signer.In this paper,we show the designated-receiver proxy signature scheme in Dai et al.is insecure against the original signer's forgery.That is,their scheme does not satisfy the unforgeability property,which is a desired security requirement of a proxy signature scheme.In addition,we present a modified designated-receiver proxy signature scheme with unforgeability,which will efficiently prevent an original signer from malicious attacks.Then we extend the proposed idea into proxy multi-signature scheme.