Existing directed proxy signature schemes have the problems of certificate management or key escrow because most of them are based on the certificate public key cryptography or the identity-based cryptography. In order to protect the privacy of signature receiver, we propose in this paper a new certificateless directed proxy signature scheme based on the merit of certificateless public key cryptography. In the scheme, the proxy signer can generate a directed proxy signature on behalf of the original signer for a designated receiver, only the designated-receiver specified by the original signer can verify the validity of the signature. Compared with existing directed proxy signature schemes, the new one does not have the problems of certificate management and key escrow, so its security is improved. Analysis shows that the new scheme satisfies all the required characteristics of the directed proxy signature and is suitable for practical application.%已有的定向代理签名方案,大都是基于证书公钥密码体制或基于身份密码体制的,都存在证书管理问题或密钥托管问题.为了保护签名接收人的隐私,基于无证书密码体制的优点,提出一种新的无证书定向代理签名方案.在该方案中,代理签名人可以代理原始签名人生成针对指定接收人的定向代理签名,只有原始签名人指定的接收人才可以验证签名的有效性.相比已有方案,新方案不存在证书管理和密钥托管的问题,安全性得到了提高.分析表明,新方案满足定向代理签名的所有性质,适合于实际应用.
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