抗签名密钥泄露的可撤销无证书签名

当用户的私钥泄露或使用权限到期时,系统如何撤销该用户是亟待解决的问题.这一问题在传统公钥系统TPKC和基于身份的公钥系统IBC下已有解决方案,然而在无证书公钥系统中,这一问题至今没有得到很好的解决.我们知道,无证书公钥系统没有庞杂的证书库和密钥托管问题,只是算法的计算量稍有增加,是TPKC和IBC之外的一种较理想的公钥系统,所以对它的撤销机制的研究十分必要.设计了一种可撤销的无证书签名方案,基本原理是:系统定期地给每个未被撤销的用户生成新的时间密钥,并通过公共信道传输给用户.相比现有的Al-Riyami和Paterson的撤销机制而言,该方案更加高效.同时,新方案达到了抗签名密钥泄露的安全性,且签名密钥的长度非常短.在CDH困难性假设下,该方案是UF-CMA可证明安全的.

Efficient Revocable Certificateless Signature Against Signing Key Exposure

A necessary problem in public key cryptosystem is how to revoke a user when the user's private key is compromised or the permission is prohibited. There have been many effective solutions in both traditional public key cryptosystem(TPKC) and identity based cryptosystem(IBC). But, in certificateless public key cryptosystem the revocation problem still remains to be efficiently solved. As is known, certificateless cryptosystem is a good substitution for TPKC and IBC since it features no certificate and no key escrow with only a little more computation. So, it is very necessary to design efficient revocation solutions in the certificateless setting. This paper gives a revocable certificateless signature scheme in which the system periodically generates new time keys for all non-revoked users via public channels. Compared with the existing Al-Riyami and Paterson revocation mechanism, our scheme is much better in efficiency. Furthermore, the new scheme can resist signing key exposure with very short signing key. In the CDH assumption, our scheme is UF-CMA provably secure.