Verifiable threshold signature schemes against conspiracy attack

In this study, the author has designed new verifiable (t,n) threshold untraceable signature schemes. The proposed schemes have the following properties:(1) Verification: The shadows of the secret distributed by the trusted center can be verified by all of the participants;(2) Security: Even if the number of the dishonest member is over the value of the threshold, they cannot get the system secret parameters ,such as the group secret key, and forge other member's individual signature;(3) Efficient verification: The verifier can verify the group signature easily and the verification time of the group signature is equivalent to that of an individual signature; (4) Untraceability: The signers of the group signature cannot be traced.     

A novel group signature with one time secret key

INTRODUCTION The concept of group signature, first introduced by Chaum and van Heyst (1992), allows each group member to sign messages on behalf of the group, and the receiver can use a group public key to verify the group signature, but cannot reveal the signer. In case of disputes, the group authority can open the group signature and identify the signer, but the outsider cannot identify all previous group signatures gener-ated by the same group member. A group member cannot impersonate…     

Colluding attacks on a group signature scheme

INTRODUCTION The concept of group signature,first introduced by Chaum and van Heyst(1992),allows each group member(and only the group member)to sign mes-sages on behalf of the group,and requires that the receiver can use a group public key to verify the group signature,but cannot reveal the signer.The group signature should be traceable,i.e.the group authority can open the group signature and identify the signer.The outsider cannot identify all previous group sig-natures generated by the …     

Self-certified multi-proxy signature schemes with message recovery

Multi-proxy signature schemes allow the original signer to delegate his/her signing power to n proxy signers such that all proxy signers must corporately generate a valid proxy signature on behalf of the original signer. We first propose a multi-proxy signature scheme based on discrete logarithms and then adapt it to the elliptic curve cryptosystem. With the integration of self-certified public-key systems and the message recovery signature schemes, our proposed schemes have the following advantages： （1） They do not require the signing message to be transmitted, since the verifier can recover it from the signature; （2） The authentication of the public keys, verification of the signature, and recovery of the message can be simultaneously carried out in a single logical step; （3） No certificate is needed for validating the public keys. Further, the elliptic curve variant with short key lengths especially suits the cryptographic applications with limited computing power and storage space, e.g., smart cards. As compared with the previous work that was implemented with the certificate-based public-key systems, the proposed schemes give better performance in terms of communication bandwidth and computation efforts.     

Non-interactive identity-based threshold signature scheme without random oracles

A （t, n） threshold signature scheme distributes the secret key and hence the signing ability to n players in a way that any set of t＋ 1 or more honest players can collaborate to sign, while any set of t players cannot. In this paper we propose an identity-based threshold signature （IBTHS） scheme from bilinear pairings. The signing phase of our scheme is non-interactive, meaning that the signing players do not need to talk to each other. We prove our scheme secure （i.e., unforgeable and robust） in the standard model （i.e., without random oracles）. No earlier proposed IBTHS scheme achieved even one of the features of being non-interactive （in the signing phase） and secure in the standard model.     

对一种新型代理签名方案分析与改进之评论

2006年鲁荣波在其博士论文＂代理数字签名和群数字签名的分析与设计＂中对一种新型代理签名方案进行了分析与改进,该方案改进自谷利泽等人于2005年所提出的代理签名方案,鲁氏强化了谷氏在不可伪造性上的弱点,并且回避了孤悬因子所产生的弱点安全问题。然而鲁氏在改进的方案中,误用参数及给了错误的计算方法,因此在推导的过程也就得到错误的结果。本论文指出错误之处,并给出正确算法,使其理论完善。     

对RSA密码系统旁路攻击的防御

Based on the structure of the side channel attacks (SCAs) to RSA cryptosystem can resist the fault attack andcombine with the randomization method for the message and secret exponent, a new implementation scheme of CRT-based(the Chinese remained theorem) RSA is proposed. The proposed scheme can prevent simple power analysis (SPA), differentialpower analysis (DPA) and time attack, and is compatible with the existing RSA-CRT cryptosystem as well. In addition, animprovement for resisting fault attack is proposed, which can reduce extra computation time.     

一个群签名方案的安全性分析

对一个改进的基于中国剩余定理的群签名方案进行安全性分析,指出方案不可抵御伪造攻击,群中心或群中成员即使不知道其他成员的签名密钥也可伪造其签名;同时指出验证者在验证签名有效性的同时也可以判断出签名者,不满足群签名的性质,因此不是一个真正意义上的群签名.