A (t, n) threshold signature scheme allows t or more group members to generate signatures on behalf of a group with n members, while any t−1 or less members cannot do the same thing. In 2001, based on a variant of ElGamal digital signature scheme, Li et al. proposed two (t, n) threshold signature schemes with traceable signers. One of their schemes needs the assistance of a mutually trusted cen...

A fair blind signature scheme allows the trustee to revoke blindness so that it provides authenticity and anonymity to honest users while preventing malicious users from abusing the anonymity to conduct blackmail etc. Although plausible constructions that offer efficient tricks for anonymity revocation have been published, security, especially one-more unforgeability and revocability against ad...

In 2005, Lee et al. proposed a blind signature scheme based on the discrete-logarithm problem to achieve the untraceability or unlinkability property. However, the scheme will be demonstrated as not being secure in this manuscript. We design an attack on the scheme such that a signature requester can obtain more than one valid signatures by performing only one round of the protocol. It violates...

In the paper, we analyze two signature schemes. The first is a (tj , t, n) threshold group signature scheme proposed by Shi and Feng in [1]. The second is a fair blind signature scheme proposed by Feng in [2]. Our results show that both schemes are forgeable. Besides, we introduce a concept, i.e., suspended factor, to describe the common error in designing signature scheme, which means that som...

One important requirement of electronic cash systems is the anonymity of customers. Unconditional anonymity is also very well suited to support criminals in blackmailing. Maitland and Boyd proposed at ICICS 2001 an offline electronic cash system based on a group signature scheme. Their scheme cannot be used to solve blackmailing and other anonymity problems such as money laundering and illegal ...

In a blind signature scheme, the user can get a signature sig(m) on message m generated from the signer’s blind signature sig(m) on blinded message m, but the signer can’t know the contents of the message m. When the signature sig(m) is revealed to public after that have been signed, if the signer can find the linkage between the signature sig(m) and the blind signature sig(m) on blinded messag...

In this paper, we propose a provably secure group-oriented blind (t, n) threshold signature scheme, which is the first scheme whose security is proved to be equivalent to the discrete logarithm problem in the random oracle model. Based on the scheme, any t out of n signers in a group can represent the group in signing blind threshold signatures, which can be used in anonymous digital e-cash sys...

Proxy blind Signature allows an original signer to delegate his/her signing capability to a proxy signer who performs message signing blindly on behalf of original signer but he cannot make any link between the blind signature and the identity of the message's owner. Using bilinear pairings, so many ID-based proxy blind signature (IDPBS) schemes have been proposed. But the computation cost of a...

Multivariate Cryptography is one of the main candidates for creating post-quantum cryptosystems. Especially in the area of digital signatures, there exist many practical and secure multivariate schemes. However, there is a lack of multivariate signature schemes with special properties such as blind, ring and group signatures. In this paper, we propose a technique to transform the Rainbow multiv...