A blind signature scheme is a cryptographic protocol to obtain a valid signature for a message from a signer such that signer’s view of the protocol can’t be linked to the resulting message signature pair. This paper presents blind signature scheme using Chebyshev polynomials. The security of the given scheme depends upon the intractability of the integer factorization problem and discrete loga...

This paper shows some efficient and provably-secure convertible undeniable signature schemes (with both selective conversion and all conversion), in the standard model and discrete logarithm setting. They further satisfy unambiguity, which is traditionally required for anonymous signatures. Briefly, unambiguity means that it is hard to generate a (message, signature) pair which is valid for two...

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...

Blind signature schemes provide the functionality of a carbon copy envelope: The user (receiver) puts his message into this envelope and hands it over to the signer (sender). The signer in return signs the envelope and gives it back to the user who recovers the original signed message out of the envelope. Security says that the signer remains oblivious about the message (blindness), but at the ...

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 ...

Blind signatures have been widely adopted to construct untraceable electronic cash systems since they are both unlinkable and unforgeable. Although unlinkability protects the privacy of customers and users, it may be abused by criminals for such purposes as to launder money or to safely get a ransom. The techniques of fair blind signatures are developed to deal with the abuse of unlinkability. ...