We propose a model for fair electronic cash issued by multiple banks for the first time. A scheme of electronic cash with multiple banks in which a user can be traced is presented by using the improved group signature scheme of Cam97[4] and the group blind signature scheme of Lys98[16]. A weakness in the design of withdrawal and payment protocols of electronic cash using the existing group sign...

At Crypto’99, Dr Coron, Naccache, and Stern presented a signature forgery strategy of the RSA digital signature scheme. The attack is valid on Chaum’s blind signature scheme, which has been applied to many practical applications such as electronic cash and voting. In this paper we propose a method to inject a randomizing factor into a message when it is signed by the signer in Chaum’s blind sig...

Proxy signature is a signature that an original signer delegates his or her signing capability to a proxy signer, and then the proxy signer creates a signature on behalf of the original signer. However, Sun et al. [7] showed that the proxy and multi-proxy signatures of Lee et al. [3], and the strong proxy signature scheme with proxy signer privacy protection of Shum et al. [6] are not against t...

A proxy blind signature scheme is a digital signature scheme which combines the properties of proxy signature and blind signature schemes. Recently, Tan et al. proposed two proxy blind signature schemes based on DLP and ECDLP respectively. Later, compared with Tan et al.’s scheme, Lal and Awasthi further proposed a more efficient proxy blind signature scheme. In this paper, we show that Tan et ...

David Chaum has introduced the idea of blind signamres, an extension of the concept of digital signatures, as a way to protect the identity and privacy of a user in electronic payment and service networks. Blind signatures also prevent so-called 'dossier creation " about users by organizations. While the concept of blind signatures still allows authorities to distinguish between valid and false...

A blind signature scheme is a protocol for obtaining a digital signature from a signer, but the signer can neither learn the messages he/she sign nor the signatures the recipients obtain afterwards. Partially blind signature is a variant such that part of the message contains pre-agreed information (agreed by the signer and the signature requester) in unblinded form, while threshold blind signa...

In a proxy signature scheme, a potential signer delegates his signing capability to a proxy entity, who signs a message on behalf of the original signer. All the proposals of proxy signature schemes made until now have been based on Schnorr's signature scheme. Threshold versions of these schemes have also been proposed, in which the power of the proxy signer is distributed among a group of play...

Unforgeability and blindness are two important properties of blind signature. The latter means that after interacting with various users, the signer is unable to link a valid message-signature pair. In ICCSA 2006, Zhang et al. showed that a signer in an identity-based blind signature scheme proposed by Huang et al. is able to link a valid messagesignature pair obtained by some user. They also p...

In 2004, Yang et al. proposed an efficient (t, n) threshold proxy signature scheme with known signers. However, Maimani et al. showed that a malicious original signer can forge a valid proxy signature for any message in Yang et al.’s scheme and further proposed an improvement to remedy such an attack. In this paper, we will show that in Maimani et al.s improvement, a malicious original or proxy...

Duc et al. proposed a forward-secure blind signature scheme in [1]. They claimed that the scheme is constructed from the provably secure OkamotoGuilou-Quisquater blind signature scheme. But we recently found that their scheme is insecure. In the paper, we show the scheme is universally forgeable by a simple and direct attack.