The concept of ring signature was introduced by Rivest, Shamir and Tauman. This signature is considered to be a simplified group signature from which identity of signer is ambiguous although verifier knows the group to which signer belong. In this paper we introduce a new proxy ring signature scheme.

Automated signature verification is an important capability when doing fraud detection from high volumes of document images. The challenge is mainly caused by the combination of inherent writer variations and the conscious attention placed by the fraudster on imitating a legitimate signature. Getting good signature references is the first and most important step affecting verification accuracy....

Transitive signature, motivated by signing vertices and edges of a dynamically growing, transitively closed graph, was first proposed by Micali and Rivest. The general designing paradigm proposed there involved a underlying standard signature scheme, which is required to be existentially unforgeable against adaptive chosen message attacks. We show that the requirement for the underlying signatu...

Since the discovery of identity based cryptography, a number of identity based signature schemes were reported in the literature. Although, a lot of identity based signature schemes were proposed, the only identity based deterministic signature scheme was given by Javier Herranz. This signature scheme uses Schnorr signature scheme for generating the private key of the users and uses BLS short s...

A blind signature scheme is a protocol for obtaining a signature from a signer such that the signer's view of the protocol cannot be linked to the resulting message-signature pair. Blind signature schemes are used in anonymous digital payment systems. Since the existing proposals of blind signature schemes provide perfect unlinkability, such payment systems could be misused by criminals, e.g. t...

Directed signature scheme allows only a designated verifier to check the validity of the signature issued to him; and at the time of trouble or if necessary, any third party can verify the signature with the help of the signer or the designated verifier as well. Due to its merits, directed signature scheme is widely used in situations where the receiver’s privacy should be protected. Threshold ...

The study presents a threshold signature scheme. While developing threshold cryptography, the concept of threshold signature can accomplish a tradeoff between efficiency in use and dependability of security. The presented threshold signature scheme can resist conspiracy attack by controlling the right of issuing group signature, and the performance of constructing group signature is also enhanc...

This paper analyzes the security of a very efficient signature scheme proposed by C.H. Tan, X. Yi and C.K. Siew: the TYS signature scheme. We show that this scheme is universally forgeable; more specifically, we show that anyone is able to produce a valid TYS signature on a chosen message from an arbitrary valid message/signature pair. We also suggest modifications to the TYS signature scheme a...

This paper presents two types of digital signature schemes combinely that are blind signature and proxy signature. In the proxy blind signature scheme, a signer other than the original signer signs the document as the agent of the original signer not knowing the meaning of the message. In this paper, an enhanced proxy blind signature is proposed, in which a time stamp approach is added to the p...

Certificateless signature scheme eliminates the need of certificates in the traditional signature scheme and solves the inherent key escrow problem in the identity based signature scheme. In this paper, we propose a new construction of certificateless signature which is strongly unforgeable in the standard model with the computational Diffie-Hellman assumption in bilinear groups. As far as we k...