Beginning with the work of Groth and Sahai, there has been much interest in transforming pairing-based schemes in composite-order groups to equivalent ones in prime-order groups. A method for achieving such transformations has recently been proposed by Freeman, who identified two properties of pairings using composite-order groups — “cancelling” and “projecting” — on which many schemes rely, an...

A group signature allow any member of a group to sign on behalf of the group. A group blind signature requires that a group member signs on group’s behalf a document without knowing its content. In this paper we propose a practical coalition-resistant group blind signature scheme based on the strong RSA and the decisional Diffie-Hellman assumptions. Our scheme is an extension of the group signa...

Randomizable encryption allows anyone to transform a ciphertext into a fresh ciphertext of the same message. Analogously, a randomizable signature can be transformed into a new signature on the same message. We combine randomizable encryption and signatures to a new primitive as follows: given a signature on a ciphertext, anyone, knowing neither the signing key nor the encrypted message, can ra...

In this paper, we review the electronic voting protocols based on blind signature scheme. These protocols try to fulfil the following electronic voting requirements: eligibility, privacy, receipt-freeness, fairness, accuracy, individual verifiability and universal verifiability. Some of them like eligibility and privacy are easily achieved by the nature of blind signatures; on the other hand, s...

Blind digital signatures were introduced by Chaum. In this paper, we show how security and blindness properties for blind digital signatures, can be simultaneously de ned and satis ed, assuming an arbitrary one-way trapdoor permutation family. Thus, this paper presents the rst complexity-based proof of security for blind signatures.

A signature scheme is called structure-preserving if its verification keys, messages, and sig-natures are group elements and the verification predicate is a conjunction of pairing productequations. We answer to the open problem of constructing a constant-size structure-preservingsignature scheme. The security is proven in the standard model based on a novel non-interactiveas...

The concept of partially blind signatures was first introduced by Abe and Fujisaki. Subsequently, in work by Abe and Okamoto, a provably secure construction was proposed along with a formalised definition for partially blind schemes. The construction was based on a witness indistinguishable protocol described by Cramer et al. and utilises a blind Schnorr signature scheme. This paper investigate...

Known constructions of blind signature schemes suffer from at least one of the following limitations: (1) rely on parties having access to a common reference string or a random oracle, (2) are not roundoptimal, or (3) are prohibitively expensive. In this work, we construct the first blind-signature scheme that does not suffer from any of these limitations. In other words, besides being round op...

All previously proposed threshold proxy signature schemes have been based on discrete logarithms required for a protocol to generate and verify a shared secret among the proxy group. Therefore, it is necessary for the proxy signers to perform many expensive modular exponential computations and communications to obtain and verify a shared secret. Moreover, most of the existing threshold proxy si...

In this paper a new patch-based digital signature (DS) is proposed. The proposed approach similar to steganography methods hides the secure message in a host image. However, it uses a patch-based key to encode/decode the data like cryptography approaches. Both the host image and key patches are randomly initialized. The proposed approach consists of encoding and decoding algorithms. The encodin...