In this paper,we first proposed a new concurrent signature based on a verifiable ring signature scheme and constructed a corresponding concurrent signature protocol.At last,we gave the analysis of the security of our scheme.The advantages of concurrent signature scheme is very sufficient to fairness as well as signer-ambiguity,unforgeriability and verifiability.It provides a new way to solve the problem of fair exchange of signatures.
In this paper,we first proposed a new concurrent signature based on a verifiable ring signature scheme and constructed a corresponding concurrent signature protocol.At last,we gave the analysis of the security of our scheme.The advantages of concurrent signature scheme is very sufficient to fairness as well as signer-ambiguity,unforgeriability and verifiability.It provides a new way to solve the problem of fair exchange of signatures.
At first, an convertible ID-based two-party ring signature scheme is designed, in such a scheme, after releasing of a converting information by the real signer, a ring signature can be transformed into a standard signature which can be verified publicly. And then, based on this ring signature, a convertible perfect concurrent signature protocol is proposed. Different from a general concurrent signature, there is an extra procedure called “ACONVERT” in this protocol, which can transform the exchanged ring signature into a common form, so it realizes the fair exchange of signature. At last, the security of the protocol is analyzed.
Through analysis, we point out Luo et al.’s and Sun et al.’s signcryption-based concurrent signature schemes have the same defect in ambiguity and therefore the fair exchange protocols based on their schemes are not fair. Thus based on the notions of signcryption and concurrent signature, a new signcryption-based concurrent signature scheme from bilinear pairing is presented, and based on this scheme, a new fair exchange protocol is proposed. Since we adopt a new method to construct the new signcryption-based concurrent signature scheme, the new scheme redresses the flaw of Luo et al.’s and Sun et al.’s schemes, and the fair exchange protocol based on the new scheme is also fair. Besides, due to the new scheme’s independence of the ring signature and simplification of encryption operations, the new scheme has the advantage of short signatures and low computation cost. We improve Luo et al.’s definition of the security model of a signcryption-based concurrent signature scheme and prove the proposed scheme and protocol are secure under the computational Diffie-Hellman assumption in the random oracle model.
We propose a fair novel concurrent signature scheme. It resolves the existing problems in traditional concurrent signature schemes, that is initial signer (A) has some advantages over matching signer (B), such as A could show B's ambiguous signature and the keystone to a third party in private to demonstrate B's binding signature but B can not, or A could keep the keystone secret and B do not have power to force A to release it. In our scheme, the keystones were produced by both A and B, that is to say, the two participants in our scheme have equal positions, no one has any priority than the other, so our scheme can achieve the fairness of both sides.
Concurrent signatures scheme is an effective way to solve the problem of fair exchange without the help of any trusted third party. Until now, all concurrent signatures are based on traditional cryptosystems, but the emergence of quantum computing poses a severe threat to the security of classic public–key cryptosystems. More and more attentions are being paid to lattice–based cryptosystems, which is one of the candidate cryptosystems against the attacks from quantum computing. In this paper, we present a new formal model of multi–party concurrent signatures scheme and a lattice–based multi–party concurrent signatures scheme. The scheme has comparative advantages in both efficiency and security over the existing concurrent signatures schemes based on traditional cryptosystem. In particular, our scheme is constructed based on constant–size ring signatures, and thus we have solved the open problem: how to construct a multi–party concurrent signatures scheme based on constant–size ring signatures, which was proposed by Tonien et al. (2006).
When using digital signatures, we need to deal with the problem of fairness of information exchange. To solve this problem, Chen, etc. introduced a new conception which is named concurrent signatures in Eurocrypt'04. Using concurrent signatures scheme, two entities in the scheme can generate two ambiguous signatures until one of the entities releases additional information which is called keystone. After the keystone is released, the two ambiguous signatures will be bound to their real signers at the same time. In order to provide a method to solve the fairness problem of quantum digital signatures, we propose a new quantum concurrent signature scheme. The scheme we proposed does not use a trusted third party in a quantum computing environment, and has such advantages as no need to conduct complex quantum operations and easy to implement by a quantum circuit. Quantum concurrent signature improves the theory of quantum cryptography, and it also provides broad prospects for the specific applications of quantum cryptography.
Concurrent Signatures scheme is an effective way to solve the problem of fair exchange without the help of any trusted third party, it has the advantage of efficiency. Until now, all concurrent signatures are based on traditional cryptosystems, but the emergence of quantum computing poses a severe threat to the security of classic public-key cryptosystems. More and more attentions are being paid to lattice-based cryptosystems, which is one of the candidate cryptosystems against the attacks from quantum computing. In this paper we present a new formal model of multi-party concurrent signatures scheme which is constructed based on constant-size ring signatures, and a lattice-based multi-party concurrent signatures scheme. The scheme has comparative advantages in both efficiency and security over the existing concurrent signatures schemes based on traditional cryptosystems. In particular, our scheme is constructed based on constant-size ring signatures, and thus we have solved the open problem: how to construct a multi-party concurrent signatures scheme based on constant-size ring signatures, which was proposed by Dongvu Tonien, Willy Susilo and Reihaneh Safavi-Naini in 2006.