Concurrent executions of a zero-knowledge protocol by a single prover (with one or more verifiers) may leak information and may not be zero-knowledge in toto. In this article, we study the problem of maintaining zero-knowledge.We introduce the notion of an (α, β) timing constraint: for any two processors P1 and P2, if P1 measures α elapsed time on its local clock and P2 measures β elapsed time on its local clock, and P2 starts afterP1 does, then P2 will finish after P1 does. We show that if the adversary is constrained by an (α, β) assumption then there exist four-round almost concurrent zero-knowledge interactive proofs and perfect concurrent zero-knowledge arguments for every language in NP. We also address the more specific problem of Deniable Authentication, for which we propose several particularly efficient solutions. Deniable Authentication is of independent interest, even in the sequential case; our concurrent solutions yield sequential solutions without recourse to timing, that is, in the standard model.

Concurrent Zero-Knowledge.

Security for 4G and 5G cellular networks

This paper presents fingerprint biometric-based self-authentication and deniable authentication schemes, which enable a receiver to identify source of the message but not to prove the identity of the sender to a third party. At first, we identify the security flaws of some recently proposed deniable authentication schemes by three application scenarios, and prove that those schemes are vulnerable to impersonation and eavesdropping attacks. For remedy, we propose two-factor-based self-authentication and deniable authentication schemes in which, firstly, each user has to perform self-authentication by something he knows (password) and something he is (biometrics), and then he can accomplish the transaction, e.g., e-commerce. Security analysis shows that the proposed schemes can overcome the security pitfalls of the previous schemes and are secure, reliable and practicable with high potential to be used in the electronic world.

Fingerprint Biometric-based Self-Authentication and Deniable Authentication Schemes for the Electronic World

Recently, Shen et al. proposed an improvement to Hwang-Li's scheme to prevent from forgery attack. However, Leung et al. pointed out that this improved scheme is still susceptible to forgery attack proposed by Chan and Cheng. Accordingly, the current paper presents an enhancement based on generalized ElGamal signature scheme to resolve such problems. As a result, the proposed scheme enables users to update their passwords freely without the help of a remote system, while also providing mutual authentication. In addition, the computational costs of this scheme are less than those of previously proposed schemes.

Zuhua Shao

Papers

Efficient deniable authentication protocol based on generalized ElGamal signature scheme

Improvement of threshold proxy signature scheme

Improvement of digital signature with message recovery and its variants based on elliptic curve discrete logarithm problem

Security of robust generalized MQV key agreement protocol without using one-way hash functions