Informatica

The primitive of certificateless signature, since its invention, has become a widely studied paradigm due to the lack of key escrow problem and certificate management problem. However, this primitive cannot resist catastrophic damage caused by key exposure. Therefore, it is necessary to integrate revocation mechanism into certificateless signature. In this paper, we propose a new certificateless signature scheme with revocation (RCLS) and prove its security under the standard model. In the meanwhile, our scheme can resist malicious-but-passive Key Generation Center (KGC) attacks that were not possible in previous solutions. The theoretical analysis shows our scheme has high efficiency and practicality.

This paper studies the generic construction of certificate-based signature (CBS) from certificateless signature (CLS). This paper proposes a new generic conversion from CLS to CBS which is more intuitive, simpler, and provably secure without random oracles than the current one. To develop the security proof, we put forth one novel CLS security model which features a previously neglected but nontrivial attack and hence captures the CLS security notion more comprehensively. We show that many existing CLS schemes can be proved secure in the current model by slightly modifying its original security proof. Following this conversion, many provably secure CBS schemes can be constructed from the corresponding existing CLS schemes.

Certificateless short signature (CLSS) possesses the advantages of both certificateless signature and short signature. CLSS eliminates the certificate management in conventional signatures and solves the key escrow problem in ID-based signatures. In the meantime, due to its short signature length, CLSS reduces the bandwidth for communication so that it is suitable for some specific authentication applications requiring bandwidth-constrained communication environments. However, up to now, there is no work on studying the revocation problem in existing CLSS schemes. In this article, we address the revocation problem and propose the first revocable certificateless short signature (RCLSS) scheme. Based on the computational Diffie–Hellman (CDH) assumption, we demonstrate that our RCLSS scheme possesses strong unforgeability against adaptive chosen-message attacks under an accredited security model. It turns out that our scheme has the shortest signature length while retaining computational efficiency. Thus, the proposed RCLSS scheme is well suited for low-bandwidth communication environments. Finally, we combine the proposed RCLSS scheme with cloud revocation authority (CRA) to present a CRA-aided authentication scheme with period-limited privileges for mobile multi-server environment.

Up to date, a large number of ID-based signature (IBS) schemes based on bilinear pairings have been proposed. Most of these IBS schemes possess existential unforgeability under adaptive chosen-message attacks, among which some offer strong unforgeability. An IBS scheme is said to be strongly unforgeable if it possesses existential unforgeability and an adversary who is given signatures of the IBS scheme on some message m is unable to generate a new signature on m. Strong unforgeable IBS schemes can be used to construct many important ID-based cryptographic schemes. However, the existing strongly unforgeable IBS schemes lack efficiency for the signature size and the computation cost of verification phase. In this paper, we propose an efficient strongly unforgeable IBS scheme without random oracles. Under the computational Diffie–Hellman and collision resistant hash assumptions, we demonstrate that the proposed IBS scheme possesses strong unforgeability against adaptive chosen-message attacks. When compared with previously proposed strongly unforgeable IBS schemes, our scheme has better performance in terms of signature size and computation cost.

We propose an Identity Based Strong Designated Verifier Signature (IBSDVS) scheme using bilinear pairings. Designated Verifier Signature finds application in e-voting, auctions and call for tenders. We prove that the scheme is secure against existential forgery under adaptively chosen message and identity attack in random oracle model. We also show that the problem of delegatability does not exist in our scheme.