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.

Certificateless public-key systems (CL-PKS) were introduced to simultaneously solve two critical problems in public-key systems. One is the key escrow problem in ID-based public-key systems and the other is to eliminate the presence of certificates in conventional public-key systems. In the last decade, several certificateless signature (CLS) schemes have been proposed in the random oracle model. These CLS schemes possess existential unforgeability against adaptive chosen-message attacks, and only few of them possess strong unforgeability. A CLS scheme with strong unforgeability plays an important role in the construction of certificateless cryptographic schemes. Unfortunately, all the existing CLS schemes in the standard model (without random oracles) have been shown insecure to provide existential unforgeability under a generally adopted security model. In the article, we propose a strongly secure CLS scheme in the standard model under the generally adopted security model. Our scheme possesses not only existential unforgeability but also strong unforgeability, and turns out to be the first strongly secure CLS scheme in the standard model. Under the collision resistant hash (CRH) and computational Diffie–Hellman (CDH) assumptions, we prove that our CLS scheme possesses strong unforgeability against both Type I (outsiders) and Type II (key generation center) adversaries.