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 chosenmessage 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.

In 2012, Tseng and Tsai presented a novel revocable ID (identity)-based public key setting that provides an efficient revocation mechanism with a public channel to revoke misbehaving or compromised users from public key systems. Subsequently, based on Tseng and Tsai's revocable ID-based public key setting, Tsai et al. proposed a new revocable ID-based signature (RIBS) scheme in the standard model (without random oracles). However, their RIBS scheme possesses only existential unforgeability under adaptive chosen-message attacks. In the article, we propose the first strongly secure RIBS scheme without random oracles under the computational Diffie-Hellman and collision resistant assumptions. Comparisons with previously proposed schemes are made to demonstrate the advantages of our scheme in terms of revocable functionality and security property.

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 chosenmessage 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.

In the past, many ID-based signature (IBS) schemes based on the integer factorization or discrete logarithm problems were proposed. With the progress on the development of quantum technology, IBS schemes mentioned above would become vulnerable. Recently, several IBS schemes over lattices were proposed to be secure against attacks in the quantum era. As conventional public-key settings, ID-based public-key settings have to offer a revocation mechanism to revoke misbehaving or malicious users. However, in the past, little work focuses on the revocation problem in the IBS schemes over lattices. In this article, we propose a new revocable IBS (RIBS) scheme with short size over lattices. Based on the short integer solution (SIS) assumption, we prove that the proposed RIBS scheme provides existential unforgeability against adaptive chosen-message attacks. As compared to the existing IBS schemes over lattices, our RIBS scheme has better performance in terms of signature size, signing key size, and the revocation mechanism with public channels.