A revocable certificateless encryption scheme with high performance

Certificateless public key cryptography (CL-PKC) can solve the problems of certificate management in a public key infrastructure (PKI) and of key escrows in identity-based public key cryptography (ID-PKC). In CL-PKC, the key generation center (KGC) does not know the private keys of all users, and their public keys need not be certificated by certification authority (CA). At present, however, most certificateless encryption schemes are based on large integer factorization and discrete logarithms that are not secure in a quantum environment and the computation complexity is high. To solve these problems, we propose a new certificate-less encryption scheme based on lattices, more precisely, using the hardness of the learning with errors (LWE) problem. Compared with schemes based on large integer factorization and discrete logarithms, the most operations are matrixvector multiplication and inner products in our scheme, our approach has lower computation complexity. Our scheme can be proven to be indistinguishability chosen ciphertext attacks (IND-CPA) secure in the random oracle model.

Certificateless public key cryptography (CL-PKC) is an important type of public key cryptography, which effectively solves the inherent key escrow problem in identity based public key cryptography while keeps its certificate-free property. As the adversarial models in CL-PKC are relatively complex, designing efficient and secure certificate less encryption schemes in the standard model has been an interesting and challenging research topic. In this paper, we give cryptanalysis to an existing certificate less encryption scheme in the standard model. We show its insecurity by demonstrating two kinds of attacks.

Ring signature is a kind of digital signature which can protect the identity of the signer. Certificateless public key cryptography not only overcomes key escrow problem but also does not lose some advantages of identity‐based cryptography. Certificateless ring signature integrates ring signature with certificateless public key cryptography. In this paper, we propose an efficient certificateless ring signature; it has only three bilinear pairing operations in the verify algorithm. The scheme is proved to be unforgeable in the random oracle model.

Deniable authentication allows a receiver to identify the source of a given message, but cannot prove the source of a given message to any third party. It can be employed in electronic voting (e-voting) systems, electronic tendering (e-tendering) systems and secure networks negotiation. These applications can be well realised in ad hoc networks. Therefore, deniable authentication is an essential security requirement for ad hoc networks. Aggregate deniable authentication is a method for combining n authenticator of n distinct messages from n distinct users into one single authenticator. This feature is very attractive in bandwidth-limited ad hoc networks. In this paper, we present an efficient certificateless aggregate deniable authentication protocol. Our protocol is based on certificateless public key cryptography that has neither the public key certificates management problem in traditional public key infrastructure (PKI) cryptography nor the key escrow problem in identity-based cryptography. The security of our protocol can be proven in the random oracle model under the bilinear Diffie-Hellman (BDH) and computational Diffie-Hellman (CDH) problems. In addition, our protocol adopts aggregate verification that can speed up the verification of authenticators. Our protocol is very suitable for ad hoc networks.

The rapid proliferation of the Internet of Things (IoT) leaves terminal devices vulnerable to considerable security challenges, notably the absence of robust yet efficient identity authentication mechanisms. Traditional certificate-based approaches incur substantial management overhead and storage expenditure, whereas Identity-Based Cryptography poses inherent key escrow risks. To tackle these challenges, this paper proposes a PUF and SM2-based certificateless identity authentication mechanism that integrates SM2 Certificateless Public Key Cryptography (a Chinese national cryptographic standard) with Physical Unclonable Functions (PUFs). Initially, the proposed solution utilizes PUF technology to derive a unique hardware-generated “fingerprint” from an IoT device, which functions as a root key to generate a partial user private key. This approach essentially binds the terminal’s identity to its physical hardware, thereby effectively mitigating physical cloning attacks against nodes. Moreover, through the adoption of a Certificateless Public Key Cryptography (CLPKC) framework, the complete user private key is jointly generated by a semi-trusted Key Generation Centre (KGC) and the terminal device itself. The comprehensive security analysis proves that the proposed scheme is provably secure under the random oracle model, capable of resisting various common attacks such as physical cloning, man-in-the-middle, and replay attacks. Performance evaluation confirms that the implemented PUF + SM2 certificateless mechanism significantly reduces the size of user public key identifiers to within 64 bytes, offering a substantial advantage over the 1–2 KB certificates typically required in conventional PKI/CA systems, thereby enhancing efficiency in storage and communication.

Certificateless public key cryptography is a new paradigm introduced by AI-Riyami and Paterson. It eliminates the need of the certificates in traditional public key cryptosystems and the key escrow problem in Identity-based Public Key Cryptography (ID-PKC). Due to the advantages of the certificateless public key cryptography, we propose a novel certificateless blind signature scheme based on pairings in the paper. Firstly, we give formal security definitions of blindness and unforgeability in our scheme. Then an concrete instance is given and we show that the proposed scheme is provably secure in the random oracle model. The security of our schemes is proven based on the hardness of computational Diffie-Hellman problem and the bilinear pairing inversion Problem (BPI). Finally, by comparing our scheme with Zhang's scheme in terms of computational cost and the signature size, we show that our scheme is more efficient, since no pairing computation is required in the signing, and only one pairing computation is required in the verifying phase.

Based on mobile devices limitations, several user authentications and key exchange schemes have been proposed for mobile devices using identity-based public key cryptography (ID-PKC). However, these schemes suffer from key escrow problem. Moreover, they are not secure against impersonation attacks, and they can’t achieve perfect forward secrecy. In this paper, a new user authentication and key exchange protocol for the mobile client-server environment is proposed. Certificateless public key cryptography (CL-PKC) and bilinear pairing are adopted in the proposed scheme. Our protocol solves the key escrow problem of identity-based public key cryptography. Also, it is secure against both adversaries type I and type II. Furthermore, the proposed protocol achieves perfect forward secrecy. We prove the security of our protocol in the random oracle model under the Computational Diffie-Hellman (CDH) problem. Hence, the proposed scheme is more suitable for the mobile devices environments.

Certificateless multi-proxy signature

Certificateless cryptography (CL-PKC) is a concept that aims at enjoying the advantages of identity based cryptography without suffering from its inherent key escrow. Several methods were recently suggested to generically construct a certificateless encryption (CLE) scheme by combining identity based schemes with ordinary public key cryptosystems. Whilst the security of one of these generic compositions was proved in a relaxed security model, we show that all them are insecure against chosen-ciphertext attacks in the strongest model of Al-Riyami and Paterson. We show how to easily fix these problems and give a method to achieve generic CLE constructions which are provably CCA-secure in the random oracle model. We finally propose a new efficient pairing-based scheme that performs better than previous proposals without pre-computation. We also prove its security in the random oracle model.

Certificateless threshold signature scheme from bilinear maps

Tampering, forgery and theft of the measurement and control messages in a smart grid could cause one breakdown in the power system. However, no security measures are employed for communications in intelligent substations. Communication services in an intelligent substation have high demands for real-time performance, which must be considered when deploying security measures. This paper studies the security requirements of communication services in intelligent substations, analyzes the security capabilities and shortages of IEC 62351, and proposes a novel security scheme for intelligent substation communications. This security scheme covers internal and telecontrol communications, in which the real-time performance of each security measure is considered. In this scheme, certificateless public key cryptography (CLPKC) is used to avoid the latency of certificate exchange in certificate-based cryptosystem and the problem of key escrow in identity-based cryptosystem; the security measures of generic object-oriented substation event, sampled measure value and manufacturing message specification in IEC 62351 are improved to meet the real-time requirements of the messages as well as to provide new security features to resist repudiation and replay attacks; and the security at transport layer is modified to fit CLPKC, which implements mutual authentication by exchanging signatures. Furthermore, a deployment of CLPKC in an intelligent substation is presented. We also evaluate the security properties of the scheme and analyze the end-to-end delays of secured services by combining theoretical calculation and simulation in this paper. The results indicate that the proposed scheme meets the requirements of security and real-time performance of communications in intelligent substations.

Support of membership revocation is a desirable functionality for any group signature scheme. Among the known revocation approaches, verifier-local revocation (VLR) seems to be the most flexible one, because it only requires the verifiers to possess some up-to-date revocation information, but not the signers. All of the contemporary VLR group signatures operate in the bilinear map setting, and all of them will be insecure once quantum computers become a reality. In this work, we introduce the first lattice-based VLR group signature, and thus, the first such scheme that is believed to be quantum-resistant. In comparison with existing lattice-based group signatures, our scheme has several noticeable advantages: support of membership revocation, logarithmic-size signatures, and weaker security assumption. In the random oracle model, our scheme is proved to be secure based on the hardness of the $\mathsf{SIVP}_{\widetilde{\mathcal{O}}(n^{1.5})}$ problem in general lattices - an assumption that is as weak as those of state-of-the-art lattice-based standard signatures. Moreover, our construction works without relying on encryption schemes, which is an intriguing feature for group signatures.

New chosen-ciphertext secure identity-based encryption with tight security reduction to the bilinear Diffie–Hellman problem

Due to avoiding the inherent escrow of identity-based cryptography and yet not requiring certificates to guarantee the authenticity of public keys, certificateless public key cryptography has received a significant attention. Due to various applications of bilinear pairings in cryptography, numerous pairing-based encryption schemes, signature schemes, and other cryptographic primitives have been proposed. In this paper, a new certificateless signature scheme based on bilinear pairings is presented. The signing algorithm of the proposed scheme is very simple and does not require any pairing computation. Combining our signature scheme with certificateless public key cryptography yields a complete solution of certificateless public key system. As an application of the proposed signature scheme, a certificateless proxy signature scheme is also presented. We analyze both schemes from security point of view.

Liskov proposed several weakened versions of the random oracle model, called weakened random oracle models (WROMs), to capture the vulnerability of ideal compression functions, which are expected to have the standard security of hash functions, i.e., collision resistance, second-preimage resistance, and one-wayness properties. The WROMs offer additional oracles to break such properties of the random oracle. In this paper, we investigate whether public-key encryption schemes in the random oracle model essentially require the standard security of hash functions by the WROMs. In particular, we deal with four WROMs associated with the standard security of hash functions; the standard, collision tractable, second-preimage tractable, first-preimage tractable ones (ROM, CT-ROM, SPT-ROM, and FPT-ROM, respectively), done by Numayama et al. for digital signature schemes in the WROMs. We obtain the following results: (1) The OAEP is secure in all the four models. (2) The encryption schemes obtained by the Fujisaki-Okamoto conversion (FO) are secure in the SPT-ROM. However, some encryption schemes with FO are insecure in the FPT-ROM. (3) We consider two artificial variants wFO and dFO of FO for separation of the WROMs in the context of encryption schemes. The encryption schemes with wFO (dFO, respectively) are secure in the CT-ROM (ROM, respectively). However, some encryption schemes obtained by wFO (dFO, respectively) are insecure in the SPT-ROM (CT-ROM, respectively). These results imply that standard encryption schemes such as the OAEP and FO-based one do not always require the standard security of hash functions. Moreover, in order to make our security proofs complete, we construct an efficient sampling algorithm for the binomial distribution with exponentially large parameters, which was left open in Numayama et al.’s paper.