Vehicular ad hoc networks (VANETs), which are the backbone of intelligent transportation systems (ITSs), facilitate critical data exchanges between vehicles. This necessitates secure transmission, which requires guarantees of message availability, integrity, source authenticity, and user privacy. Moreover, the traceability of network participants is essential as it deters malicious actors and allows lawful authorities to identify message senders for accountability. This introduces a challenge: balancing privacy with traceability. Conditional privacy-preserving authentication (CPPA) schemes are designed to mitigate this conflict. CPPA schemes utilize cryptographic protocols, including certificate-based schemes, group signatures, identity-based schemes, and certificateless schemes. Due to the critical time constraints in VANETs, efficient batch verification techniques are crucial. Combining certificateless schemes with batch verification leads to certificateless aggregate signature (CLAS) schemes. In this paper, cryptanalysis of Xiong’s CLAS scheme revealed its vulnerabilities to partial key replacement and identity replacement attacks, alongside mathematical errors in the batch verification process. Our proposed CLAS scheme remedies these issues by incorporating an identity authentication module that leverages chameleon hashing within elliptic curve cryptography (CHAM-CLAS). The signature and verification modules are also redesigned to address the identified vulnerabilities in Xiong’s scheme. Additionally, we implemented the small exponents test within the batch verification module to achieve Type III security. While this enhances security, it introduces a slight performance trade-off. Our scheme has been subjected to formal security and performance analyses to ensure robustness.

Blockchain is currently one of the most widely discussed inventions in the information and communication technology industry. It is a pillar of the fourth industrial revolution and it is a cryptographically demanding technology that is regarded as one of the most influential topics in academia. Many blockchain platforms currently utilize third-party cryptographic libraries that offer many cryptographic primitives in order to ensure users' protection against cyber-attacks. The Networking and Cryptography library (NaCl) is an open-source library for cryptographic primitives. NaCl is known to be one of the best libraries that provide usability property. Although NaCl is easy to use and ensures: confidentiality, integrity, and authenticity, it fails to provide the non-repudiation service. In this paper, an improvement to the blockchain platforms is proposed by enhancing the NaCl library to achieve the non-repudiation property that enhances the security level of the implemented blockchain platform. In NaCl, to provide the aforementioned security services, messages are signed and then encrypted. Therefore, the non-repudiation service is not provided. In this paper, the proposed solution is based on adding a signature block to enable a non-repudiation property. First, logical analysis is conducted using the BAN logic on the NaCl library to prove that it does not provide the non-repudiation property. Subsequently, a modification to the library is proposed, and the correctness of the proposed solution is proven using BAN logic. The analysis suggests that the proposed solution fixes the aforementioned problem.

Personal credentials, such as passports and drivers’ licenses, can be implemented electronically using multi-show protocols. In this paper, we introduce an IoT Privacy-Oriented selective disclosure credential system, i.e. based on bilinear pairings and multilinear maps. The proposed system consists of three protocols, which allow users to be in control of their personal credentials. The Credentials Authority (CA) verifies and attests to the users credentials. Once the CA signs these credentials, the users cannot modify any of them. Moreover, the users can mask these credentials in every showing process to protect their identity from being revealed through a collusion between the CA and the verifiers. The proposed system maintains unlinkability between the issuing and showing protocols. Furthermore, it achieves unlinkability in the showing protocol such that the verifier cannot distinguish a user in two different sessions of the showing protocol. The proposed system is novel and practical in terms of introducing a new multi-show credential system that supports selective disclosure (Some credentials can be disclosed and others kept secret during the showing protocol.) The proposed system is the first that utilizes multilinear maps in the identification protocol. Making use of bilinear pairings and multilinear maps are suitable for IoT devices that have limited capabilities in terms of power consumption, key storage, and computing power. The security analysis of the proposed system is discussed using Burrows–Abadi–Needham (BAN) logic.