With the growing demand for instant messaging, securing group chats has become a critical concern. While cryptographic approaches are essential for this purpose, they typically require secure and efficient protocols for either group key agreement or group key distribution. Most existing solutions struggle to achieve efficient key updates and seamless integration with real-world systems. To address these limitations, we We present ChatKID, an identity-based group key distribution protocol. At the architectural level, ChatKID employs an asymmetric design to address the resource imbalance between the group owner and group members in group key distribution. At the technical level, it develops a novel polynomial-based key derivation method that drastically improves key update efficiency, while its compliance with the SM9 cryptographic standard enables easy integration with numerous systems. We provide formal analyses of correctness and security, including resilience against five common attacks (e.g., man-in-the-middle, replay), and achieve forward and backward secrecy. Subsequently, we compare ChatKID with recent protocols and demonstrate its significant advantages in both storage and communication overhead. Notably, for group members—typically resource-constrained mobile devices—ChatKID reduces overhead by one to two orders of magnitude (i.e., to$1/10\sim 1/100$) compared to others. Furthermore, we compare ChatKID with mainstream instant messaging applications and demonstrate advantages in terms of connection dependency, computational overhead, communication overhead, and storage requirements. Finally, simulation experiments indicate its superior performance in typical instant messaging scenarios. Taken together, these results suggest that ChatKID holds significant promise for advancing group key distribution in real-world instant messaging applications.

Smart vehicle applications play a crucial role in intelligent transportation systems, enabling sensor-equipped vehicles to establish dynamic networks for efficient collection, sharing, and aggregation. This significantly enhances road security and efficiency by transmitting crucial information to traffic authorities. However, partial research on certificateless aggregation signcryption (CLAS) scheme reveals an intriguing phenomenon where each proposed scheme consistently exhibits numerous security vulnerabilities, particularly susceptible to public key replacement attacks. To address these challenges, this paper proposes a blockchain-assisted certificateless aggregation sign-cryption scheme (BACLAS), leveraging blockchain technology to securely store users’ public key on a distributed ledger and prevent public key replacement attacks effectively. Furthermore, it is a provably secure communication scheme for real-world Vehicle-to-Infrastructure (V2I) communication while addressing practical security concerns. The BACLAS scheme ensures security in terms of existential unforgeability against adaptive chosen message attacks (EUF-CMA) and indistinguishability against adaptive chosen ciphertext attacks (IND-CCA2) based on the hardness assumption of the elliptic curve discrete logarithm problem and computational Diffie-Hellman problem in the random oracle model. The proposed scheme effectively reduces computational costs and time consumption, resulting in a significant reduction of the computation burden ranging from 50.02% to 88.28% compared to other competitive schemes. Moreover, it successfully addresses the key-escrow problem, thereby achieving enhanced security properties.

Mobile crowdsourcing is the practice of hiring a number of people (workers) at a low cost to complete tasks that are typically difficult to complete individually. However, in the IoT era, how to achieve lightweight privacy preservation and evaluate the trust of human mobility are crucial matters. Therefore, this article proposes a blockchain assisted Privacy-Preserving mobile crowdsourcing scheme based on threshold blind signatures (TBSCrowd for short). We design a blockchain assisted Privacy-Preserving mobile crowdsourcing scheme which can preserve security, robustness, fairness while reducing computation and communication overheads of scheme. To achieve the properties of privacy, unforgeability and robustness, we propose robust asynchronous ECC threshold signatures. Simulations are conducted to show the performance of the TBSCrowd scheme, and the experiment results demonstrate that our construction significantly outperforms some related schemes in security and other related aspects.

With the rapid advancement of wireless communication and autonomous driving technology, vehicular ad hoc networks (VANETs) has emerged as a robust network facilitating interactive communication among vehicles, roadside infrastructure, and the surrounding environment. However, VANETs face challenges regarding traffic information security and vehicle identity privacy during wireless transmission. Vehicles require reliable technology to communicate efficiently and securely with roadside infrastructure, especially at high speeds. To address these issues in VANETs environments characterized by diverse nature of vehicles and roadside units (RSUs), we propose an enhanced certificateless and identity-based offline/online heterogeneous signcryption (CLIOOHSC) scheme for VANETs, aiming to achieve confidentiality, integrity, authentication and identity anonymity simultaneously in a unified step. The CLIOOHSC scheme enables vehicles in certificateless cryptography (CLC) environment to transmit messages to RSU in identity-based cryptography (IBC) environment. In the online phase, scalar multiplication operations are omitted since they are performed in the offline phase, significantly reducing the computational load. Then, through security proofs, we demonstrate that the proposed scheme can achieve the expected security properties. The performance analysis shows that our scheme is superior to other schemes in terms of computation and communication costs and is suitable for scenarios where vehicles communicate across cryptosystems.

Industrial Internet-of-Things (IIoT for short) which is the basis of Industry 4.0, extends Internet connectivity beyond traditional computing devices, for example, smartphones, computers, laptops, webcams, etc., to the physical world for improving accuracy and efficiency while reducing the production cost. However, there exists large numbers of security threats, such as data leakage and privacy threats. To solve these issues, we first present a system model, security requirements and then proposed a post quantum secure multi-party collaborative signature with deterability in the IIoT environment. In this scheme, formal security proofs are given in the random oracle assuming that AMLWE and AMSIS problem are hard. We also demonstrate the potential utility of our proposed scheme by evaluating its performance.

Most of the cryptographic protocols currently in use are not appropriate for Internet of Things (IoT) environments because of their huge computing overhead, especially for terminal-embedded devices with resource constrained. Moreover, the computing resources in IoT environments are frequently asymmetric, that is to say, the computing power of the terminal devices is always weak and the server side is relatively stronger. In order to guarantee the security in the scenario, we present the asymmetric computing cryptosystem. Take the key exchange protocol as an example, we show how to construct ACKE, an asymmetric computing key exchange protocol, by employing the Diffie–Hellman key exchange protocol and the Subset Product problem (NP-complete) in this article. The underlying idea this construction is to significantly decrease the computational complexity of one party, and allow for a suitable rise in the computational complexity of another party. Our proposed protocol is implemented on an IoT simulation platform composed of a notebook PC of Intel i5-5200U 2.2 GHz/8G and a smart watch of MTK6062 1.2 GHz/512M. The experimental results show that this work will assist in making the Diffie–Hellman type protocol suitable for practical applications in IoT environments.