With the rapid development of cloud computing, an increasing number of individuals and organizations are sharing data in the public cloud. To protect the privacy of data stored in the cloud, a data owner usually encrypts his data in such a way that certain designated data users can decrypt the data. This raises a serious problem when the encrypted data needs to be shared to more people beyond those initially designated by the data owner. To address this problem, we introduce and formalize an identity-based encryption transformation (IBET) model by seamlessly integrating two well-established encryption mechanisms, namely identity-based encryption (IBE) and identity-based broadcast encryption (IBBE). In IBET, data users are identified and authorized for data access based on their recognizable identities, which avoids complicated certificate management in usual secure distributed systems. More importantly, IBET provides a transformation mechanism that converts an IBE ciphertext into an IBBE ciphertext so that a new group of users not specified during the IBE encryption can access the underlying data. We design a concrete IBET scheme based on bilinear groups and prove its security against powerful attacks. Thorough theoretical and experimental analyses demonstrate the high efficiency and practicability of the proposed scheme.

With the establishment of the intelligent transportation system (ITS), the vehicular ad hoc networks (VANETs) play a significant role for improving traffic safety and efficiency. In order to avoid malicious attack and resource abuse in VANETs, the use of digital signature scheme is widely regarded as the first line of defense to achieve a secure VANETs system. However, it is still a challenging task to design a conditional privacy preserving authentication scheme, to resolve security and privacy-preserving problems in VANETs and to improve the utilization ratio of information resources. In addition, the relevant researches show that the tamper-proof device (TPD) is vulnerable to side channel attacks. If the sensitive parameters stored in TPD are extracted, the system would be totally broken. To address these issues, this paper introduces a conditional privacy-preserving authentication scheme with double-insurance supporting batch verification (CPPA-D) for VANETs, which is constructed in cyclic groups on elliptic curves. Either the master private key or the vehicle private key is leaked, it is impossible to forge a valid authenticated message to deceive the recipients, which achieves double-insurance for private keys. When multiple messages are received, our CPPA-D scheme allows the receiver to perform batch verification to improve the efficiency. Security analysis shows that our CPPA-D scheme not only can resist traditional attacks but also can solve the security problems caused by private key stolen in the TPD under side channel attack. There is also a certain advantage in computation overhead according to efficiency analysis and comparison.

Smart grid can greatly improve the efficiency, reliability and sustainability of the traditional grids. In industrial smart grid, real-time user-side metering data may be frequently collected for monitoring and controlling electricity consumption. However, the procedure of frequently metering data collection may lead to sensitive information leakage. To address the security issues in industrial smart grid, we propose an efficient identity-based metering data aggregation scheme supporting batch verification by collector and ESP, respectively, which guarantees the privacy and integrity of metering data. In our scheme, collectors are allowed to collect and aggregate the metering data of users in their respective administrative domain without compromising the confidentiality of metering data. Security analysis demonstrates that our proposed scheme is provably secure in the random oracle and satisfies the above security requirements. Performance analysis indicates that our scheme outperforms existing solutions in terms of communication and computation costs.

Due to the rapid development of demand response management and distributed energy resources, prosumers are becoming more proactive, which also promotes the emergence of peer-to-peer (P2P) energy trading mechanisms. However, we find that it is quite difficult to simultaneously achieve high computational efficiency, decentralized operations and solution optimality in a P2P energy trading mechanism, which is called the “P2P energy trading trilemma”. In this paper, we first propose a novel negotiation mechanism for P2P energy trading that can maximize social welfare in a decentralized manner and respect physical network constraints. Then, the local optimization problem is transformed into a closed-form alternating update algorithm (AUA), so that the computational efficiency can be greatly improved. Therefore, our proposed mechanism solves the “P2P energy trading trilemma” to a certain extent. Another challenge is that the locational marginal price (LMP)-based market mechanism cannot satisfy the incentive-compatible property. To encourage prosumers to cooperate in a lack-of-trust environment, a novel incentive-compatible mechanism is proposed for P2P energy trading using consensus mechanism inspired by proof of solution (PoSo) and smart contract (SC). Finally, we simulate the functionality of the mechanism in terms of convergence performance, reliability, scalability, computational efficiency, and SC operations.

Vehicle ad-hoc networks (VANETs) can offer numerous benefits, but also face many privacy and security issues. There exist the certificate management burden and key escrow issue in traditional public key infrastructure (PKI)-based and identity (ID)-based privacy-preserving authentication schemes, respectively. In addition, the security of some existing cryptographic schemes depends on strong assumptions about the ideal tamper-proof devices. To address these issues, a certificateless aggregate signature (CLAS) scheme for VANETs has been proposed, which was claimed provably unforgeable. However, we found that this scheme cannot resist collusion attacks, which means the equivalent validity of the aggregate signature would be broken. Therefore, this article proposes an improved CLAS scheme against collusion attacks for VANETs (CA-CLAS). Security and performance analyses show that the proposed CA-CLAS scheme not only offers privacy and security guarantees for VANETs, but also improves efficiency compared to existing authentication schemes.

A vehicular ad hoc network (VANET) is a special mobile ad hoc network that provides vehicle collaborative security applications using intervehicle communication technology. The method enables vehicles to exchange information (e.g., emergency brake). In VANET, there are many vehicle platoon driving scenes, where vehicles with identical attributes (location, organization, etc.) are organized as a group. However, this organization causes the issue of security threats (message confidentiality, identity privacy, etc.) because of an unsafe wireless communication channel. To protect the security and privacy of group communication, it is necessary to design an effective group key agreement scheme. By negotiating a dynamic session secret key using a fixed roadside unit (RSU), which has stronger computational ability than the on-board unit (OBU) equipped on the vehicle, the designed scheme can help to provide more stable communication performance and speed up the encryption and decryption processes. To effectively implement the anonymous authentication mechanism and authentication efficiency, we use a batch authentication scheme and a shared secret key mechanism among the vehicles, RSUs and trusted authority (TA). We design an efficient group secret key agreement scheme, which satisfies the above communication and security requirements, protects the privacy of vehicles, and traces the real identity of the vehicle at a time when it is necessary. Computational analysis shows that the proposed scheme is secure and more efficient than existing schemes.