In recent years, many researchers have applied aggregated signature techniques to resource-constrained vehicular Ad Hoc networks (VANET) authentication scenarios. We reviewed two recent VANET authentication schemes based on certificateless aggregated signatures (CLAS) while demonstrating that neither of them is resistant to public key replacement attacks under their security models. An eavesdropper can successfully forge a legitimate signature to perform malicious operation. To further address the above security flaws, we propose an improved CLAS scheme for VANET. Considering that some researchers have briefly or even incorrectly used forking lemmas in their security proofs to prove an insecure CLAS scheme, we further improve and refine the security model and security proof method for CLAS, which make the proof process transparent by using general forking lemma. Based on these improvements, our scheme can resist attacks from two types of adversaries in the CLAS security model. In the final performance analysis, the improved CLAS scheme outperforms the secure related scheme of recent years in terms of both computational and communication efficiency. Therefore, our proposal is more suitable for resource-constrained VANET environments.

Nowadays, as an essential technique for intelligent transportation, vehicular ad hoc networks (VANETs) has significantly improved people’s travel experience, providing richer, and smarter services for vehicles while ensuring driver safety. However, considering that VANETs are complex, some security challenges still remain, including but not restricted to privacy preserving of vehicles, authentication of messages, limited resources in computational power, and network bandwidth. To address these issues, many privacy-preserving identity authentication schemes for VANETs have been proposed recently. However, these schemes still suffer some limitations. First, their computational overheads are heavy due to the complex calculations. Second, some schemes are vulnerable to various security weaknesses, unable to resist normal attacks. Third, in some schemes, the same pseudonym keeps unchanged and it is linked to the corresponding private key of user. The consequence is that if the user wants to change its pseudonym, the corresponding private key must be changed. In order to further solve the above problems, we propose a novel privacy-preserving identity authentication protocol based on the certificateless aggregate signature scheme, allowing the user to generate a fuzzy identity to hide her real identity, and the private key can be kept unchanged even if the corresponding pseudonym is updated. Furthermore, to achieve efficiency in computation, bilinear mapping is avoided in our proposed scheme. We prove that our protocol satisfies unforgeability in the random oracle based on a classic complexity assumption. Finally, the security and efficiency analyses demonstrate that our construction enjoys more security features and better performance compared with the existing schemes.

In recent years, the development of Internet of Things technology has led to a surge in interest in the Vehicular Ad-Hoc network (VANET), which has greatly improved travel efficiency and facilitated vehicle data sharing. To ensure the privacy and security of both vehicles and personnel, researchers have proposed various measures for securing VANET systems. Recently, certificate-based aggregate signature (CBAS) schemes have been proposed to design an identity authentication protocol for the VANET to prevent tampering and corruption of private vehicle data. In this study, we conduct a security analysis of the previous CBAS scheme by presenting a security attack. Afterward, we propose a novel and concrete construction of the CBAS scheme that offers improved performance for VANET, which can enhance protection in the VANET scenario. We also demonstrate its security based on standard cryptographic assumptions. Comparative results from theoretical analysis and experimental evaluation illustrate the practicality of our proposed scheme. Similarly, the identity authentication protocol created based on the above CBAS scheme has the properties of dynamic anonymity, mutual identity authentication, unforgeability.

In the vehicular ad-hoc network (VANET), the communication between the vehicle and other nodes is performed in an open channel, which puts forward the requirements for its privacy security and message integrity. Most previous protocols either frequently verify identities before accepting traffic information or do not involve identity revocation mechanisms, and they may assume that third parties are fully trusted. To further solve the above problem, a certificateless-based anonymous and revocable authentication protocol for vehicle-to-vehicle communications is proposed in this paper. Our construction separates the identity authentication process from the traffic message verification, which not only avoids the disadvantage of frequent identity revocation list (IRL) checking but also reduces the overhead in communication and message authentication. These features can make “identity authentication once, broadcast efficiency" really happen. In addition, since our authentication process is based on certificateless signature, it can resist malicious key generation centers (KGC) and road-side units (RSU), which is very necessary for privacy-sensitive application scenarios. Finally, the performance analyses show that our proposal is superior to the existing schemes in terms of authentication speed and communication overhead.

To achieve security of mobile payments within insecure public communication networks, in 2018, a secure transaction scheme for mobile payments is constructed by Yeh from a certificateless signature (CLS) scheme without bilinear pairing Yeh, (2008). However, we point out that this CLS scheme is insecure, and a malicious users can create a valid forged signature on any new message by performing public key replacement attacks. The security flaws of the underlying CLS scheme cause that the upper transaction scheme cannot keep its claimed security. In this article, we describe how this forgery attack works against the CLS scheme, which demonstrates that Yeh’s scheme cannot achieve its original security. Furthermore, to further solve the above-mentioned security flaws, a concrete construction of CLS scheme with improved security is presented. Our improved scheme can be rigorously proved using Forking lemma in the random oracle model, assuming that solving the discrete logarithm problem is infeasible. Finally, a secure transaction scheme for android-based mobile payments is proposed from our improved CLS scheme.

Glyptostrobus pensilis, belonging to the monotypic genus Glyptostrobus (Family: Cupressaceae), is an ancient conifer that is naturally distributed in low-lying wet areas. Here, we report the complete chloroplast (cp) genome sequence (132,239 bp) of G. pensilis. The G. pensilis cp genome is similar in gene content, organization and genome structure to the sequenced cp genomes from other cupressophytes, especially with respect to the loss of the inverted repeat region A (IRA). Through phylogenetic analysis, we demonstrated that the genus Glyptostrobus is closely related to the genus Cryptomeria, supporting previous findings based on physiological characteristics. Since IRs play an important role in stabilize cp genome and conifer cp genomes lost different IR regions after splitting in two clades (cupressophytes and Pinaceae), we performed cp genome rearrangement analysis and found more extensive cp genome rearrangements among the species of cupressophytes relative to Pinaceae. Additional repeat analysis indicated that cupressophytes cp genomes contained less potential functional repeats, especially in Cupressaceae, compared with Pinaceae. These results suggested that dynamics of cp genome rearrangement in conifers differed since the two clades, Pinaceae and cupressophytes, lost IR copies independently and developed different repeats to complement the residual IRs. In addition, we identified 170 perfect simple sequence repeats that will be useful in future research focusing on the evolution of genetic diversity and conservation of genetic variation for this endangered species in the wild.