Lin recently claimed that the privacy-preserving aggregation authentication scheme (PPAAS) based on a certificateless aggregation signcryption scheme (CASS) proposed in our paper (IEEE Transactions on Information Forensics and Security, vol.17, pp.317-331, Jan.2022) suffers from a forgery attack from type II adversary. In this paper, we show that this attack is not valid since the adversary outputs a trivial forged ciphertext. Specifically, the adversary has the master secret key and randomly selects the secret values of all users.

As cities become smarter, the importance of vehicular ad hoc networks (VANETs) will be increasingly pronounced. To support latency- and time-sensitive applications, there have been attempts to utilize fog-cloud computing in VANETs. There are, however, a number of limitations in existing fog-cloud based VANET deployments, ranging from computation and communication bottlenecks to privacy leakage to costly certificate/ pseudonym management to key escrow, and so on. Therefore, in this paper we propose a privacy-preserving aggregation authentication scheme (PPAAS). The scheme is designed for deployment in a safety warning system for fog-cloud based VANETs. Specifically, the PPAAS scheme is realized using a novel efficient anonymous certificateless aggregation signcryption scheme (CASS) proposed in this paper, and allows a fog node to aggregate signcrypted traffic-related messages from surrounding vehicles into an aggregated ciphertext and unsigncrypt them in a batch. We then evaluate the security of PPAAS and demonstrate that it supports confidentiality, authentication, and (efficient) conditional privacy, and key escrow freeness. In particular, our scheme is the first in the literature to achieve efficient conditional privacy, which avoids the need for costly pseudonym management. We also demonstrate that the scheme is practical, based on our simulation results.

With the development of vehicular ad hoc network (VANET) technology, more and more smart parking systems in VANETs are presented. However, existing solutions suffer from the challenges of dishonest parking lots that may claim there are more empty spots than they actually have, malicious occupation of parking spots and multi-reservation attack, etc. To address these challenges, we propose a secure and reliable smart parking protocol based on blockchain and linkable group signatures. For the security of our scheme, it not only realizes traditional authentication, privacy preservation and message confidentiality requirements but also prevents multi-reservation attack and the dishonest parking lots that claim more empty spots than they actually have.