Vehicular Ad-hoc Networks (VANETs) enable the connection and information exchange between vehicles and transportation infrastructure (V2I), vehicle and vehicle (V2V) to improve the safety and efficiency of the transportation system. In previous protocols, V2I and V2V authentication protocols based on bilinear pairings or identity-based cryptography are computationally heavy or difficult to protect the user’s identity and privacy. In addition, lightweight authentication protocols have not achieve both V2I and V2V authentication, and may suffer from Onboard Unit (OBU) intrusion attacks, Roadside Unit (RSU) captured attacks, and difficult to track malicious vehicles. Therefore, a lightweight and anonymous V2I and V2V authentication protocol with batch verification based on Elliptic Curves Cryptography (ECC) is proposed. We use Physical Unclonable Function (PUF) and biological key to avoid RSU captured attacks and OBU intrusion attacks, design a feature embedding strategy with dynamic pseudo-identity to recover the malicious vehicle’s identity by the Trusted Authority (TA). In the application test simulating the actual scenario, our protocol is more efficient because of lower overhead and batch authentication strategy. The semantic security of the protocol is formally proved under the random oracle model. The comparative analysis and security proof results show that our protocol is more superior to others.

As one of the most valuable vehicle-based Internet of Things (IoT) applications, Vehicular Ad-hoc Networks (VANETs) have received extensive attention since it was proposed. In order to ensure the safety of VANETs and improve the communication efficiency between moving vehicles and different Roadside Units (RSUs), some handover authentication protocols for VANETs have been proposed. However, the existing protocols have some problems such as excessive computation overhead, untraceable malicious messages, and the inability to resist RSU captured attacks. To solve the above problems, we propose a blockchain-based protocol to achieve Vehicle to Infrastructure (V2I) authentication, V2I handover authentication, and Vehicle to Vehicle (V2V) broadcasting authentication. The advantages of our protocol are: (1) It achieves lightweight V2I handover authentication and V2V broadcast authentication, dynamic anonymity strategy and embedding strategy of pseudo-identity and vehicle feature are used to guarantee anonymity and traceability simultaneously; (2) The announcement can be broadcasted verifiably without the help of transportation infrastructure (e.g., RSU) or the Trusted Authority (TA); and (3) The Physically Unclonable Functions (PUF) technology is used to resist RSU captured attacks. We use formal security proof under random oracle model to prove the security of the proposed protocol. Compared with related V2I handover authentication protocols, our protocol can resist RSU captured attacks and other various known attacks. The sum of first and handover authentication efficiency of our protocol is 37.93% higher than the previous most effective protocol while maintaining the same level of communication and storage costs.

Telecare Medical Information Systems (TMIS) provide an effective way to enhance the medical process between doctors, nurses and patients. For enhancing the security and privacy of TMIS, it is important while challenging to enhance the TMIS so that a patient and a doctor can perform mutual authentication and session key establishment using a third-party medical server while the privacy of the patient can be ensured. In this paper, we propose an anonymous three-party password-authenticated key exchange (3PAKE) protocol for TMIS. The protocol is based on the efficient elliptic curve cryptosystem. For security, we apply the pi calculus based formal verification tool ProVerif to show that our 3PAKE protocol for TMIS can provide anonymity for patient and doctor while at the same time achieves mutual authentication and session key security. The proposed scheme is secure and efficient, and can be used in TMIS.

Single sign-on (SSO) is a new authentication mechanism that enables a legal user with a single credential to be authenticated by multiple service providers in a distributed computer network. Recently, Chang and Lee proposed a new SSO scheme and claimed its security by providing well-organized security arguments. In this paper, however, we demonstrative that their scheme is actually insecure as it fails to meet credential privacy and soundness of authentication. Specifically, we present two impersonation attacks. The first attack allows a malicious service provider, who has successfully communicated with a legal user twice, to recover the user's credential and then to impersonate the user to access resources and services offered by other service providers. In another attack, an outsider without any credential may be able to enjoy network services freely by impersonating any legal user or a nonexistent user. We identify the flaws in their security arguments to explain why attacks are possible against their SSO scheme. Our attacks also apply to another SSO scheme proposed by Hsu and Chuang, which inspired the design of the Chang-Lee scheme. Moreover, by employing an efficient verifiable encryption of RSA signatures proposed by Ateniese, we propose an improvement for repairing the Chang-Lee scheme. We promote the formal study of the soundness of authentication as one open problem.