Car accidents kill or injure millions of people every year. Vehicular communication (VC) systems and Cooperative Intelligent Transportation Systems (C-ITS) were introduced to increase road safety and reduce the number of accidents through...
moreCar accidents kill or injure millions of people every year. Vehicular communication (VC) systems and Cooperative Intelligent Transportation Systems (C-ITS) were introduced to increase road safety and reduce the number of accidents through the use of information and communication technologies.
A self-organized network called a Vehicular Ad-hoc Network (VANET) can be formed in which each vehicle, equipped with wireless communication devices, can broadcast high update rate periodic safety messages (beacon messages) to let other vehicles know about environmental conditions and their neighboring vehicles.
The capability of this technology in very low-latency (latency critical) broadcast communications to use in hazardous situations has emerged as a promising approach toward increasing road safety and efficiency, as well as improving driving experience. Latency defines an allowable time frame between when information is generated for transmission and when it is received.
The C-ITS and VANET applications are vulnerable to potential cyber attacks involving message manipulation. The beacons contain vehicle status, such as speed and location details. Attackers can disrupt services by changing, forging or intercepting this information.
A solution for this problem is cryptographic authentication. A unique identifier is provided to a vehicle for authentication purposes. However, this vehicle identifier can be associated with an identifiable individual. In this case, the data becomes personal information. In addition, an adversary can capture communications and link the identifiers to specific vehicles, and consequently to the drivers (ID disclosure), providing a means for surveillance.
To avoid this, for both identification and message authentication, protection of the driver's identity during authentication must be guaranteed. A mechanism is required to provide message anonymity to other entities, but enables identification by a trusted party.
A privacy preserving authentication strategy must be used such that the privacy of a user is maintained during authentication period. Nevertheless, the mechanism should only offer automatic anonymity while the vehicle actually follows the security rules and regulations. In the event of a malicious action, the vehicle identifier has to be well tracked.
The beacon content confidentiality is another concern. The vehicle size attribute, acceleration, speed, steering angle, and position within a beacon message helps an observer to decide which beacon to link to a single vehicle.
From a practical perspective, different cars may have different processing capacities to support C-ITS applications such as vehicular safety. For economic reasons, car manufacturers embed small-scale and low-cost hardware for vehicular communications. This constrains the mechanisms applicable to secure modern vehicles against cyber attacks. The limited in-car computational capabilities make complex cryptographic techniques economically unattractive.
To secure VANET communications against cyber threats, security standards such as IEEE 1609.2 and ETSI TS 103 097 are proposed. These standards describe security services for applications and specify the use of specific cryptographic algorithms for message exchanges in the vehicular environment. However, it is not clear how and to what extent the inclusion of IEEE 1609.2 recommended authentication algorithms affects verification time of the messages. In addition, other standards bodies have begun standardizing various pairing-based schemes. The IEEE 1609.2 security standard has not yet selected any pairing-based scheme, leaving the settings related to pairing-based cryptography in the vehicular environments unspecified.
Many security and privacy challenges are not addressed in the current security standards, such as IEEE 1609.2 and ETSI TS 103 097. Research aimed at tackling this problem has resulted in the proposal of multiple authentication protocols. However, to date there is no generic framework and model to support the comparison of these protocols and provide guidance for design and evaluation.
Any cryptographic technique for authentication requires the use of a cryptographic key. Thus, a key-management mechanism is necessary to protect keying material against threats. A cryptographic system requires key-management techniques to control the distribution, use, update, and revocation of cryptographic keys.
Unfortunately, existing proposals for privacy-preservation authentication are not effective and efficient in VANETs, since most of them do not take the scalability, computation, and communication overhead into consideration, or they fail to satisfy the security and privacy requirements. Moreover, in many existing studies, a proper key-management strategy to allow parties to establish and update cryptographic keys for security-sensitive operations is a missing component.
The major objective of this research is to develop a secure, efficient, and conditional privacy-preserving authentication and key-management scheme for latency-critical applications in C-ITS. Besides, the work presented in this thesis makes several related contributions.
The first contribution of this thesis is the development and evaluation of a taxonomy and framework to provide comprehensive guidance on the design, evaluation, and analysis of both existing authentication protocols in the public literature and future proposals. This enables designers and investigators to adequately compare and select authentication schemes when deciding on specific protocols to implement in a particular application. The framework can be applied in design, making choices appropriate for the intended context. This framework is also applied in the design and development of the new protocol presented in this thesis.
The second contribution of this thesis is the development of a model to categorise authentication protocols in suitable categories, including: safety-critical and non-safety-critical, and analyse the delay produced by an authentication protocol. This predicts impacts of the delay on a possible crash in the real-world scenarios. This model is applied in the evaluations presented in this thesis.
The third contribution of this thesis is the implementation and evaluation of the efficiency of the cryptographic primitives recommended in the IEEE 1609.2 security standard to authenticate the low-latency safety messages. This research shows how and to what extent the authentication overhead of latency-critical messages may impact on driver safety. The research findings should help the IEEE 1609.2 security standard to select appropriate parameters for future use in VANETs. The results also help to improve efficiency and reduce authentication delay of the scheme proposed in this thesis.
The fourth contribution of this thesis is the implementation and evaluation of the cryptographic primitives for pairings (a variant of elliptic curve cryptography). This work investigates the effect of pairing-based cryptography on authentication in vehicular networks, and shows how and to what extent the authentication overhead of latency-critical messages may impact on driver safety. The research findings may help the IEEE 1609.2 security standard to select appropriate pairing-curve combinations for future use in VANETs. The results also help to select appropriate cryptographic primitives in design of the scheme proposed in this thesis.
The fifth contribution of this thesis is the identification of a flaw and suggested modification to mitigate this flaw in the system-key update protocol of a well-known authentication scheme named 2FLIP: A Two-Factor Lightweight Privacy Preserving Authentication Scheme for VANET. This research demonstrates that the proposed scheme could not achieve the claimed security goals. However, the scheme is efficient, so this research proposes a modification to enhance the security of the 2FLIP system-key update protocol while maintaining the efficiency. This is supported by formal security proof to demonstrate that the modified protocol is indeed provably secure.
The sixth contribution of this thesis is the development and evaluation of a new secure, efficient, and privacy-preserving scheme; proposing Anonymous Lightweight Inter-vehicle (ALI) broadcast authentication with encryption. This research combines a message authentication scheme with beacon encryption to provide a higher level of anonymity. The formal security proof and extensive performance evaluation demonstrate efficiency, effectiveness, and applicability of the proposal.
