VEHICULAR AD HOC NETWORKS GAURAV KORDE KAPIL SHARMA

Origins Based on the principles of Mobile ad hoc networks. Continuously self-configuring, infrastructure-less network of mobile devices connected without wires. Why explore this path?

The players Onboard Units (OBUs) Road side Units (RSUs) The resulting network: VANET RVCs and IVCs

Where do the issues come in? Inherits all the advantages and the disadvantages of MANETs. Some of the issues with regards to security and safety are: High speed mobility of the network entity coupled with the extremely large amount of entities. Conditional privacy preservation.

A good example: Google Driverless Car Google’s state of the art project for ushering in a new era of private cars. Cars are equipped with LIDAR and GPS. Sensors monitor every element in the surrounding. What could go wrong?

IEEE Security and the VSC Project Also known as Dedicated Short Range Communications (DSRC) protocols. Emerged recently to enhance to support wireless communications among vehicles for the roadside infrastructure. The IEEE standard addresses the issues of securing WAVE messages against eavesdropping, spoofing, and other attacks. The security infrastructure is also responsible for the administrative functions necessary to support core security functions such as certificate revocation.

VSC Project Evaluates the feasibility of supporting vehicle safety related applications through the DSRC standards. Proposes to maintain a list of short-lived anonymous certificates. The certificates are blindly signed by the certificate authority (CA). Uses the certificate revocation list (CRL). Obvious disadvantage: Too long CRL.

Continued… For achieving traceability, a unique electronic identity is assigned to each vehicle by which the identity of the vehicle owner can be inspected by the police and authorities in any dispute. Not a scalable and reliable approach because the ID management authority has to keep all the anonymous certificates for the vehicles in the administrative region. Once a malicious message is detected, the authority has to exhaustively search a very large database to find the identity related to the compromised anonymous certificate.

RSU-aided Certificate Revocation With a public key certificate, various attacks can be prevented. However, a certificate of a user may need to be revoked sometimes. In traditional PKI, the most common scheme is CRL. Alternatives to this are a certificate revocation system (CRS), certificate revocation tree (CRT), the Online Certificate Status Protocol (OCSP) among others. However, all of them need a centralized CA. Problem?

To design a suitable and efficient certificate revocation scheme, the following four observations are made: In this case, it is considered that timely notification of certificate revocation events to centralized CAs is infeasible. Insufficient space in OBU to keep an entire CRL. Assumed that CRL kept at OBUs could be incomplete or inaccurate. The movement of a vehicle can be predicted. The RSU can notify OBUs about revoked certificates in the neighborhood.

RCR mechanism Three types of entities: Certificate authority(CA), RSUs and Vehicles. The CAs manage the RSUs and both of them are assumed to be trustworthy. The CA provides each RSU a secret key, while the corresponding public key is an identity string containing the name of the RSU, the physical location, and the authorized message type.

Conditional Privacy Preservation The source privacy of safety messages is a key security issue. Source privacy preservation is critical for a VANET to be considered for practical implementation and commercialization. In, M. Raya and J.P. Hubaux, “Securing Vehicular Ad Hoc Networks”, the authors proposed a security protocol based on anonymous key pairs. It involved installing a large number of short-lived anonymous credentials (probably 43,800) in a vehicle and randomly selecting one of them to sign each message, to ensure the vehicle’s anonymity requirement could be met. Again, problems?

GSIS Protocol Integrating group signatures(GS) and identity based signatures(IS). Meets the security and conditional anonymity requirements for VANETs. Simplifies certificate and ID traceability management. More significantly, it reduces the size of the CRL and minimize the effort of deploying PKI for RSUs.

References “Security in Vehicular Ad Hoc Networks” by Xiaodong Lin, Rongxing Lu, Chenxi Zhang, Haojin Zhu, Pin-Han Ho and Xuemin (Sherman) Shen, University of Waterloo, IEEE Communications Magazine, April 2008