Brijesh Kumar Chaurasia

Message broadcast in VANETs using group signature

In this paper, we study group signature scheme for privacy preservation of a continually transmitting mobile vehicle. A moving vehicle transmits and receives different types of messages on the road. Such communication is a threat to the privacy of a vehicle as its communication can be used to link its identity to its physical entity. The change of size and nature of the neighborhood of a moving vehicle changes as new vehicles come in its vicinity and old neighbors become distant. This change might warrant a pseudonym update for privacy preservation. Moreover, malicious vehicles may broadcast false messages in the network using the identity of other vehicles. This necessitates authentication of the broadcast in addition unlinkability of broadcast messages. Further, a vehicle should not be able to deny its communication, if warranted by law. Thus, a vehicle should be able to broadcast non repudiable, non replicable messages while remaining anonymous. To achieve these conflicting goals of privacy and non-repudiation, group signature schemes along with pseudonyms have been proposed. Group Signature schemes provide security, anonymity to the broadcast, and traceability as required in a VANET. The present work focuses on existing group signature schemes to verify their effectiveness and overheads. Moreover, a scheme to combine pseudonyms and group signature scheme has been proposed to enhance the effectiveness and efficiency of group signatures in VANETs.

Hiding Sensitive Association Rules without Altering the Support of Sensitive Item(s)

Association rule mining is an important data-mining technique that finds interesting association among a large set of data items. Since it may disclose patterns and various kinds of sensitive knowledge that are difficult to find otherwise, it may pose a threat to the privacy of discovered confidential information. Such information is to be protected against unauthorized access. Many strategies had been proposed to hide the information. Some use distributed databases over several sites, data perturbation, clustering, and data distortion techniques. Hiding sensitive rules problem, and still not sufficiently investigated, is the requirement to balance the confidentiality of the disclosed data with the legitimate needs of the user. The proposed approach uses the data distortion technique where the position of the sensitive items is altered but its support is never changed. The size of the database remains the same. It uses the idea of representative rules to prune the rules first and then hides the sensitive rules. Advantage of this approach is that it hides maximum number of rules however, the existing approaches fail to hide all the desired rules, which are supposed to be hidden in minimum number of passes. The paper also compares of the proposed approach with existing ones.

State of the Art of Data Dissemination in VANETs

(Road Side Units) and vehicles disseminate safety and non safety messages. The aim of VANETs is to enable dissemination of traffic information and road conditions as detected by independently moving vehicles. For VANETs applications, it is important to disseminate data from an information source vehicle to many destination vehicles on the road. Dissemination of data in VANETs is used to improve the quality of driving in terms of time, distance, and safety. In this paper, a solution of ensuring data dissemination in vehicular ad-hoc networks for sparse and dense vehicular network is presented. Architecture for data dissemination is also proposed.

Suitability of MANET Routing Protocols for Vehicular Ad Hoc Networks

In this paper, the suitability of the existing MANET routing protocols for VANETs has been evaluated. Even though a VANET is a subset of MANET, it has unique characteristics and message delivery requirements. VANETs are characterized by a very dynamic topology with partial infrastructure support, patterned mobility, mobile nodes with sufficient resources, intermittent connectivity and varied channel behavior. In addition to these characteristics, the network traffic requirements are also different. Safety messages need reliable, accurate and timely delivery in a few hops neighborhood whereas other types of messages may have other requirements. MANET protocols, in contrast, are designed for resource constrained wireless environment. The message delivery constraints are not stringent and movement of nodes is slow and random. Thus, there is a need to ascertain whether, the basic MANET routing protocols like AODV and DSR can satisfy VANET needs like timely delivery of messages especially when the vehicles move at high speeds. Simulation studies show that AODV and DSR are not able to satisfy the requirements and specific VANET routing protocols are needed.

Pseudonym Based Mechanism for Sustaining Privacy in VANETs

This paper addresses the problem of sustaining the privacy of a vehicle in a vehicular ad hoc network (VANET). In a VANET, vehicles broadcast information as they move on the road. The location of a vehicle can estimated using localization techniques and its identity can be read from its messages. A link can be established between the physical vehicle through localization and its identity is a threat to privacy. This localization is not accurate and a vehicle can hide in the crowd of neighborhood vehicles. Further to avoid getting tracked, vehicles use pseudonyms and update these pseudonyms as they transmit. To avoid depletion of pseudonym pool, pseudonym update must be performed only when required. In this work, a strategy has been formulated for pseudonym update to sustain privacy when a vehicle is being observed by an adversary with different capabilities. Results indicate that updating pseudonyms in accordance to the strategy maximizes the privacy of a vehicle.

Trust Computation in VANETs

In this work, we study the application of Perron-Frobenius theorem for computing trust in the VANET environment. Safety critical and safety related messages in a VANET can lead to major changes in the behavior of vehicles moving on the road which can prevent unpleasant traffic situations. False messages can result in serious conditions like collisions. Trust management in VANETs is necessary to deter broadcast of selfish or malicious messages and also enable other vehicles to filter out such messages. A decentralized dynamic trust management system must be scalable with an ability to cope with sparsity of direct interactions. In this work, it is shown that messaging behavior of vehicles can be modeled as a primitive graph. This allows the application of Perron-Frobenius theorem. It is found that the eigenvalues of the matrix corresponding to the interaction graph can be used to compute trust values in the VANET setting.

Conditional privacy through ring signature in vehicular ad-hoc networks

Ring signature allows a signer to disclose reliable information by enabling source authentication while allowing him to be indistinguishable among the possible signers. The scheme is setup free and a vehicle can create a signer group on the fly without taking the consent of the other possible signers to disseminate messages. However, absolute anonymity can be misused. In this paper, a non repudiation mechanism has been proposed in ring signature scheme to make a vehicles privacy conditional. A vehicle can obtain the public keys of the vehicles around it to create a signature. This signature can be used to prove the accuracy of a message without revealing the signers identity. The signer remains hidden in the crowd of his neighboring vehicles and their public keys giving it both location and identity privacy. Simulation results the time taken by the scheme to create signed message and transfer it over the shared wireless channel is in the order of milliseconds for different traffic conditions on the road. This proves the efficacy of the scheme and makes it attractive for VANETs.

Optimizing Pseudonym Updation for Anonymity in VANETS

A vehicle can be tracked through its locatable transmission. The broadcast by a source contains its current identity and also allows estimation of its location by a receiver. This possibility of mapping between the physical entity and the estimated location through the communication broadcast is a threat to privacy. The changes in the location due to motion and the alteration in the temporal identifiers diminish the correlation between location and physical entity. However, such a mapping can still be recognized when an actively communicating node in relative isolation is observed for a sufficient interval of time. This paper addresses the challenges in providing anonymity to a moving vehicle that continually switches identifiers. As a vehicle moves on a road, its neighbors change in accordance to its relative speed with neighboring vehicles. This change in the nature and size of the neighborhood, i.e. the entropy, the degree of the anonymity of a vehicle. It is shown that the effective entropy reduces drastically due to change in the neighbors and transmissions by vehicles. The work studies the possibility that a node may retain its anonymity by switching identities in the vicinity of other vehicles to decorrelate its location and identity relation. A heuristic that allows a vehicle to switch its identity at a time and place where the potential of anonymity preservation can be maximized by increasing the entropy is proposed. The performance of the proposed heuristic is evaluated in a highway environment with vehicle mobility and dynamic vehicle population. Simulation results indicate that updating pseudonyms in accordance to the heuristic maximizes the entropy and through it, the anonymity of a vehicle.

Mechanism for Privacy Preservation in VANETS

This paper proposes a mechanism for sustaining privacy of a vehicle in a vehicular ad hoc network VANET through pseudonym update. In a VANET, vehicles on the road are involved in dissemination of information as they move. An association can be formed between the physical location of the source vehicle and the transmitted messages. This relationship between the physical vehicle and its identity can breach its privacy. In this work, a strategy for optimal pseudonym update for maximizing privacy has been formulated when a vehicle is being observed by adversaries with different capabilities. Results indicate that updating pseudonyms in accordance to the strategy maximizes the privacy of a vehicle in the given situation.

Haste induced behavior and VANET communication

In this paper, the impact of the knowledge of non local traffic state through vehicular ad hoc network (VANET) communication on traffic stability is studied through microscopic traffic simulation. In particular, the effect of this communication through modification of driver behavior is evaluated. Intra-driver behavior such as non negligible reaction time, anticipation, limited attention spans and perception error affect his inter-driver behavior like lane changing, keeping safe gap etc. Intuitively, it is felt that this behavior is further conditioned by external factors like frustration due to falling behind predefined schedules, congestion, inability to overtake or change lanes and behavior of other drivers etc. The warning and safety messages from other vehicles increase the available maneuvering time and mitigate the effects of intra-driver behavior. The look ahead capability allows the driver to plan his journey and eschew risks like shortened safety gap, lane changing frequency etc. Simulation results for various traffic scenarios demonstrate the potential of VANET communications on safety and traffic stability through modification of driver behavior.