Vehicular Adhoc Networks (VANETs) promises to empower the future autonomous vehicles with a cooperative awareness facility that will help in avoiding accidents and alleviating traffic congestion. The foreseen collective awareness requires the vehicles to communicate with their neighbors and with the infrastructure; such communication will need the fulfillment of many requirements such as security, privacy, and efficiency. The Dedicated Short-Range Communication (DSRC) standard has been formulated to afford these requisites. On one hand, when focusing on the application layer, DSRC adopts the successful Internet-based Public Key Infrastructure (PKI) framework to safeguard the vehicles. However, PKI alone cannot comprehensively meet all of the security and privacy requirements. On the other hand, the DSRC 's Medium Access Control (MAC) layer adopts the IEEE 802.11p access mode, which also needs augmentation to fulfill the efficiency of communication when collisions arise for safety beacons. Since many issues have not been well addressed in DSRC, academic, industrial, and governmental research has flourished over the last two decades to complement the standard. As being part of such large research community, we also have been incentivized to contribute with our own solutions. Our contributions have been ranging between two limits: either finding solutions to acclimate with the available DSRC shortcomings or disregarding the bias that DSRC has towards using only specific standards by bringing other alternative frameworks into scene. With the first direction in mind, our efforts are a mixture of high-level re-arrangement protocols such as grouping and overhead omissions to minimize the PKI and Carrier Sense Multiple Access - Collision Avoidance (CSMA/CA) privacy and efficiency shortcomings. For the other direction, we especially address the application layer level. Since some frameworks have small communication overhead while others have high anonymous traits, we have attempted low-level alternatives to PKI and Elliptic Curve Integrated Encryption Scheme (ECIES) and to overcome their confidentiality, privacy, and efficiency limitations. First, to augment the security of sensitive non-safety applications in PKI, our first research track concerns itself with finding alternatives for the used low-level encryption primitive such as ECIES and Advanced Encryption Standard (AES). The reason behind such effort is the authentication-dependability of ECIES/AES and key management of AES; therefore, we investigate the suitability of using a state-of-the-art low-level partial homomorphic encryption scheme to generate encrypted identities and keys to secure the sensitive non-safety data transfer. Our second research track concerns itself with preserving location privacy of vehicles since PKI does not afford privacy. To avoid the available privacy preservation solutions' covering-encryption overhead and silent-periods' lack of communication, we propose the idea of making vehicles create dynamic mix zones using an alternative super anonymous authentication scheme to hide their pseudonym change. Our third contribution falls within the augmentation of efficiency of communication when safety beacons collisions arise due to limited medium, CSMA/CA access mode, and PKI beaconed overhead. In this regard, we use the concept of grouping and overhead reduction to lower the vehicles' competition for the channel. Rather than having many individual vehicles communicate their information to the infrastructure, group leaders become main figures of communication. Our fourth work focuses on building an efficient identity based alternative authentication for VANETs other than PKI with the goal of having less communication overhead. Our built framework has fast computations, no elliptic curves pairings, smaller communication overhead, and more anonymous usage of pseudo identities to achieve the needed privacy. Focusing on the efficiency aspect of vehicular communication, in the fifth exerted effort, rather than using only PKI to authenticate users, we introduce a context aware authentication interchange protocol to match the situational neighborhood conditions of vehicles. If it is a dense network, our scheme switches to use a lower overhead authentication scheme; if it is a sparse network, the vehicle automatically switches to a more anonymous authentication.
In a nutshell, the domain of VANETs offers a unique set of challenges; yet they present immense opportunities for research. We address three major challenges and suggested five research directions that may help in overcoming these limitations. We hope through these tracks of research to cast a light on the suitability of new concepts in affording the security, privacy, and availability of VANETs communications while achieving a comparable performance to the already adopted schemes.