In recent years, the development of the Intelligent Transportation System (ITS) has increased the popularity of vehicular ad hoc networks (VANET). A VANET is designed to enable vehicles to exchange information a bout traffic or vehicle conditions to help other vehicles avoid traffic accidents or traffic jams. To resist malicious attacks, all vehicles must be anonymous and their routings must be untraceable, but still verifiable.
The vehicles must trust each other and communicate confidentially. In a VANET, Road Side Units (RSU) are installed on traffic signs or streetlights to help vehicles maintain anonymity, to authenticate messages, or to support confidentiality. However, the coverage of an RSU is limited and the cost of widespread installation is high. RSU installations are incremental, so messages must be authenticated using dense RSUs or sparse RS Us.
In this paper, the concept of random key pre-distribution that is used in Wireless Sensor Networks (WSN) is modified to random secret pre-distribution (RSP), which integrates identity-based cryptography (IBC) to produce a message authentication scheme for VANETs in a sparse RSU environment. In the proposed scheme, vehicles follow a process to determine a common secret, allowing them to authenticate each other and obtain the pairing value as a key for use in message authentication and private communication. Evaluation results show that the proposed scheme outperforms related schemes.
RELATED WORKS AND TECHNIQUES
According to Hubaux et al, a smart vehicle can record, compute, and specify its position. It uses the traditional public-key infrastructure (PKI). The complexity of computation is increased if the vehicle uses PKI to encrypt the messages. The computation overhead of the communication step is also then increased. Moreover, for privacy and un-traceability, the vehicle must frequently change its certificate, imposing a burden on the TA.
PROPOSED SCHEME: RSP-BASED MESSAGE AUTHENTICATION FOR VANET
In the proposed scheme, one day is split into n time slots (T1 ܶ~ Tn) , and the TA maintains a large secret pool that will be pre-distributed randomly to all RSUs and vehicles as information about the original registration set (ORG) at ܶT0. With a pseudo random generator and the same seed value that is provided by the TA in ܶT1 ܶ~ Tn, all RSUs have the same secret pool fr om which to issue the random secret in response to registration requests from vehicles.
ANALYSIS OF SECURITY AND PERFORMANCE
A VANET is vulnerable to various malicious attacks, including masquerading attacks, forgery attacks and reply attacks. To ensure the privacy of vehicles, the proposed scheme must support anonymity, confidential communication, and conditional un-traceability. When a legal vehicle makes a malicious attack, it will be traced and revoked.
CONCLUSIONS AND FUTURE WORK
This paper proposed the concept of the RSP for constructing a message authentication scheme for use in VANETs. In the proposed scheme, all RSUs and vehicles must register with the TA to receive the original registration set (ORG). At any time, all RSUs have a common secret pool that is generated by a PRNG with a common seed value that is sent by the TA in every time slot. The RSUs act as issuers that can assign a sub-set of secrets to any vehicles that have been authenticated with their ORG or NRG, which were obtained in the previous time slot.
For every T1, or whenever vehicles enter the VANET for the first time, vehicles request the new registration set (NRG) with the information in ORG. In other time slots, the vehicles can obtain the new registration set with the information in NRG to generate a new NRG. In the proposed scheme, vehicles randomly choose one of their IDs in NRG and the set of secret index to announce their presence periodically. Using the ID an d secret index set, neighboring vehicles can compute the mutual pairing value or find vehicles that can help them with message authentication.
In message authentication, a polynomial function is formed by the pairing values and the HMAC key. The HMAC of the message with the key will be attached to the broadcast message. Vehicles that receive a broadcast message use their pairing value to retrieve the HMAC key and to authenticate the message. Some vehicles are asked to rebroadcast the message for vehicles that do not have a common secret with the sender.
The proposed scheme is very simple but satisfies all the requirements of a VANET, such as defense against masquerade, forgery and replay attacks, anonymity, un-traceability, message authentication, confidential communication, and a light revocation list. The only computation that is involved in signing and verification for message authentication is that associated with HMAC, so the proposed scheme outperforms previously proposed schemes.
Source: Shu-Te University
Authors: Alan Dahgwo Yein | Yu-Hsiu Huang | Chih-Hsueh Lin | Wen-Shyong Hsieh | Chung-Nan Lee | Zhong-Ting Luo