Resisting relay attacks on vehicular Passive Keyless Entry and start systems

Passive Keyless Entry and Start (PKES) systems are popularly embed in modern cars, which allow users to open and start their cars while having their car keys´ in their pockets. They bring convenience to users but are vulnerable to relay attacks. A relay attack to PKES is a widely known attack against the challenge- response technique used in the passive keyless vehicle system, which allows to open and start the car while the true distance between the key and car remained large. The main countermeasure against relay attacks is the use of distance bounding protocols measuring the round-trip time between the car and the key. However, most schemes tend to a more complex design to decrease adversary´s success probability. In this paper, we propose a novel distance bounding protocol to resist relay attacks in PKES systems, using only 2n bits of memory, which, to our best knowledge, is equal to Hancke and Kuhn´s protocol and less than any existing protocols. In addition, by using our protocol, the key is able to detect adversary´s malicious queries. We also make a comparison with typical previous distance bounding protocols in both memory and mafia fraud success probability.