Abstract. It is often the case in applications of cryptographic protocols that one party would like to determine a practical upper-bound on the physical distance to the other party. For instance, when a person conducts a cryptographic identi cation protocol at an entrance to a building, the access control computer in the building would like to be ensured that the person giving the responses is no more than a few meters away. The \distance bounding" technique we introduce solves this problem by timing the delay between sending out a challenge bit and receiving back the corresponding response bit. It can be integrated into common identi cation protocols. The technique can also be applied in the three-party setting of \wallets with observers" in such a way that the intermediary party can prevent the other two from exchanging information, or even developing common coin ips.
Distance bounding protocols REF , utilize characteristics of the communication medium to put an upper bound on the distance between two nodes.
Distance-Bounding Protocols (Extended Abstract)
EUROCRYPT’93, Lecture Notes in Computer Science 765
Computer Science