Security of quantum protocols against coherent measurements

The goal of quantum cryptography is to design cryptographic protocols whose security depends on quantum physics and little else. A serious obstacle to security proofs is the cheaters ability to make coherent measurements on the joint properties of large composite states. With the exception of commit protocols, no cryptographic primitives have been proved secure when coherent measurements are allowed. In this paper we develop some mathematical techniques for analyzing probabilistic events in Hilbert spaces, and prove the security of a canonical quantum oblivious transfer protocol against coherent measurements. 1 Introduction Work on quantum cryptography was started by Wiesner Wi70 twenty-five years ago. Much knowledge on how to exploit quantum physics for cryptographic purposes has been gained through the work of Bennet and Brassard (BBBW83BB84BBBSS92), and later Crepeau (Cr90BC91BBCS92Cr94). Furthermore, prototypes for implementing some of these This research was...