Cryptographic Key Agreement for Mobile Radio

The problem of establishing a mutually held secret cryptographic key using a radio channel is addressed. The performance of a particular key distribution system is evaluated for a practical mobile radio communications system. The performance measure taken is probabilistic, and different from the Shannonmeasure of perfect secrecy. In particular, it is shown that by using a channel decoder, the probability of two users establishing a secret key is close to one, while the probability of an adversary generating the same key is close to zero. The number of possible keys is large enough that exhaustive search is impractical. r 1996Academic Press, Inc.