Rate-distortion theory for the Shannon cipher system

Abstract

Considers Shannon's cipher system with a memoryless broadcast channel. The source output sequence {S/sub l/}/sub t//sup /spl infin//=1 is independent drawings of a random variable S taking values in S, and the key W/sub k/ is a random variable which is independent of S. For simplicity, we assume that the main channel (X/spl rarr/Y) is less noisy than the wiretap channel (X/spl rarr/Z). The security of the system can be measured by the uncertainty or the attainable minimum distortion of the wiretapper who gets only Z/sup N/. For each case, we define the admissible region.<>