On secure communication over the Z-Channel

Abstract

The discrete memoryless Z-Channel (DM-ZC) with a confidential cross-message is considered. Three messages are transmitted; encoder 1 transmits one message to be decoded by decoder 1. Encoder 2 transmits two messages, the first of them is to be decoded by decoder 2; the second message is to be decoded by decoder 1 and is required to be kept secret from decoder 2. The secrecy level is measured by the equivocation rate. An outer bound on a class of degraded DM-ZC is derived. An achievable secrecy-rate region of a special case of this class is obtained. Finally, a general inner bound for the secrecy-capacity region of the DM-ZC is proposed.