Key-Message Security over State-Dependent Wiretap Channels

The state-dependent (SD) wiretap channel (WTC) with non-causal channel state information (CSI) available at the encoder is considered. An inner bound on the trade-off region between admissible secret key (SK) and secret message (SM) rates is provided. The result is derived under the stringent semantic-security metric. Our inner bound recovers the best-known achievability results for either SK generation, SM transmission, or simultaneous execution of both. Since some of these past benchmarks were derived under weaker security metrics, our results imply that an upgrade to semantic-security is possible without inflicting any rate loss. It is shown that for certain instances of the considered SD-WTC, the derived region is strictly larger than the previously best-known SK-SM trade-off region reported by Prabhakaran et al., and that a recently reported SK rate for this setup cannot be achieved.