  We study the state-dependent (SD) wiretap channel (WTC) with non-causal
channel state information (CSI) at the encoder. This model subsumes all other
instances of CSI availability as special cases, and calls for an efficient
utilization of the state sequence for both reliability and security purposes. A
lower bound on the secrecy-capacity, that improves upon the previously best
known result published by Prabhakaran et al., is derived based on a novel
superposition coding scheme. Our achievability gives rise to the exact
secrecy-capacity characterization of a class of SD-WTCs that decompose into a
product of two WTCs, where one is independent of the state and the other one
depends only on the state. The results are derived under the strict
semantic-security metric that requires negligible information leakage for all
message distributions.
