receiver and build on the *wiretap* channel model [@csiszarKorner:78]. Our results indicate that the achievable secret-key rate can be significantly higher compared to the results in [@mitrapant:06; @chenVinck:06; @LiuChen:07]. Recently an improved lower bound for the wiretap channel with causal state information at the transmitter and receiver has been reported in [@khiangElGamal:10]. Interestingly it uses a block markov coding scheme, where a secret key is generated in each block as an intermediate step.

After the conference papers [@khisti:09; @khisti:10] on which this paper is based appeared, the authors became aware about a recent work [@prabhakaran:09] where a similar secret-key agreement scheme over channels with noncausal channel state information is presented. This scheme is used in constructing a coding scheme that provides a tradeoff between secret-key and secret-message transmission. The paper [@prabhakaran:09] however does not fully explore the problem of secret key agreement over wiretap channels with state parameters. In particular to the best of our knowledge, it does not have the results in the present paper such as an upper bound on the secret-key capacity, the asymptotic optimality of the lower bound for the Gaussian case or the secret-key capacity for the case of symmetric CSI.

Problem Statement
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Channel 