Wiretap Channel with Strictly Causal Side Information at Encoder

In this paper, the wiretap channel with side information studied in [2] is revisited for the case in which the side information is available only at the encoder and in a strictly causal manner. We derive a lower bound on the secrecy capacity of the channel based on a coding scheme which consists of block Markov encoding and key generation using the strictly causal state information available at the encoder. In order to provide the secrecy of messages, at the end of each block a description of the state sequence obtained by the encoder is used to generate the key which encrypts the whole or part of the message to be transmitted in the next block. Moreover, for the decoder to be able to decrypt the messages, the description of the sate sequence of each block is sent in common with the message of that block. Also, an upper bound on the secrecy capacity is developed which assumes that the state is noncausally known at the encoder and we prove that it would coincide the lower bound for a special case and results in the secrecy capacity.