An achievable region of Gaussian wiretap channel with side information

We have proved a coding theorem for the discrete memoryless wiretap channel with side information. Extending the result to the Gaussian case, an achievable rate equivocation region is given by using a strategy similar to Costa's method on dirty paper channel. In this paper, we propose an extended region for the Gaussian wiretap channel with side information. On the other hand, it is well known that, to yield the optimal rate, Costa only considers the situation when the codeword sent by the encoder is independent of side information. Here we will show that, for the wiretap channel, to yield higher rate with the same equivocation, it might be a better choice to send a codeword dependent of side information in some cases.