1 research outputs found
Shannon's secrecy system with informed receivers and its application to systematic coding for wiretapped channels
Shannon's secrecy system is studied in a setting, where both the legitimate
decoder and the wiretapper have access to side information sequences correlated
to the source, but the wiretapper receives both the coded information and the
side information via channels that are more noisy than the respective channels
of the legitmate decoder, which in turn, also shares a secret key with the
encoder. A single--letter characterization is provided for the achievable
region in the space of five figures of merit: the equivocation at the
wiretapper, the key rate, the distortion of the source reconstruction at the
legitimate receiver, the bandwidth expansion factor of the coded channels, and
the average transmission cost (generalized power). Beyond the fact that this is
an extension of earlier studies, it also provides a framework for studying
fundamental performance limits of systematic codes in the presence of a wiretap
channel. The best achievable performance of systematic codes is then compared
to that of a general code in several respects, and a few examples are given