Enhancing Secrecy Rates in a wiretap channel
This work addresses secure communication in wiretap channels, offering incremental improvements to mitigate rate losses for applications in wireless security.
The paper tackles the problem of reduced secrecy rates in wiretap channels by proposing a coding scheme using old messages as keys, proving security for multiple messages and achieving strong security. It shows that with full channel state information of the eavesdropper's channel, secrecy capacity can approach the Shannon capacity of the main channel, and extends this to cases with only distributional knowledge.
Reliable communication imposes an upper limit on the achievable rate, namely the Shannon capacity. Wyner's wiretap coding, which ensures a security constraint also, in addition to reliability, results in decrease of the achievable rate. To mitigate the loss in the secrecy rate, we propose a coding scheme where we use sufficiently old messages as key and for this scheme prove that multiple messages are secure with respect to (w.r.t.) all the information possessed by the eavesdropper. We also show that we can achieve security in the strong sense. Next we consider a fading wiretap channel with full channel state information of the eavesdropper's channel and use our coding/decoding scheme to achieve secrecy capacity close to the Shannon capacity of the main channel (in the ergodic sense). Finally we also consider the case where the transmitter does not have the instantaneous information of the channel state of the eavesdropper, but only its distribution.