  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.
