  We investigate the delay limited secrecy capacity of the flat fading channel
under two different assumptions on the available transmitter channel state
information (CSI). The first scenario assumes perfect prior knowledge of both
the main and eavesdropper channel gains. Here, upper and lower bounds on the
delay limited secrecy capacity are derived, and shown to be tight in the high
signal-to-noise ratio (SNR) regime. In the second scenario, only the main
channel CSI is assumed to be available at the transmitter where, remarkably, we
establish the achievability of a non-zero delay-limited secure rate, for a wide
class of channel distributions, with a high probability. In the two cases, our
achievability arguments are based on a novel two-stage key-sharing approach
that overcomes the secrecy outage phenomenon observed in earlier works.
