  The covert capacity is characterized for a non-coherent fast Rayleigh-fading
wireless channel, in which a legitimate user wishes to communicate reliably
with a legitimate receiver while escaping detection from a warden. It is shown
that the covert capacity is achieved with an amplitude-constrained input
distribution that consists of a finite number of mass points including one at
zero and numerically tractable bounds are provided. It is also conjectured that
distributions with two mass points in fixed locations are optimal.
