  We consider a block fading wiretap channel, where a transmitter attempts to
send messages securely to a receiver in the presence of a hybrid half-duplex
adversary, which arbitrarily decides to either jam or eavesdrop the
transmitter-to- receiver channel. We provide bounds to the secrecy capacity for
various possibilities on receiver feedback and show special cases where the
bounds are tight. We show that, without any feedback from the receiver, the
secrecy capacity is zero if the transmitter-to-adversary channel stochastically
dominates the effective transmitter-to-receiver channel. However, the secrecy
capacity is non-zero even when the receiver is allowed to feed back only one
bit at the end of each block. Our novel achievable strategy improves the rates
proposed in the literature for the non-hybrid adversarial model. We also
analyze the effect of multiple adversaries and delay constraints on the secrecy
capacity. We show that our novel time sharing approach leads to positive
secrecy rates even under strict delay constraints.
