  We formulate and study a cryptographic problem relevant to wireless: a
sender, Alice, wants to transmit private messages to two receivers, Bob and
Calvin, using unreliable wireless broadcast transmissions and short public
feedback from Bob and Calvin. We ask, at what rates can we broadcast the
private messages if we also provide (information-theoretic) unconditional
security guarantees that Bob and Calvin do not learn each-other's message? We
characterize the largest transmission rates to the two receivers, for any
protocol that provides unconditional security guarantees. We design a protocol
that operates at any rate-pair within the above region, uses very simple
interactions and operations, and is robust to misbehaving users.
