  We characterize the set of shared quantum states which contain a
cryptographically private key. This allows us to recast the theory of privacy
as a paradigm closely related to that used in entanglement manipulation. It is
shown that one can distill an arbitrarily secure key from bound entangled
states. There are also states which have less distillable private key than the
entanglement cost of the state. In general the amount of distillable key is
bounded from above by the relative entropy of entanglement. Relationships
between distillability and distinguishability are found for a class of states
which have Bell states correlated to separable hiding states. We also describe
a technique for finding states exhibiting irreversibility in entanglement
distillation.
