The general class of quantum states which are unconditionally private are introduced. This allows us to consider the production of a secure key within the same paradigm as entanglement theory by making one change -- instead of distilling singlets we distill these private states. It is then shown that an arbitrarily secure key can be distilled from bound entangled states. In general the amount of distillable key is no greater than the relative entropy of entanglement.
- http://arxiv.org/abs/quant-ph/0309110 - paper from arXiv