Classical secret information lies on a slippery slope between public information and quantum information. Even leaving aside fanciful attacks like neutrino tomography, a typical classical secret---say a paper document locked in a safe---quickly decoheres and becomes recoverable in principle from the environment outside the safe. On the other hand, if a system is so well insulated from its environment that it does not decohere, it can be used as a quantum memory, capable of existing in a superposition of classical states and of being entangled with other other quantum memories. We discuss the practical and theoretical difficulty of recovering a classical secret from its decohered environment, and of protecting a classical secret by arranging that some information required to recover it escapes into parts of the environment inaccessible to the eavesdropper.