  A quantum password is a quantum mechanical analogue of the classical
password. Our proposal is completely quantum mechanical in nature, i.e. at no
point is information stored and manipulated classically. We show that, in
contrast to quantum protocols that encode classical information, we are able to
prevent the distribution of reusable passwords even when Alice actively
cooperates with Eve. This allows us to confront and address security issues
that are unavoidable in classical protocols.
