Single-use authentication methods for accessing encrypted data stored on a protected volume of a computer are described, wherein access to the encrypted data involves decrypting a key protector stored on the computer that holds a volume-specific cryptographic key needed to decrypt the protected volume. Such single-use authentication methods rely on the provision of a key protector that can only be used once and/or that requires a new access credential for each use. In certain embodiments, a challenge-response process is also used as part of the authentication method to tie the issuance of a key protector and/or access credential to particular pieces of information that can uniquely identify a user.