Method for providing a single level secure (SLS) user processor (402, 502) with access to a multi-level secure (MLS) file system (300). The method begins by authenticating a user to a cryptographic processor (302) by communicating one or more types of user authentication information to the cryptographic processor. Based on such authentication, the MLS file system services are provided such that the SLS user processor (402, 502) has access to files (306, 308, 310, 312, 314) at only one defined security classification level at a time. The method also includes zeroizing one or more data stores used by the SLS user processor each time the SLS user processor transitions between accessing classified data files at a first security classification level and a second security classification level.