Abstract

A method and an apparatus for protecting selected files in a portable computer system. With this invention a user selects a set of riles on a hard disk of the system for protection. This invention uses an encryption key, a secret key and an algorithmic transform to protect the selected files. With this invention the selected files are encrypted with the encryption key, and two copies of the encryption key are scrambled, one with the secret key and one with the transform of the secret key. Then, both scrambled versions of the encryption key are stored on the hard disk. When the user enters the secret key, the two scrambled versions of the encryption key are unscrambled using the key entered by the user and by using the transform of the key entered by the user. These unscrambled versions are then compared. If these unscrambled versions match, the original encryption key has been correctly restored and selected files will be decrypted either immediately or when referenced by an application program. This invention also calls for re-encrypting the selected files upon expiration of a timer indicating that the computer is idle or upon the repeated failure of a user to enter the secret key when requested.