One embodiment of the present invention relates to a system for managing files which facilitates making the files permanently unreadable. During operation, the system maintains file-class keys at a file manager, wherein the file-class keys are associated with different classes of files. If a file belongs to a class of files, the system ensures that whenever the file is stored or updated in non-volatile storage that the file is encrypted with an associated key-manager-file-class key for the class of files. The system makes an entire class of files permanently unreadable by causing an associated key-manager-file-class key, which can be used to decrypt the class of files, to become permanently unreadable.