In TCFS, security acts in a transparent way. A special flag, which looks like an EXT2 extended attribute, marks encrypted files to make them distinguishable from unencrypted ones. Thus, TCFS is able to store both secure and unsecure files on the same file system depending on whether or not this flag is set. We give special attention to making TCFS completely transparent to the file server. Transparency allows the superuser on a server to perform all administration duties in that we don't change the data structures of the file system itself.
Special work is needed for a directory with the secure flag enabled.
Files in a secure directory are stored with encrypted filenames, and new files inherit the secure flag, so that they too are secure. For this reason, all applications can use the new features without being recompiled. NFS is a simple distributed file system that allows a file system server to export its file systems to several clients. Applications, running on a client, access the remote file system via the usual system calls. The client kernel checks to see whether the requested data is on a local file system or an NFS file system.