  The Encrypted File System (EFS) pushes encryption services into the file
system itself. EFS supports secure storage at the system level through a
standard UNIX file system interface to encrypted files. User can associate a
cryptographic key with the directories they wish to protect. Files in these
directories (as well as their pathname components) are transparently encrypted
and decrypted with the specified key without further user intervention; clear
text is never stored on a disk or sent to a remote file server. EFS can use any
available file system for its underlying storage without modifications,
including remote file servers such as NFS. System management functions, such as
file backup, work in a normal manner and without knowledge of the key.
Performance is an important factor to users since encryption can be time
consuming. This paper describes the design and implementation of EFS in user
space using faster cryptographic algorithms on UNIX Operating system.
Implementing EFS in user space makes it portable and flexible; Kernel size will
also not increase resulting in more reliable & efficient Operating System.
Encryption techniques for file system level encryption are described, and
general issues of cryptographic system interfaces to support routine secure
computing are discussed.
