SFS provides transparent work with encrypted files and protects your data even when stolen with your hard drive.
It works on top of a normal filesystem and using its own library redirects all requests for work with encrypted files to special daemon that takes care of encryption and decryption of files and of user and key management.
SFS is distributed under GNU GPL and you can download it as a RPM package, SRPM package or tgz package.
You can browse the programmer's documentation.
Basic idea of how SFS works you can obtain from these two schemes:
For more information on SFS see README. There are several other documentation files available: