Ext3cow implements secure deletion, authenticated encryption, and incremental authentication.

"Ext3cow is an open-source, versioning file system based on ext3. It provides a time-shifting interface that allows a real-time and continuous view of the past. This allows users to access their file system as it appeared at any point in time. Ext3cow was designed as a platform for regulatory compliance, and has been used to implement secure deletion, authenticated encryption, and incremental authentication."

Some advantages of ext3cow:
- It does not pollute the name space with named versions
- It has low storage and performance overhead
- It is totally modular, requiring no changes to kernel or VFS interfaces


http://www.ext3cow.com/