restFS: Secure data deletion using reliable & efficient stackable file system

Abstract

After deletion data recovery is trivial and can be performed by novice hackers. Secure deletion of data can be achieved by overwriting the file's metadata and user data during its deletion. We propose restFS, a reliable and efficient stackable file system, to fulfill the reliability and efficiency lacking in existing transparent per-file secure data deletion file system extensions. restFS is design compatible with all file systems which export block allocation map of a file to VFS and is currently implemented for EXT2 file system. Instead of overwriting at file level found in existing techniques, restFS overwrites at block level for reliability and efficiency. We evaluated the efficiency of restFS using Postmark benchmark and results indicate that restFS can save 28-98% of block overwrites which otherwise need necessarily to be overwritten in existing overwriting techniques. In addition to this, it can reduce the number of write commands issued to disk by 88%.