Steganographic file system
Steganographic file systems are a kind of file system first proposed by Ross Anderson, Roger Needham, and Adi Shamir. Their paper proposed two main methods of hiding data: in a series of fixed size files originally consisting of random bits on top of which 'vectors' could be superimposed in such a way as to allow levels of security to decrypt all lower levels but not even know of the existence of any higher levels, or an entire partition is filled with random bits and files hidden in it.
In a steganographic file system using the second scheme,
Advantage
While there may seem to be no point to a file system which is guaranteed to either be grossly inefficient storage space-wise or to cause data loss and corruption either from data collisions or loss of the
Criticisms
Poul-Henning Kamp has criticized the threat model for steganographic file systems in his paper on GBDE,[1] observing that in certain coercive situations, especially where the searched-for information is in fact not stored in the steganographic file systems, it is not possible for a subject to "get off the hook" by proving that all keys have been surrendered.
Other methods
Other methods exist; the method laid out before is the one implemented by
Generally, a steganographic file system is implemented over a steganographic layer, which supplies just the storage mechanism. For example, the steganographic file system layer can be some existing MP3 files, each file contains a chunk of data (or a part of the file system). The final product is a file system that is hardly detected (depending on the steganographic layer) that can store any kind of file in a regular file system hierarchy.
TrueCrypt allows for "hidden volumes" - two or more passwords open different volumes in the same file, but only one of the volumes contains secret data.
See also
- Steganography
- Steganography tools
- BPCS-Steganography
- Filesystem-level encryption
References
- ^ Poul-Henning Kamp. "GBDE - GEOM Based Disk Encryption" (PDF). GBDE Design Document.
External links
- Original paper by Anderson, Needham, et al. -(PDF file)
- A MP3 Steganographic File System Approach
- MagikFS - The Steganographic FileSystem
- StegFS - A Steganographic File System Without Data Losing Problems
- StegHide - Hiding Data Accesses in Steganographic File Systems
- Xuan Zhou's Ph.D. Thesis on Steganographic File System