SFS doesn't just make a file hard to read -- it conceals the information's existence.
Encryption experts are claiming that a little-known file-hiding process utilising the Steganographic File System (SFS) may enable people to circumnavigate the government's planned method of obtaining private encryption keys.
This snappily named information hiding protocol allows a file to be concealed effectively within another file so that, unless one knows the filename as well as a password, it is impossible to know whether the hidden file even exists.
As the government's plans to confiscate private encryption keys of criminal suspects have emerged in recent weeks, messages extolling SFS' virtues have began to proliferate in news groups such as "ukcrypto".
Steganography is the science of not just protecting the content of a message, but hiding its very existence. Cryptographic and steganographic experts Ross Anderson, Adi Shamir and Roger Needham developed the theory behind the SFS in 1998, and this year two students at Cambridge University developed its first-ever implementation for the Linux operating system.
Caspar Bowden, head of independent government think-tank The Foundation for Information Policy Research (FIPR), and a colleague of Ross Anderson, describes SFS in revolutionary terms. "This is a very elegant and very robust way of hiding data. The whole disk becomes a file system full of data, where there are no blanks, so that you have to know the filename to even find out if a file exists. For the first time it provides plausible deniability because it is impossible to know if you are even hiding information."
Brian Gladman, an independent encryption researcher, admits that this is technology has yet to reach the mainstream, but believes that the UK government's plans on monitoring email could make it commonplace. "If the government introduces the bill that is in draft, it would increase the popularity of this significantly," he says. "To make it really popular, we must get it on Windows. In principle I believe that it would be easier to do it for Windows 2000 because it has an installable file system, unlike 95 and 98."
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