data encryption - was Re: [plug] protecting a tar file

[Bill Kenworthy]

Basicly, encrypt a file and write 5 copies of each block to specially
chosen unallocated blocks in the file system using the driver to keep
track of where they are.  Due to the methods used, you need the keys to
descramble the actual location of the data on the disk, and the means to
reassemble them into the correct order (you can apparently have "layers"
of storage to further hide the locations.  Of course encrypted data
looks essentially random in the FS unless you prefill it with zeros or
something.  There are statistical techniques that can reveal the
likelyhood of a FS containg steganographic data, but not extracting it
without the keys as far as I know.

Downside is the OS (can be used on you main fs's as well) will write to
what it thinks is an unallocated sector, so you can lose data easily
(hence 5 copies in statistically chosen areas that are unlikely to be
overwritten)  Dont use for data that you cant risk losing!  But then, if
its important enough to go for this type of thing, its a risk you might
be willing to take.

Somewhat similar to using steganographic systems to hide data in images.

BillK


On Thu, 2004-07-01 at 10:31, Denis Brown wrote:
> On the ways of preventing the exposure of the contents of a tar file, if it 
> fell into the wrong hands...
...
> Stegfs, eh?   "StegFS - A Steganographic File System for Linux"   I'd not 
> heard of that before.   More reading to do but this looks very interesting 
> especially to those of us in the medical / human-data-sensitive 
> fields.   Reference url:  http://www.mcdonald.org.uk/StegFS/   They seem to 
> claim it is not for 2.4 kernels.
> 
> Cheers,
> Denis
> 
> 
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