Re: rootkit and 10 minutes ?

["Michael T. Babcock" <mbabcock@fibrespeed.net>]

Jean-Luc Cooke wrote:

>If someone can use the fs structure (aka. known plaintext attack) then the
>cipher is broken outright.  So your argument seems lost.
>  
>

What you seemed to be presenting is this:

keysystem <-> kernel fs driver <-> userspace fs display

What I proposed is this:

keysystem <-> userspace crypto (loopback) <-> kernel fs driver <-> 
userspace fs display

The difference is simply that in my version, the data is en/decrypted 
outside the kernel.  In both versions, I have to assume that an attacker 
can, for a much lower budget than crypanalysis, remove the hard drive 
and start playing with it in another machine with a different kernel.  I 
also have to assume that they could have written any number of known 
plaintexts to the drive before doing so.  My version may seem to 
facilitate such work, but in fact the time / effort requirement 
presented by your version still seems trivial compared to a full-scale 
cryptanalytic attack.

I would be much more impressed by a userspace DRM-style crypto system 
that did the crypto work in a library directly accessed by the userspace 
programs trying to deal with the disk files.  Doing an 
"open('blah.txt')" should call a library function that checks for 
'blah.txt' in the current virtual directory of 
/var/hahayoucantreadthis.dat, tries to decrypt it using the current key 
(also read directly by the library into secure memory space) and 
displays / works with it.  Encryption work would similarly happen before 
any other process got its grubby little hands on my bits & bytes.

Just FYI ...

-- 
Michael T. Babcock
C.T.O., FibreSpeed Ltd.
http://www.fibrespeed.net/~mbabcock


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