Re: [PATCH] Delete cryptoloop

[Fruhwirth Clemens <clemens-dated-1091653086.2b8e@endorphin.org>]

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On Sun, 2004-07-25 at 21:44, Marc Ballarin wrote:
> Fruhwirth Clemens <clemens-dated-1091642568.f246 <at> endorphin.org> writes:  
>   
> >   
> > Probably I'm missing the point, but at the moment this looks like a  
> > chosen plain text attack. As you know for sure, this is trivial. For  
> > instance, AES asserts to be secure against this kind of attack. (See the  
> > author's definition of K-secure..).  
>   
> It assures against key revovery through chosen plain text attacks. As written 
> before, the purpose of this attack is not to break encryption, but to prove 
> the existence of a file *known to* and *prepared by* the attacker.  

If an attacker has some means to put a file on the encrypted hard disk,
I'm not considering it a big breakthrough if he can find out the
position of that file. I'm sure this information can be gained by
forensic block access pattern analysis anyway.

> The exploit generates a rather simple bit pattern with a size of 1024 bytes.  
> When this pattern - the watermark - is encrypted, dm-crypt's output has some  
> special properties - independent of cipher or key size.  
> For example, encoding nr. 1, always produces a cyphertext block, where bytes  
> 0-15 are equal to bytes 512-523.  

I'm starting to wonder why this is called an attack. The results of this
``attack'' can't be used in any way. In the worst case, a cipher
text/plain text pair can be obtained. I'm repeating it one more time:
ciphers are designed to resist further attacks steaming from known-plain
text attacks.

Have a look at 
http://clemens.endorphin.org/OnTheProblemsOfCryptoloop . That's an
attack!
  
> On dm-crypt's mailing list, I have given a description how this can be refined  
> easily to improve reliability of detection and determine a file's layout on 
> the encrypted volume.  

I'm sorry, I consider this useless information. 

-- 
Fruhwirth Clemens <clemens@endorphin.org>  http://clemens.endorphin.org

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