Re: GRUB hardened boot framework

[Robert Millan <rmh@aybabtu.com>]

On Fri, Feb 27, 2009 at 11:55:55PM +0100, phcoder wrote:
>>
>> I'm no crypto expert, but I was under the impression that when the data is
>> encrypted, measurement comes "for free": if someone tampered it, you'd be
>> unable to decrypt.  Is this correct?
>>
> It's not. Encryption is permutation
> E_{key,sector} (P) -> C
> Which permutes transforms plaintext P to ciphertext P. Without knowing  
> the key an attacker still can reuse the values he has already seen (e.g.  
> if he has an image of FS at previous date).
> He can also replace the sector with anything. He can't predict to what  
> it will be decrypted but not to what it originally was

I stand corrected;  But in that case, measurement can still be implemented
at the filesystem level?

-- 
Robert Millan

  The DRM opt-in fallacy: "Your data belongs to us. We will decide when (and
  how) you may access your data; but nobody's threatening your freedom: we
  still allow you to remove your data and not access it at all."