Re: A _good_ and valid use for TPM

[Robert Millan <rmh@aybabtu.com>]

On Sun, Feb 22, 2009 at 03:26:32AM +0200, Alex Besogonov wrote:
> Robert Millan wrote:
>>> It's exactly what I want to do (minus the 'coercing' part). I want to
>>> ensure that devices run only my unmodified software (which I consider
>>> secure) and only in this case provide decryption keys for sensitive
>>> data. Of course, it done not for DRM purposes, but rather to protect
>>> sensitive data from theft (real theft, not copyright infringement).
>> There's no fundamental difference between hardening a device and using that
>> as your root of trust and using someone else's hardened device and using
>> that as your root of trust.  
> There's a difference. It's impossible to create the root-of-trust  
> without some hardware/firmware support.

I assume you mean a root of trust that's not vulnerable to physical
attack.  Sure, you need firmware support, but you don't need to blindly
trust someone else's firmware when you can use coreboot with GRUB as
your firmware.

>> The only differences are:
>>   - One more link in the trust chain (irrelevant).
>>   - Because it's _someone else's_ computer (the TPM), you're irrationally
>>     assuming that its security is flawless.
> Security of TPM vendors is audited by a third party. For most practical  
> purposes it can be considered quite adequate.

Adequate maybe, not flawless.  And using your own concrete is still cheaper
and more trustworthy than someone else's silicon :-)

-- 
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."