Re: TPM support status ?

[Michael Gorven]

On Wed, Aug 19, 2009 at 08:48:13PM +0200, Vladimir 'phcoder' Serbinenko wrote:
> > Since the BIOS can be "easily" replaced, it cannot be trusted, hence you
> > can't build a chain of trust starting from your BIOS. It is a "little"
> > more difficult to replace a TPM, even more if it's holding a shared
> > secret. :)
> Write wire? Concrete around the chip? Concrete is more resistant than
> silicon as last studies have shown.

99% of people with this use case are not going to put their BIOS chip in 
concrete. Configuring a TPM chip a lot easier.

> > I keep trusting it because
> > the TPM tells me it hasn't been altered on my computer by nasty people.
> Suppose even that TPM or XYZ can ensure software isn't tampered at
> all. Attacker can alter your hardware instead. It just changes the way
> your computer is attacked, not the result. As a matter of fact
> hardware attacks are now more widespread in these considerations.

Yes -- the whole point is to make it more difficult and require more 
resources.

> > > TPM claims to e.g. protect your hd encryption keys. But what a hacker
> > > would do is to boot computer, wait that it retrieves the keys and then
> > > execute cold boot attack (in most cases it's enough to just cool RAM
> > > down and reboot with a USB key which will dump the memory). I don't
> > > spend my time on implementing a "security" which increases hacking
> > > cost by $15, claims to be unbreakable and can be used for evil
> > > purposes (in which case it's more difficult to crack)
> >
> > Uh, wait! There's something I don't understand there. What's the point
> > in puting the whole secret in the TPM? It's like writing your passphrase
> > on a paper and put it under your keyboard. A clever implementation would
> > be using the ownership capabilities of the TPM so that the secret can be
> > protected by system integrity _and_ password.
> Then I wait that you enter you password and leave machine unattended
> and execute my cold boot attack. If you never left machine unattended
> you don't need a chip to ensure the integrity.

That's a completely different issue which you don't have a solution to 
either.

-- http://michael.gorven.za.net/
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