Re: A _good_ and valid use for TPM

[Robert Millan]

On Thu, Feb 19, 2009 at 07:38:36AM -0800, Colin D Bennett wrote:
> 
> While TPM may open a door for corporations to prevent machine owners
> from having control over their machines, in this instance I do not see
> another way to solve Alex's problem.

There's an easy way out of this.  Simply verify data integrity from the
flash chip, and make sure nobody can write to the flash chip.

You can archieve the first by e.g. installing coreboot/GRUB there and
add some crypto support to it.

You can archieve the second by cutting the WE wire, or by dumping lots of
concrete over your board.  Yes, this is a gazillon times more secure than
a TPM.  TPMs are vulnerable to reverse engineering.

> The evil part of TPM seems to be when a person buys a computer but the
> computer is locked down with a key not provided to the buyer.

Precisely.  If it came with a key that is known to the buyer (e.g. printed
on paper), or with an override mechanism that is only accessible to its
legitimate buyer, there would be no problem with it.

But AFAICT there are no TPMs that do this.  It probably even violates the
spec.

-- 
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."