[TrouSerS-users] TPM "secure boot"

[Axelle A. <axe...@ya...>]

Hi all,
this is not 100% related to trousers (sorry) but I'm
quite sure you know...
I'm a little uneasy with the "secure boot"
functionality of TPM. Does this refer to the way the
TPM initializes itself (TPM_Init, TPM_Startup,
TPM_ContinueSelfTests etc) or does this refer to
some
higher level mechanism using PCRs ?

If it's the former, this means "secure boot" is
TPM-dependant. It works the way the manufacturer has
shipped it, and so it only guarantees the "hardware"
is not damaged.
 
If it's the latter, I don't understand how it works.
I've been reading about chain of trusts etc, but
it's
strange because it makes integrity measurements,
that
are stored in the PCR. Okay, but against what does
it
check those PCR values ? Because at each reboot,
PCRs
are zeroed, so how does it know, at the end of the
boot procedure, that PCR value XYZ is correct ?

Thanks for any explanation...
Axelle.



	

	
		
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