Re: [Trustedjava-support] Questions about PCR quoteing (Attestation)

[Martin P. <Mar...@ia...>]

dev...@ar... wrote:
> System A communicates with System B for the first time
> For my understanding system B cannot check the signed PCR at this time as well as it cannot check the nonce, because of it does not know the expected values.

The point of using a nonce is to provide freshness, a random nonce
cannot be predicted and thus makes certain attacks (e.g. replay)
harder.

One entity requests a quote and provides a nonce, the other does
the quote and then, by examining the nonce in the response one
can be assured the quote was done "just now" - it is a freshly
generated reply.

> 3. Are the checks, which were described int the scenario are enough for attestation?

What is the point of each check?

nonce -> provides evidence that the answer is fresh
PCRs content -> provides evidence of system state
signature on PCRs -> cryptographic binding of PCR info to key
AIK certificate -> proof that the key is really a hardware
 TPM hosted non-migrateable identity key
...and a PKI is needed to manage/validate AIK certificates
according to a specific policy, trusted to be done correctly
by the application

HTH,
Martin