On Thu, 15 Aug 2002, Anonymous wrote:
[Repost]
Joe Ashwood writes:
Actually that does nothing to stop it. Because of the construction of TCPA, the private keys are registered _after_ the owner receives the computer, this is the window of opportunity against that as well.
Actually, this is not true for the endoresement key, PUBEK/PRIVEK, which is the "main" TPM key, the one which gets certified by the "TPM Entity". That key is generated only once on a TPM, before ownership, and must exist before anyone can take ownership. For reference, see section 9.2, "The first call to TPM_CreateEndorsementKeyPair generates the endorsement key pair. After a successful completion of TPM_CreateEndorsementKeyPair all subsequent calls return TCPA_FAIL." Also section 9.2.1 shows that no ownership proof is necessary for this step, which is because there is no owner at that time. Then look at section 5.11.1, on taking ownership: "user must encrypt the values using the PUBEK." So the PUBEK must exist before anyone can take ownership.
The worst case for cost of this is to purchase an additional motherboard (IIRC Fry's has them as low as $50), giving the ability to present a purchase. The virtual-private key is then created, and registered using the credentials borrowed from the second motherboard. Since TCPA doesn't allow for direct remote queries against the hardware, the virtual system will actually have first shot at the incoming data. That's the worst case.
I don't quite follow what you are proposing here, but by the time you purchase a board with a TPM chip on it, it will have already generated its PUBEK and had it certified. So you should not be able to transfer a credential of this type from one board to another one.
< ... /> But I think you claimed "No root key.". Is this not a "root key"? oo--JS.