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In that case, maybe you could do a sort of replay attack? Take a TPM, record a million or so valid states and their signature, and replay those in order every b
by metalcrow 2y ago
In that case, maybe you could do a sort of replay attack? Take a TPM, record a million or so valid states and their signature, and replay those in order every boot? Assuming the TPM is deterministic on startup and you record enough states that you don't have to loop them before reboot, you would have, in effect, a swappable TPM.
Of course, if you get banned then you need to record a new TPM and use that, and that may be difficult.
- utensil4778 2y agoA nonce is a token specifically meant to prevent replay attacks. There's no sane reason to assume TPM is deterministic, as that would defeat the purpose of all the security.
- metalcrow 2y agoYou're right, i somehow skipped over that in reading. And you would want a TPM to be deterministic, after all one major use of the TPM is validating the hardware and boot state is unchanged. Is the state except of the nonce deterministic?
- richbell 2y agoMy understanding is that replay attacks are possible with a TPM, if the consuming logic is flawed. IIRC Microsoft's original implementation of signing Primary Refresh Tokens with TPM was flawed in this way.