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by AviKav 1372 days ago
> A user- or host-supplied secret can also be mixed into the key derivation function

To clarify, this secret does not affect the program's hash, right? (e.g. to prove liveness, the parameter is a nonce to be signed with a deterministic private key)
1 comments
JoachimS 1372 days ago
No, the USS would be used (mixed in as kfreds stated) during the hash operation. So the hash result would be based in (1) the hash of the application, (2) the unique device secret, and (3) the user supplied secret. The result is called Compound Device Identity in DICE parlance. And is basically

CDI = Hash(UDS, Hash(application) + USS)

If the application would use the result (called CDI - Compound Device Identity in DICE parlance) to derive a pair of keys, the keys would thus be based on the hardware (the specific device you have), the integrity of the application and what you know.

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