Replying to Avatar frphank

> they export the key to the insecure MCU once the boot is complete

Why would they do that? An SE can sign on-chip which is its very purpose. Can you point me to the code in any open source firmware implementation where that happens?

I don't even believe SEs have functionality to export persistent keys.
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semisol 2mo ago

They use an authenticated data storage slot.

All of the ones using ATECC series do this. It has data storage slots & a few ECC key slots. Of course it’s P-256 only (not secp256k1) and only supports signing, so you get this.

Same thing with Infineon Optiga based ones which can’t do the required algorithms for Bitcoin but can at least keep more types of keys on SE.

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frphank 2mo ago

Oww #btcfail. Satoshi had to have his funky off-beat curve for no other reason than to be funky.

SE050 does secp256k1 afaik so no excuses there.

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semisol 2mo ago

BIP-32 and Schnorr not supported without a hack.

The choice of secp256k1 is at least better than the turd that is NIST curves.