API change to capture "recovery id" during signing about micro-ecc HOT 10 OPEN

Looks like you should be able to just use:

recid = p[curve->num_bytes] & 0x01

at uECC.c:1200 (in the current revision).

Technically you also need to account for overflow mod n, but that will basically never happen.

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Thanks! Do you want a pull request which does that? The problem is I have to change the API.

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Try it out and see if it works for you locally first. I'll think about whether/how to do an API change.

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Hmm. Didn't work. Still gets wrong answer about 50% of the time. I wonder if the "side channel" protection stuff is a factor here.

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OK, I'll look into it in more detail

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My mistake, it should be:

recid = p[num_words] & 0x01;

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Yes. Works great! I should have noticed that.

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+1 for this feature. It's great to have recovery ID.

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It would be great to see this small feature integrated into the API!

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For those who need recid and pubkey recovery feature.
try this trezor's library out, it is btc/eth blockchain friedly.
https://github.com/trezor/trezor-firmware/tree/master/crypto

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