Bug: Monocypher verification of signature fails

[mchack-work]

Verification of an ed25519 signature with the monocypher crypto_ed25519_check() seems to fail, unless I did something wrong.

Fails on both real hardware (red LED) and qemu.

Did we implement some memory function in tkey-libs wrong?

See branch test-verification for a test version of the signer:

https://github.com/tillitis/tkey-device-signer/tree/test-verification

[dehanj]

@LoupVaillant Since you start to dig deeper using the TKey and since you are the author of Monocypher, I just wanted to give you an heads up that we have found this bug. It is most probably on our side, but maybe you have seen something similar before?

We haven't had the time to investigate it further, the plan is to put our attention to it in end of October.
Mostly didn't want you to run into it, if you plan to do verification on the TKey.

[LoupVaillant]

@dehanj, I’ll take a look, thanks for the notification. I was just wondering what to work on next, this looks like a good candidate.