How to replicate signatures from other implementations / verify correctness?

I’m looking for a Python library for ECDSA. I need to match the output of projects in other languages using different libraries for ECDSA. I took some known (key, message, signature) “test vectors” from this ECDSA library in Go and was able to replicate them (or at least the first and fourth) with elliptic in JavaScript, to verify that they work the same. However, I can’t seem to do the same with fastecdsa.

How would you write a function that, given two 32-byte bytes values for both the key and the message digest, returns a DER-encoded bytes signature? I tried this (paraphrased):

from fastecdsa import curve, ecdsa

def sign(private_key_bytes: bytes, message_digest_bytes: bytes) -> bytes:
    private_key = int.from_bytes(private_key_bytes, byteorder='big')
    r, s = ecdsa.sign(
        message_digest_bytes.hex(), private_key, curve=curve.secp256k1, prehashed=True
    )
    r_bytes = r.to_bytes(32, byteorder='big')
    s_bytes = s.to_bytes(32, byteorder='big')
    # Hacky hard-coded DER encoding that works for the two cases I'm testing.
    return b'\x30\x44' + b'\x02\x20' + r_bytes + b'\x02\x20' + s_bytes

You can see it failing on the two test vectors I copied from the Go project.

[thejohnfreeman]

I can confirm v2.1.2 let me replicate signatures. Thank you!

[thejohnfreeman]

Indeed. You can see my IdentityHash here.