feat: add coincurve instead of secp256k1

[dni]

• changed secp256k1 to coincurve
• add testcase for verifying pubkey missing bolt11 example where n field must be verified by reader lightning/bolts#1184
• added keep_payee flag for encoding
• added tests for signature model
• added test for invalid signature

[prusnak]

Can you also try to remove ecdsa from dependencies and rewrite its usage with coincurve? Should be possible

[motorina0]

LGTM

see comments

[prusnak]

Can you also try to remove ecdsa from dependencies and rewrite its usage with coincurve? Should be possible

Hm, it seems that coincurve does not provide an easy way how to use a signature in hex-string format (not DER).

We could use the following to convert hex-string sig to DER, but it does not help us with getting rid of the dependency :-/

from ecdsa import SECP256k1
from ecdsa.util import sigdecode_string, sigencode_der_canonize

r, s = sigdecode_string(signature_data, SECP256k1.order)
der_sig = sigencode_der_canonize(r, s, SECP256k1.order)

[dni]

Can you also try to remove ecdsa from dependencies and rewrite its usage with coincurve? Should be possible

Hm, it seems that coincurve does not provide an easy way how to use a signature in hex-string format (not DER).

We could use the following to convert hex-string sig to DER, but it does not help us with getting rid of the dependency :-/

from ecdsa import SECP256k1
from ecdsa.util import sigdecode_string, sigencode_der_canonize

r, s = sigdecode_string(signature_data, SECP256k1.order)
der_sig = sigencode_der_canonize(r, s, SECP256k1.order)

yep, took me a bit to figure it out.

        sig = deserialize_recoverable(self.signature_data)
        sig = recoverable_convert(sig)
        sig = cdata_to_der(sig)
        if not verify_signature(
            sig, message(self.hrp, self.signing_data), bytes.fromhex(payee)
        ):
            raise ValueError("Invalid signature")