Contructing a PublicKey with rawRepresentation fails with incorrect size about secp256k1.swift

[csjones]

Hey @pseudoramdom

You're correct, pubkeyHex does seem to be a x-only key. Maybe I'm misunderstanding what you're trying to accomplish but I don't think it makes sense to always pad a pubkeyHex with a [3] because the key's parity determines whether it should be padded with a [2] or [3]. Here is a thread about an approach bitcoin-core/secp256k1#1097

More recent versions of this package started the initial work to handle this conversion, looks like this:

let pubkeyHex = "11cc106e72c654b64bb037d0ccbe2ff47187fa5bb77330dd70398c2cb051fbd6"
let xonlyKey = try! secp256k1.Signing.XonlyKey(rawRepresentation: pubkeyHex.bytes, keyParity: 1)

This requires knowing the key's parity to correctly pad the public key automatically. I'd like to get to the ideal usage of:

let pubkeyHex = "11cc106e72c654b64bb037d0ccbe2ff47187fa5bb77330dd70398c2cb051fbd6"
let xonlyKey = try! secp256k1.Signing.XonlyKey(rawRepresentation: pubkeyHex.bytes)

Once we have a XonlyKey object, creating a secp256k1.Signing.PublicKey is simply one more line:

let pubkeyHex = "11cc106e72c654b64bb037d0ccbe2ff47187fa5bb77330dd70398c2cb051fbd6"
let xonlyKey = try! secp256k1.Signing.XonlyKey(rawRepresentation: pubkeyHex.bytes)
let pubKey = try! secp256k1.Signing.PublicKey(xonlyKey: xonlyKey)

[pseudoramdom]

Got it. Thanks for clarifying. Much appreciated.

[pseudoramdom]

(not a cryptography expert) I believe my pubkeyHex is an xOnlyKey. So I had to pad it with a [3] similar to https://github.com/GigaBitcoin/secp256k1.swift/pull/239/files