How to verify that a signature was signed by a pubkey? Taproot and BIP0322

Question

Using wallets like XVerse, users can sign a message using their ordinal btc address, let's say bc1XXX, the message is hashed based on BIP0322.

So I have:

• User wallet: bc1XXX
• Message hash: YYY
• Signature signed by bc1XXX: ZZZ

So this data is sent to my backend server, and I want to verify that ZZZ was indeed signed by bc1XXX (and contains YYY as message).

I'm using this so far:

    const msgHash = bip0322Hash(message);
    const signatureBuffer = Buffer.from(signatureStr, 'base64');

    const decodedSignature = signatureBuffer.slice(2, 66);
    const recoveryId = signatureBuffer[0];

    // Extract public key from the signature
    const recoveredPublicKeyBuffer = secp.recoverPublicKey(
        msgHash,
        decodedSignature,
        recoveryId, // Recovery ID (0 or 1)
        false
    );
    console.log(publicKeyToTaprootAddress(recoveredPublicKeyBuffer)); //no match with my original pubkey that signed the message

But I have a hard time getting the correct address from recoveredPublicKeyBuffer which I can't match with the public key address of my test set.

I'm trying to use this function, but the output doesn't match my pubkey:

    function publicKeyToTaprootAddress(publicKey: Uint8Array) {
        // Compute the SHA-256 hash of the public key
        const hash = sha256(Buffer.from(publicKey));

        // Construct the human-readable part and the data part of the Bech32m string
        const hrp = 'bc';
        const data = sha256(Buffer.from([0x01].concat(Array.from(hash))));
        const data2 = bech32m.toWords(Buffer.from(data));

        // Encode the Bech32m string
        return bech32m.encode(hrp, data2);
    } 

Answer 1

Assuming that recoverPublicKey is performing the ECDSA key recovery, this does not apply to BIP340 Schnorr Signatures. If you want to use BIP322 with Taproot addresses, you need the original public key.