BIP 322 P2WPKH BIP322 Verification in Go

bip322.go

package main

import (
	"encoding/base64"
	"log"

	"github.com/btcsuite/btcd/btcutil"
	"github.com/btcsuite/btcd/chaincfg"
	"github.com/btcsuite/btcd/txscript"
	"github.com/btcsuite/btcd/wire"

	bip322 "github.com/unisat-wallet/libbrc20-indexer/utils/bip322"
)

func convertAddressToScriptPubkey(address string) []byte {
	btcAddress, err := btcutil.DecodeAddress(address, &chaincfg.MainNetParams)
	if err != nil {
		panic(err)
	}

	outputScript, err := txscript.PayToAddrScript(btcAddress)
	if err != nil {
		panic(err)
	}

	return outputScript
}

func main() {
	//You can replace these with the actual values you want to verify
	//These are in the format used by bip322-js
	//This is for P2WPKH BIP322 verification
	message := "Hello World"
	signature := "AkcwRAIgZRfIY3p7/DoVTty6YZbWS71bc5Vct9p9Fia83eRmw2QCICK/ENGfwLtptFluMGs2KsqoNSk89pO7F29zJLUx9a/sASECx/EgAxlkQpQ9hYjgGu6EBCPMVPwVIVJqO4XCsMvViHI="
	signerAddress := "bc1q9vza2e8x573nczrlzms0wvx3gsqjx7vavgkx0l"

	//These will be in the following format:
	//[0x02 or 0x03] [LENGTH_BYTE, ...(LENGTH bytes that go into witness[0])] [0x21, ...(33 byte (len = 0x21) public key that was used to sign the message)]
	//- First byte is either a 0x02 or 0x03 (not sure exactly why but apparently it is - https://github.com/ACken2/bip322-js/blob/f0f9373b3a1da19e017c518b891522eaa4bcccdd/src/helpers/Address.ts#L85)
	//- Next part is the details that go into witness[0] (length of this part is determined by the second byte) - again, not exactly sure what this is
	//- Last part is the public key that was used to sign the message (33 bytes) - There is a length byte 0x21 before this part to denote the length of the public key (0x21 = 33)
	encodedSigBytes, err := base64.StdEncoding.DecodeString(signature)
	if err != nil {
		panic(err)
	}

	//Convert the address to a public key script (I believe this is the denotation for a pay-to-this-address script but not 100% sure)
	pkScript := convertAddressToScriptPubkey(signerAddress)

	//Decode the length of the witness[0] part
	encodedSigLenByte := encodedSigBytes[1]
	encodedSigLen := int(encodedSigLenByte)

	//Extract witness[0] and witness[1] from the encoded signature
	PUB_KEY_LEN := 33
	encodedSig := encodedSigBytes[len(encodedSigBytes)-PUB_KEY_LEN-1-encodedSigLen : len(encodedSigBytes)-PUB_KEY_LEN-1]
	pubKey := encodedSigBytes[len(encodedSigBytes)-33:]

	//Recreate the witness to pass into the VerifySignature function
	witness := wire.TxWitness{
		encodedSig,
		pubKey,
	}

	//This is the BIP322 verification function from the Unisat wallet
	verified := bip322.VerifySignature(witness, pkScript, message)
	log.Println("BIP 322 Verified:", verified)
}