Example of verifying a ethereum signature from a signed message in Go. Returns the signers address.

verify_eth_sig.go

package main

import (
	"fmt"

	"github.com/ethereum/go-ethereum/crypto"
	"github.com/go-ethereum/common/hexutil"
)

func main() {
	sig := hexutil.MustDecode(
		"0xb79ef6e60652a547eda5b873ee846244ac294814bb4f15b24845ba93f5f5a5224faa295a885d7b08da327e3b884a7a436c45bb6471d02e0331a8f17a768042511b",
	)

	if len(sig) != 65 {
		panic(fmt.Errorf("signature must be 65 bytes long"))
	}

	if sig[64] != 27 && sig[64] != 28 {
		panic(fmt.Errorf("invalid Ethereum signature (V is not 27 or 28)"))
	}
	sig[64] -= 27 // Transform yellow paper V from 27/28 to 0/1

	msg := "\x19Ethereum Signed Message:\n5Login"

	data := crypto.Keccak256([]byte(msg))

	rpk, err := crypto.Ecrecover(data, sig)
	if err != nil {
		panic(err)
	}

	pubKey := crypto.ToECDSAPub(rpk)
	recoveredAddr := crypto.PubkeyToAddress(*pubKey)

	fmt.Printf("0x%x\n", recoveredAddr)
}