package main

import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/base64"
	"fmt"
)

func HMACSign(payload, key []byte) string {
	mac := hmac.New(sha256.New, key)
	mac.Write(payload)
	return base64.StdEncoding.EncodeToString(mac.Sum(nil))
}

func HMACVerify(payload, key []byte, receivedSig string) bool {
	rMac, err := base64.StdEncoding.DecodeString(receivedSig)
	if err != nil {
		return false
	}

	eMac := hmac.New(sha256.New, key)
	eMac.Write(payload)

	return hmac.Equal(eMac.Sum(nil), rMac)
}

func main() {
	payload := []byte("Conteúdo da mensagem a ser assinada")
	key := []byte("MinhaChaveSecretaSuperSegura")

	signature := HMACSign(payload, key)
	fmt.Println("Assinatura:", signature)

	if HMACVerify(payload, key, signature) {
		fmt.Println("Assinatura válida!")
		return
	}

	fmt.Println("Assinatura inválida!")
}