btcec_malleabilty.go

package main

import (
	"fmt"

	"crypto/sha256"
	"github.com/btcsuite/btcd/btcec"
)

func main() {
	msg := []byte("Then strong encryption became available to the masses, and trust was no longer required.")
	priv, err := btcec.NewPrivateKey(btcec.S256())
	if err != nil {
		panic("Duh!")
	}
	h := sha256.Sum256(msg)

	sig, err := priv.Sign(h[:])
	if err != nil {
		panic("Duh^2!")
	}

	fmt.Println("Signature is valid?", sig.Verify(h[:], priv.PubKey()))
	// s = N - s
	sig.S.Sub(btcec.S256().CurveParams.N, sig.S)

	fmt.Println("'Malleated' Signature is still valid?", sig.Verify(h[:], priv.PubKey()))
}