(fix) It is not generally safe to mutably multiply a bigint, though i…

…t does work if the number you are multiplying by is big enough (probably because either the result vector is reallocated or you just don't happen to write to a storage location before you've finished reading it). (#121)

schnorr/schnorr.go

@@ -67,8 +67,8 @@ func TrySign(privateKey []byte, publicKey []byte, message []byte, k []byte) ([]b
 
 	//4. Compute s = k - r * prv
 	// 4a. Compute r * prv
-	_r := *r
-	s := new(big.Int).Mod(_r.Mul(&_r, priKey), keytools.Secp256k1.N)
+	var v = new(big.Int).Mul(r, priKey)
+	s := new(big.Int).Mod(v, keytools.Secp256k1.N)
 	s = new(big.Int).Mod(new(big.Int).Sub(bintK, s), keytools.Secp256k1.N)
 
 	if s.Cmp(big.NewInt(0)) == 0 {