From 799844d19cf8a66028f3f74e0896ad79ae8d07fb Mon Sep 17 00:00:00 2001
From: Ian Tan <iantanwx@gmail.com>
Date: Thu, 30 May 2019 17:22:54 +0800
Subject: [PATCH] Ensure that R and S are not gte curve order

---
 LaksaCsharp/Crypto/Schnorr.cs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/LaksaCsharp/Crypto/Schnorr.cs b/LaksaCsharp/Crypto/Schnorr.cs
index 7eb555f..d288521 100644
--- a/LaksaCsharp/Crypto/Schnorr.cs
+++ b/LaksaCsharp/Crypto/Schnorr.cs
@@ -135,6 +135,10 @@ public static bool Verify(byte[] msg, Signature sig, ECPoint publicKey)
                 throw new Exception("Invalid R or S value: cannot be negative.");
             }
 
+            if (sig.R.CompareTo(secp256k1.Curve.Order) >= 0 || sig.S.CompareTo(secp256k1.Curve.Order) >= 0) {
+                throw new Exception("Invalid R or S value: must be smaller than curve order");
+            }
+
             if (publicKey.Curve != (secp256k1.Curve))
             {
                 throw new Exception("The public key must be a point on secp256k1.");