Optimized Sqrt() for custom secp224r1

1 files changed, 26 insertions, 0 deletions

diff --git a/crypto/src/math/ec/Mod.cs b/crypto/src/math/ec/Mod.cs

index a05ff77aa..37958e57e 100644
--- a/crypto/src/math/ec/Mod.cs
+++ b/crypto/src/math/ec/Mod.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Diagnostics;
 
+using Org.BouncyCastle.Crypto.Utilities;
 using Org.BouncyCastle.Utilities;
 
 namespace Org.BouncyCastle.Math.EC
@@ -73,6 +74,31 @@ namespace Org.BouncyCastle.Math.EC
             }
         }
 
+        public static uint[] Random(uint[] p)
+        {
+            int len = p.Length;
+            Random rand = new Random();
+            uint[] s = Nat.Create(len);
+
+            uint m = p[len - 1];
+            m |= m >> 1;
+            m |= m >> 2;
+            m |= m >> 4;
+            m |= m >> 8;
+            m |= m >> 16;
+
+            do
+            {
+                byte[] bytes = new byte[len << 2];
+                rand.NextBytes(bytes);
+                Pack.BE_To_UInt32(bytes, 0, s);
+                s[len - 1] &= m;
+            }
+            while (Nat.Gte(len, s, p));
+
+            return s;
+        }
+
         public static void Subtract(uint[] p, uint[] x, uint[] y, uint[] z)
         {
             int len = p.Length;