1 files changed, 25 insertions, 0 deletions
diff --git a/crypto/src/math/ec/multiplier/MontgomeryLadderMultiplier.cs b/crypto/src/math/ec/multiplier/MontgomeryLadderMultiplier.cs
new file mode 100644
index 000000000..e2470a383
--- /dev/null
+++ b/crypto/src/math/ec/multiplier/MontgomeryLadderMultiplier.cs
@@ -0,0 +1,25 @@
+namespace Org.BouncyCastle.Math.EC.Multiplier
+{
+    public class MontgomeryLadderMultiplier 
+        : AbstractECMultiplier
+    {
+        /**
+         * Montgomery ladder.
+         */
+        protected override ECPoint MultiplyPositive(ECPoint p, BigInteger k)
+        {
+            ECPoint[] R = new ECPoint[]{ p.Curve.Infinity, p };
+
+            int n = k.BitLength;
+            int i = n;
+            while (--i >= 0)
+            {
+                int b = k.TestBit(i) ? 1 : 0;
+                int bp = 1 - b;
+                R[bp] = R[bp].Add(R[b]);
+                R[b] = R[b].Twice();
+            }
+            return R[0];
+        }
+    }
+}