1 files changed, 25 insertions, 0 deletions
diff --git a/core/src/main/java/org/spongycastle/math/ec/MontgomeryLadderMultiplier.java b/core/src/main/java/org/spongycastle/math/ec/MontgomeryLadderMultiplier.java
new file mode 100644
index 00000000..bc4f7a00
--- /dev/null
+++ b/core/src/main/java/org/spongycastle/math/ec/MontgomeryLadderMultiplier.java
@@ -0,0 +1,25 @@
+package org.spongycastle.math.ec;
+
+import java.math.BigInteger;
+
+public class MontgomeryLadderMultiplier extends AbstractECMultiplier
+{
+    /**
+     * Montgomery ladder.
+     */
+    protected ECPoint multiplyPositive(ECPoint p, BigInteger k)
+    {
+        ECPoint[] R = new ECPoint[]{ p.getCurve().getInfinity(), 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];
+    }
+}