1 files changed, 30 insertions, 0 deletions
diff --git a/core/src/main/java/org/spongycastle/math/ec/ZSignedDigitR2LMultiplier.java b/core/src/main/java/org/spongycastle/math/ec/ZSignedDigitR2LMultiplier.java
new file mode 100644
index 00000000..e9147ea7
--- /dev/null
+++ b/core/src/main/java/org/spongycastle/math/ec/ZSignedDigitR2LMultiplier.java
@@ -0,0 +1,30 @@
+package org.spongycastle.math.ec;
+
+import java.math.BigInteger;
+
+public class ZSignedDigitR2LMultiplier extends AbstractECMultiplier
+{
+    /**
+     * 'Zeroless' Signed Digit Right-to-Left.
+     */
+    protected ECPoint multiplyPositive(ECPoint p, BigInteger k)
+    {
+        ECPoint R0 = p.getCurve().getInfinity(), R1 = p;
+
+        int n = k.bitLength();
+        int s = k.getLowestSetBit();
+
+        R1 = R1.timesPow2(s);
+
+        int i = s;
+        while (++i < n)
+        {
+            R0 = R0.add(k.testBit(i) ? R1 : R1.negate());
+            R1 = R1.twice();
+        }
+
+        R0 = R0.add(R1);
+
+        return R0;
+    }
+}