1 files changed, 29 insertions, 0 deletions
diff --git a/libraries/spongycastle/core/src/main/java/org/spongycastle/math/ec/ZSignedDigitL2RMultiplier.java b/libraries/spongycastle/core/src/main/java/org/spongycastle/math/ec/ZSignedDigitL2RMultiplier.java
new file mode 100644
index 000000000..543bb581f
--- /dev/null
+++ b/libraries/spongycastle/core/src/main/java/org/spongycastle/math/ec/ZSignedDigitL2RMultiplier.java
@@ -0,0 +1,29 @@
+package org.spongycastle.math.ec;
+
+import java.math.BigInteger;
+
+public class ZSignedDigitL2RMultiplier extends AbstractECMultiplier
+{
+    /**
+     * 'Zeroless' Signed Digit Left-to-Right.
+     */
+    protected ECPoint multiplyPositive(ECPoint p, BigInteger k)
+    {
+        ECPoint addP = p.normalize(), subP = addP.negate();
+
+        ECPoint R0 = addP;
+
+        int n = k.bitLength();
+        int s = k.getLowestSetBit();
+
+        int i = n;
+        while (--i > s)
+        {
+            R0 = R0.twicePlus(k.testBit(i) ? addP : subP);
+        }
+
+        R0 = R0.timesPow2(s);
+
+        return R0;
+    }
+}