1 files changed, 29 insertions, 0 deletions
diff --git a/crypto/src/math/ec/multiplier/ZSignedDigitL2RMultiplier.cs b/crypto/src/math/ec/multiplier/ZSignedDigitL2RMultiplier.cs
new file mode 100644
index 000000000..554ac61b3
--- /dev/null
+++ b/crypto/src/math/ec/multiplier/ZSignedDigitL2RMultiplier.cs
@@ -0,0 +1,29 @@
+namespace Org.BouncyCastle.Math.EC.Multiplier
+{
+    public class ZSignedDigitL2RMultiplier 
+        : AbstractECMultiplier
+    {
+        /**
+         * 'Zeroless' Signed Digit Left-to-Right.
+         */
+        protected override 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;
+        }
+    }
+}