1 files changed, 39 insertions, 0 deletions
diff --git a/core/src/main/java/org/bouncycastle/math/ec/FpNafMultiplier.java b/core/src/main/java/org/bouncycastle/math/ec/FpNafMultiplier.java
new file mode 100644
index 00000000..35e601d5
--- /dev/null
+++ b/core/src/main/java/org/bouncycastle/math/ec/FpNafMultiplier.java
@@ -0,0 +1,39 @@
+package org.bouncycastle.math.ec;
+
+import java.math.BigInteger;
+
+/**
+ * Class implementing the NAF (Non-Adjacent Form) multiplication algorithm.
+ */
+class FpNafMultiplier implements ECMultiplier
+{
+    /**
+     * D.3.2 pg 101
+     * @see org.bouncycastle.math.ec.ECMultiplier#multiply(org.bouncycastle.math.ec.ECPoint, java.math.BigInteger)
+     */
+    public ECPoint multiply(ECPoint p, BigInteger k, PreCompInfo preCompInfo)
+    {
+        // TODO Probably should try to add this
+        // BigInteger e = k.mod(n); // n == order of p
+        BigInteger e = k;
+        BigInteger h = e.multiply(BigInteger.valueOf(3));
+
+        ECPoint neg = p.negate();
+        ECPoint R = p;
+
+        for (int i = h.bitLength() - 2; i > 0; --i)
+        {             
+            R = R.twice();
+
+            boolean hBit = h.testBit(i);
+            boolean eBit = e.testBit(i);
+
+            if (hBit != eBit)
+            {
+                R = R.add(hBit ? p : neg);
+            }
+        }
+
+        return R;
+    }
+}