Initial Commit

iTechSharp/srcbc/math/ec/multiplier/FpNafMultiplier.cs

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+namespace Org.BouncyCastle.Math.EC.Multiplier
+{
+	/**
+	* Class implementing the NAF (Non-Adjacent Form) multiplication algorithm.
+	*/
+	internal class FpNafMultiplier
+		: ECMultiplier
+	{
+		/**
+		* D.3.2 pg 101
+		* @see org.bouncycastle.math.ec.multiplier.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.Three);
+
+			ECPoint neg = p.Negate();
+			ECPoint R = p;
+
+			for (int i = h.BitLength - 2; i > 0; --i)
+			{             
+				R = R.Twice();
+
+				bool hBit = h.TestBit(i);
+				bool eBit = e.TestBit(i);
+
+				if (hBit != eBit)
+				{
+					R = R.Add(hBit ? p : neg);
+				}
+			}
+
+			return R;
+		}
+	}
+}