1 files changed, 75 insertions, 0 deletions
diff --git a/crypto/src/math/ec/multiplier/MixedNafR2LMultiplier.cs b/crypto/src/math/ec/multiplier/MixedNafR2LMultiplier.cs
new file mode 100644
index 000000000..a4c201832
--- /dev/null
+++ b/crypto/src/math/ec/multiplier/MixedNafR2LMultiplier.cs
@@ -0,0 +1,75 @@
+using System;
+
+namespace Org.BouncyCastle.Math.EC.Multiplier
+{
+    /**
+     * Class implementing the NAF (Non-Adjacent Form) multiplication algorithm (right-to-left) using
+     * mixed coordinates.
+     */
+    public class MixedNafR2LMultiplier 
+        : AbstractECMultiplier
+    {
+        protected readonly int additionCoord, doublingCoord;
+
+        /**
+         * By default, addition will be done in Jacobian coordinates, and doubling will be done in
+         * Modified Jacobian coordinates (independent of the original coordinate system of each point).
+         */
+        public MixedNafR2LMultiplier()
+            : this(ECCurve.COORD_JACOBIAN, ECCurve.COORD_JACOBIAN_MODIFIED)
+        {
+        }
+
+        public MixedNafR2LMultiplier(int additionCoord, int doublingCoord)
+        {
+            this.additionCoord = additionCoord;
+            this.doublingCoord = doublingCoord;
+        }
+
+        protected override ECPoint MultiplyPositive(ECPoint p, BigInteger k)
+        {
+            ECCurve curveOrig = p.Curve;
+
+            ECCurve curveAdd = ConfigureCurve(curveOrig, additionCoord);
+            ECCurve curveDouble = ConfigureCurve(curveOrig, doublingCoord);
+
+            int[] naf = WNafUtilities.GenerateCompactNaf(k);
+
+            ECPoint Ra = curveAdd.Infinity;
+            ECPoint Td = curveDouble.ImportPoint(p);
+
+            int zeroes = 0;
+            for (int i = 0; i < naf.Length; ++i)
+            {
+                int ni = naf[i];
+                int digit = ni >> 16;
+                zeroes += ni & 0xFFFF;
+
+                Td = Td.TimesPow2(zeroes);
+
+                ECPoint Tj = curveAdd.ImportPoint(Td);
+                if (digit < 0)
+                {
+                    Tj = Tj.Negate();
+                }
+
+                Ra = Ra.Add(Tj);
+
+                zeroes = 1;
+            }
+
+            return curveOrig.ImportPoint(Ra);
+        }
+
+        protected virtual ECCurve ConfigureCurve(ECCurve c, int coord)
+        {
+            if (c.CoordinateSystem == coord)
+                return c;
+
+            if (!c.SupportsCoordinateSystem(coord))
+                throw new ArgumentException("Coordinate system " + coord + " not supported by this curve", "coord");
+
+            return c.Configure().SetCoordinateSystem(coord).Create();
+        }
+    }
+}