up

2020-07-09 08:50:24 +08:00
parent 13d25f4707
commit c523462b82
1818 changed files with 174940 additions and 582 deletions
--- a/Assets/BestHTTP/SecureProtocol/math/ec/multiplier/WNafL2RMultiplier.cs
+++ b/Assets/BestHTTP/SecureProtocol/math/ec/multiplier/WNafL2RMultiplier.cs
@@ -0,0 +1,102 @@
+#if !BESTHTTP_DISABLE_ALTERNATE_SSL && (!UNITY_WEBGL || UNITY_EDITOR)
+
+using System;
+
+namespace Org.BouncyCastle.Math.EC.Multiplier
+{
+    /**
+    * Class implementing the WNAF (Window Non-Adjacent Form) multiplication
+    * algorithm.
+    */
+    public class WNafL2RMultiplier
+        : AbstractECMultiplier
+    {
+        /**
+         * Multiplies <code>this</code> by an integer <code>k</code> using the
+         * Window NAF method.
+         * @param k The integer by which <code>this</code> is multiplied.
+         * @return A new <code>ECPoint</code> which equals <code>this</code>
+         * multiplied by <code>k</code>.
+         */
+        protected override ECPoint MultiplyPositive(ECPoint p, BigInteger k)
+        {
+            // Clamp the window width in the range [2, 16]
+            int width = System.Math.Max(2, System.Math.Min(16, GetWindowSize(k.BitLength)));
+
+            WNafPreCompInfo wnafPreCompInfo = WNafUtilities.Precompute(p, width, true);
+            ECPoint[] preComp = wnafPreCompInfo.PreComp;
+            ECPoint[] preCompNeg = wnafPreCompInfo.PreCompNeg;
+
+            int[] wnaf = WNafUtilities.GenerateCompactWindowNaf(width, k);
+
+            ECPoint R = p.Curve.Infinity;
+
+            int i = wnaf.Length;
+
+            /*
+             * NOTE: We try to optimize the first window using the precomputed points to substitute an
+             * addition for 2 or more doublings.
+             */
+            if (i > 1)
+            {
+                int wi = wnaf[--i];
+                int digit = wi >> 16, zeroes = wi & 0xFFFF;
+
+                int n = System.Math.Abs(digit);
+                ECPoint[] table = digit < 0 ? preCompNeg : preComp;
+
+                // Optimization can only be used for values in the lower half of the table
+                if ((n << 2) < (1 << width))
+                {
+                    int highest = LongArray.BitLengths[n];
+
+                    // TODO Get addition/doubling cost ratio from curve and compare to 'scale' to see if worth substituting?
+                    int scale = width - highest;
+                    int lowBits = n ^ (1 << (highest - 1));
+
+                    int i1 = ((1 << (width - 1)) - 1);
+                    int i2 = (lowBits << scale) + 1;
+                    R = table[i1 >> 1].Add(table[i2 >> 1]);
+
+                    zeroes -= scale;
+
+                    //Console.WriteLine("Optimized: 2^" + scale + " * " + n + " = " + i1 + " + " + i2);
+                }
+                else
+                {
+                    R = table[n >> 1];
+                }
+
+                R = R.TimesPow2(zeroes);
+            }
+
+            while (i > 0)
+            {
+                int wi = wnaf[--i];
+                int digit = wi >> 16, zeroes = wi & 0xFFFF;
+
+                int n = System.Math.Abs(digit);
+                ECPoint[] table = digit < 0 ? preCompNeg : preComp;
+                ECPoint r = table[n >> 1];
+
+                R = R.TwicePlus(r);
+                R = R.TimesPow2(zeroes);
+            }
+
+            return R;
+        }
+
+        /**
+         * Determine window width to use for a scalar multiplication of the given size.
+         * 
+         * @param bits the bit-length of the scalar to multiply by
+         * @return the window size to use
+         */
+        protected virtual int GetWindowSize(int bits)
+        {
+            return WNafUtilities.GetWindowSize(bits);
+        }
+    }
+}
+
+#endif