- Initial commit

Runtime/3rdParty/BouncyCastle/math/ec/multiplier/FixedPointCombMultiplier.cs

@@ -0,0 +1,69 @@
+#if !BESTHTTP_DISABLE_ALTERNATE_SSL && (!UNITY_WEBGL || UNITY_EDITOR)
+#pragma warning disable
+using System;
+
+using Best.HTTP.SecureProtocol.Org.BouncyCastle.Math.Raw;
+
+namespace Best.HTTP.SecureProtocol.Org.BouncyCastle.Math.EC.Multiplier
+{
+    public class FixedPointCombMultiplier
+        : AbstractECMultiplier
+    {
+        protected override ECPoint MultiplyPositive(ECPoint p, BigInteger k)
+        {
+            ECCurve c = p.Curve;
+            int size = FixedPointUtilities.GetCombSize(c);
+
+            if (k.BitLength > size)
+            {
+                /*
+                 * TODO The comb works best when the scalars are less than the (possibly unknown) order.
+                 * Still, if we want to handle larger scalars, we could allow customization of the comb
+                 * size, or alternatively we could deal with the 'extra' bits either by running the comb
+                 * multiple times as necessary, or by using an alternative multiplier as prelude.
+                 */
+                throw new InvalidOperationException("fixed-point comb doesn't support scalars larger than the curve order");
+            }
+
+            FixedPointPreCompInfo info = FixedPointUtilities.Precompute(p);
+            ECLookupTable lookupTable = info.LookupTable;
+            int width = info.Width;
+
+            int d = (size + width - 1) / width;
+            int fullComb = d * width;
+
+            ECPoint R = c.Infinity;
+
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER || UNITY_2021_2_OR_NEWER
+            int KLen = Nat.GetLengthForBits(fullComb);
+            Span<uint> K = KLen <= 32
+                ? stackalloc uint[KLen]
+                : new uint[KLen];
+            Nat.FromBigInteger(fullComb, k, K);
+#else
+            uint[] K = Nat.FromBigInteger(fullComb, k);
+#endif
+
+            for (int i = 1; i <= d; ++i)
+            {
+                uint secretIndex = 0;
+
+                for (int j = fullComb - i; j >= 0; j -= d)
+                {
+                    uint secretBit = K[j >> 5] >> (j & 0x1F);
+                    secretIndex ^= secretBit >> 1;
+                    secretIndex <<= 1;
+                    secretIndex ^= secretBit;
+                }
+
+                ECPoint add = lookupTable.Lookup((int)secretIndex);
+
+                R = R.TwicePlus(add);
+            }
+
+            return R.Add(info.Offset);
+        }
+    }
+}
+#pragma warning restore
+#endif