context: #if !BESTHTTP_DISABLE_ALTERNATE_SSL && (!UNITY_WEBGL || UNITY_EDITOR)
  
  using System;
  using System.Diagnostics;
  
  using Org.BouncyCastle.Math.Raw;
  
  namespace Org.BouncyCastle.Math.EC.Custom.Sec
  {
      internal class SecT233Field
      {
          private const ulong M41 = ulong.MaxValue >> 23;
          private const ulong M59 = ulong.MaxValue >> 5;
  
          public static void Add(ulong[] x, ulong[] y, ulong[] z)
          {
              z[0] = x[0] ^ y[0];
              z[1] = x[1] ^ y[1];
              z[2] = x[2] ^ y[2];
              z[3] = x[3] ^ y[3];
          }
  
          public static void AddExt(ulong[] xx, ulong[] yy, ulong[] zz)
          {
              zz[0] = xx[0] ^ yy[0];
              zz[1] = xx[1] ^ yy[1];
              zz[2] = xx[2] ^ yy[2];
              zz[3] = xx[3] ^ yy[3];
              zz[4] = xx[4] ^ yy[4];
              zz[5] = xx[5] ^ yy[5];
              zz[6] = xx[6] ^ yy[6];
              zz[7] = xx[7] ^ yy[7];
          }
  
          public static void AddOne(ulong[] x, ulong[] z)
          {
              z[0] = x[0] ^ 1UL;
              z[1] = x[1];
              z[2] = x[2];
              z[3] = x[3];
          }
  
          public static ulong[] FromBigInteger(BigInteger x)
          {
              ulong[] z = Nat256.FromBigInteger64(x);
              Reduce23(z, 0);
              return z;
          }
  
          public static void Multiply(ulong[] x, ulong[] y, ulong[] z)
          {
              ulong[] tt = Nat256.CreateExt64();
              ImplMultiply(x, y, tt);
              Reduce(tt, z);
          }
  
          public static void MultiplyAddToExt(ulong[] x, ulong[] y, ulong[] zz)
          {
              ulong[] tt = Nat256.CreateExt64();
              ImplMultiply(x, y, tt);
              AddExt(zz, tt, zz);
          }
  
          public static void Reduce(ulong[] xx, ulong[] z)
          {
              ulong x0 = xx[0], x1 = xx[1], x2 = xx[2], x3 = xx[3];
              ulong x4 = xx[4], x5 = xx[5], x6 = xx[6], x7 = xx[7];
  
              x3 ^= (x7 << 23);
              x4 ^= (x7 >> 41) ^ (x7 << 33);
              x5 ^= (x7 >> 31);
  
              x2 ^= (x6 << 23);
              x3 ^= (x6 >> 41) ^ (x6 << 33);
              x4 ^= (x6 >> 31);
  
              x1 ^= (x5 << 23);
              x2 ^= (x5 >> 41) ^ (x5 << 33);
              x3 ^= (x5 >> 31);
  
              x0 ^= (x4 << 23);
              x1 ^= (x4 >> 41) ^ (x4 << 33);
              x2 ^= (x4 >> 31);
  
              ulong t = x3 >> 41;
              z[0]    = x0 ^ t;
              z[1]    = x1 ^ (t << 10);
              z[2]    = x2;
              z[3]    = x3 & M41;
          }
  
          public static void Reduce23(ulong[] z, int zOff)
          {
              ulong z3     = z[zOff + 3], t = z3 >> 41;
              z[zOff    ] ^= t;
              z[zOff + 1] ^= (t << 10);
              z[zOff + 3]  = z3 & M41;
          }
  
          public static void Square(ulong[] x, ulong[] z)
          {
              ulong[] tt = Nat256.CreateExt64();
              ImplSquare(x, tt);
              Reduce(tt, z);
          }
  
          public static void SquareAddToExt(ulong[] x, ulong[] zz)
          {
              ulong[] tt = Nat256.CreateExt64();
              ImplSquare(x, tt);
              AddExt(zz, tt, zz);
          }
  
          public static void SquareN(ulong[] x, int n, ulong[] z)
          {
              Debug.Assert(n > 0);
  
              ulong[] tt = Nat256.CreateExt64();
              ImplSquare(x, tt);
              Reduce(tt, z);
  
              while (--n > 0)
              {
                  ImplSquare(z, tt);
                  Reduce(tt, z);
              }
          }
  
          protected static void ImplCompactExt(ulong[] zz)
          {
              ulong z0 = zz[0], z1 = zz[1], z2 = zz[2], z3 = zz[3], z4 = zz[4], z5 = zz[5], z6 = zz[6], z7 = zz[7];
              zz[0] =  z0         ^ (z1 << 59);
              zz[1] = (z1 >>  5) ^ (z2 << 54);
              zz[2] = (z2 >> 10) ^ (z3 << 49);
              zz[3] = (z3 >> 15) ^ (z4 << 44);
              zz[4] = (z4 >> 20) ^ (z5 << 39);
              zz[5] = (z5 >> 25) ^ (z6 << 34);
              zz[6] = (z6 >> 30) ^ (z7 << 29);
              zz[7] = (z7 >> 35);
          }
  
          protected static void ImplExpand(ulong[] x, ulong[] z)
          {
              ulong x0 = x[0], x1 = x[1], x2 = x[2], x3 = x[3];
              z[0] = x0 & M59;
              z[1] = ((x0 >> 59) ^ (x1 <<  5)) & M59;
              z[2] = ((x1 >> 54) ^ (x2 << 10)) & M59;
              z[3] = ((x2 >> 49) ^ (x3 << 15));
          }
  
          protected static void ImplMultiply(ulong[] x, ulong[] y, ulong[] zz)
          {
              /*
               * "Two-level seven-way recursion" as described in "Batch binary Edwards", Daniel J. Bernstein.
               */
  
              ulong[] f = new ulong[4], g = new ulong[4];
              ImplExpand(x, f);
              ImplExpand(y, g);
  
              ImplMulwAcc(f[0], g[0], zz, 0);
              ImplMulwAcc(f[1], g[1], zz, 1);
              ImplMulwAcc(f[2], g[2], zz, 2);
              ImplMulwAcc(f[3], g[3], zz, 3);
  
              // U *= (1 - t^n)
              for (int i = 5; i > 0; --i)
              {
                  zz[i] ^= zz[i - 1];
              }
  
              ImplMulwAcc(f[0] ^ f[1], g[0] ^ g[1], zz, 1);
              ImplMulwAcc(f[2] ^ f[3], g[2] ^ g[3], zz, 3);
  
              // V *= (1 - t^2n)
              for (int i = 7; i > 1; --i)
              {
                  zz[i] ^= zz[i - 2];
              }
  
              // Double-length recursion
              {
                  ulong c0 = f[0] ^ f[2], c1 = f[1] ^ f[3];
                  ulong d0 = g[0] ^ g[2], d1 = g[1] ^ g[3];
                  ImplMulwAcc(c0 ^ c1, d0 ^ d1, zz, 3);
                  ulong[] t = new ulong[3];
                  ImplMulwAcc(c0, d0, t, 0);
                  ImplMulwAcc(c1, d1, t, 1);
                  ulong t0 = t[0], t1 = t[1], t2 = t[2];
                  zz[2] ^= t0;
                  zz[3] ^= t0 ^ t1;
                  zz[4] ^= t2 ^ t1;
                  zz[5] ^= t2;
              }
  
              ImplCompactExt(zz);
          }
  
          protected static void ImplMulwAcc(ulong x, ulong y, ulong[] z, int zOff)
          {
              Debug.Assert(x >> 59 == 0);
              Debug.Assert(y >> 59 == 0);
  
              ulong[] u = new ulong[8];
      //      u[0] = 0;
              u[1] = y;
              u[2] = u[1] << 1;
              u[3] = u[2] ^  y;
              u[4] = u[2] << 1;
              u[5] = u[4] ^  y;
              u[6] = u[3] << 1;
              u[7] = u[6] ^  y;
  
              uint j = (uint)x;
              ulong g, h = 0, l = u[j & 7]
                                ^ (u[(j >> 3) & 7] << 3);
              int k = 54;
              do
              {
                  j = (uint)(x >> k);
                  g  = u[j & 7]
  
gt:                    ^ u[(j >> 3) & 7] << 3;