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using System;
using System.Diagnostics;
using Org.BouncyCastle.Math.Raw;
namespace Org.BouncyCastle.Math.EC.Custom.Sec
{
internal class SecP128R1Field
{
// 2^128 - 2^97 - 1
internal static readonly uint[] P = new uint[] { 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFD };
internal static readonly uint[] PExt = new uint[] { 0x00000001, 0x00000000, 0x00000000, 0x00000004, 0xFFFFFFFE,
0xFFFFFFFF, 0x00000003, 0xFFFFFFFC };
private static readonly uint[] PExtInv = new uint[]{ 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFB,
0x00000001, 0x00000000, 0xFFFFFFFC, 0x00000003 };
private const uint P3 = 0xFFFFFFFD;
private const uint PExt7 = 0xFFFFFFFC;
public static void Add(uint[] x, uint[] y, uint[] z)
{
uint c = Nat128.Add(x, y, z);
if (c != 0 || (z[3] >= P3 && Nat128.Gte(z, P)))
{
AddPInvTo(z);
}
}
public static void AddExt(uint[] xx, uint[] yy, uint[] zz)
{
uint c = Nat256.Add(xx, yy, zz);
if (c != 0 || (zz[7] >= PExt7 && Nat256.Gte(zz, PExt)))
{
Nat.AddTo(PExtInv.Length, PExtInv, zz);
}
}
public static void AddOne(uint[] x, uint[] z)
{
uint c = Nat.Inc(4, x, z);
if (c != 0 || (z[3] >= P3 && Nat128.Gte(z, P)))
{
AddPInvTo(z);
}
}
public static uint[] FromBigInteger(BigInteger x)
{
uint[] z = Nat128.FromBigInteger(x);
if (z[3] >= P3 && Nat128.Gte(z, P))
{
Nat128.SubFrom(P, z);
}
return z;
}
public static void Half(uint[] x, uint[] z)
{
if ((x[0] & 1) == 0)
{
Nat.ShiftDownBit(4, x, 0, z);
}
else
{
uint c = Nat128.Add(x, P, z);
Nat.ShiftDownBit(4, z, c);
}
}
public static void Multiply(uint[] x, uint[] y, uint[] z)
{
uint[] tt = Nat128.CreateExt();
Nat128.Mul(x, y, tt);
Reduce(tt, z);
}
public static void MultiplyAddToExt(uint[] x, uint[] y, uint[] zz)
{
uint c = Nat128.MulAddTo(x, y, zz);
if (c != 0 || (zz[7] >= PExt7 && Nat256.Gte(zz, PExt)))
{
Nat.AddTo(PExtInv.Length, PExtInv, zz);
}
}
public static void Negate(uint[] x, uint[] z)
{
if (Nat128.IsZero(x))
{
Nat128.Zero(z);
}
else
{
Nat128.Sub(P, x, z);
}
}
public static void Reduce(uint[] xx, uint[] 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; x6 += (x7 << 1);
x2 += x6; x5 += (x6 << 1);
x1 += x5; x4 += (x5 << 1);
x0 += x4; x3 += (x4 << 1);
z[0] = (uint)x0; x1 += (x0 >> 32);
z[1] = (uint)x1; x2 += (x1 >> 32);
z[2] = (uint)x2; x3 += (x2 >> 32);
z[3] = (uint)x3;
Reduce32((uint)(x3 >> 32), z);
}
public static void Reduce32(uint x, uint[] z)
{
while (x != 0)
{
ulong c, x4 = x;
c = (ulong)z[0] + x4;
z[0] = (uint)c; c >>= 32;
if (c != 0)
{
c += (ulong)z[1];
z[1] = (uint)c; c >>= 32;
c += (ulong)z[2];
z[2] = (uint)c; c >>= 32;
}
c += (ulong)z[3] + (x4 << 1);
z[3] = (uint)c; c >>= 32;
Debug.Assert(c >= 0 && c <= 2);
x = (uint)c;
}
}
public static void Square(uint[] x, uint[] z)
{
uint[] tt = Nat128.CreateExt();
Nat128.Square(x, tt);
Reduce(tt, z);
}
public static void SquareN(uint[] x, int n, uint[] z)
{
Debug.Assert(n > 0);
uint[] tt = Nat128.CreateExt();
Nat128.Square(x, tt);
Reduce(tt, z);
while (--n > 0)
{
Nat128.Square(z, tt);
Reduce(tt, z);
}
}
public static void Subtract(uint[] x, uint[] y, uint[] z)
{
int c = Nat128.Sub(x, y, z);
if (c != 0)
{
SubPInvFrom(z);
}
}
public static void SubtractExt(uint[] xx, uint[] yy, uint[] zz)
{
int c = Nat.Sub(10, xx, yy, zz);
if (c != 0)
{
Nat.SubFrom(PExtInv.Length, PExtInv, zz);
}
}
public static void Twice(uint[] x, uint[] z)
{
uint c = Nat.ShiftUpBit(4, x, 0, z);
if (c != 0 || (z[3] >= P3 && Nat128.Gte(z, P)))
{
AddPInvTo(z);
}
}
private static void AddPInvTo(uint[] z)
{
long c = (long)z[0] + 1;
z[0] = (uint)c; c >>= 32;
if (c != 0)
{
c += (long)z[1];
z[1] = (uint)c; c >>= 32;
c += (long)z[2];
z[2] = (uint)c; c >>= 32;
}
c += (long)z[3] + 2;
z[3] = (uint)c;
}
private static void SubPInvFrom(uint[] z)
{
long c = (long)z[0] - 1;
z[0] = (uint)c; c >>= 32;
if (c != 0)
{
c += (long)z[1];
z[1] = (uint)c; c >>= 32;
c += (long)z[2];
z[2] = (uint)c; c >>= 32;
}
c += (long)z[3] - 2;
z[3] = (uint)c;
}
}
}
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