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using System;
using System.Diagnostics;
namespace Org.BouncyCastle.Math.EC.Custom.Sec
{
internal class SecP256R1Field
{
// 2^256 - 2^224 + 2^192 + 2^96 - 1
internal static readonly uint[] P = new uint[]{ 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0x00000000, 0x00000000, 0x00000000,
0x00000001, 0xFFFFFFFF };
internal static readonly uint[] PExt = new uint[]{ 0x00000001, 0x00000000, 0x00000000, 0xFFFFFFFE, 0xFFFFFFFF,
0xFFFFFFFF, 0xFFFFFFFE, 0x00000001, 0xFFFFFFFE, 0x00000001, 0xFFFFFFFE, 0x00000001, 0x00000001, 0xFFFFFFFE,
0x00000002, 0xFFFFFFFE };
private static readonly uint[] _2P = new uint[]{ 0xFFFFFFFE, 0xFFFFFFFF, 0xFFFFFFFF, 0x00000001, 0x00000000, 0x00000000,
0x00000002, 0xFFFFFFFE, 0x00000001 };
private const uint P7 = 0xFFFFFFFF;
public static void Add(uint[] x, uint[] y, uint[] z)
{
uint c = Nat256.Add(x, y, z);
if (c != 0 || (z[7] == P7 && Nat256.Gte(z, P)))
{
Nat256.SubFrom(P, z);
}
}
public static void AddExt(uint[] xx, uint[] yy, uint[] zz)
{
uint c = Nat256.AddExt(xx, yy, zz);
if (c != 0 || Nat256.GteExt(zz, PExt))
{
Nat256.SubExt(zz, PExt, zz);
}
}
public static void AddOne(uint[] x, uint[] z)
{
Nat256.Copy(x, z);
uint c = Nat256.Inc(z, 0);
if (c != 0 || (z[7] == P7 && Nat256.Gte(z, P)))
{
Nat256.SubFrom(P, z);
}
}
public static uint[] FromBigInteger(BigInteger x)
{
uint[] z = Nat256.FromBigInteger(x);
if (z[7] == P7 && Nat256.Gte(z, P))
{
Nat256.SubFrom(P, z);
}
return z;
}
public static void Half(uint[] x, uint[] z)
{
if ((x[0] & 1) == 0)
{
Nat256.ShiftDownBit(x, 0, z);
}
else
{
uint c = Nat256.Add(x, P, z);
Nat256.ShiftDownBit(z, c, z);
}
}
public static void Multiply(uint[] x, uint[] y, uint[] z)
{
uint[] tt = Nat256.CreateExt();
Nat256.Mul(x, y, tt);
Reduce(tt, z);
}
public static void Negate(uint[] x, uint[] z)
{
if (Nat256.IsZero(x))
{
Nat256.Zero(z);
}
else
{
Nat256.Sub(P, x, z);
}
}
public static void Reduce(uint[] xx, uint[] z)
{
long xx08 = xx[8], xx09 = xx[9], xx10 = xx[10], xx11 = xx[11];
long xx12 = xx[12], xx13 = xx[13], xx14 = xx[14], xx15 = xx[15];
long t0 = xx08 + xx09;
long t1 = xx09 + xx10;
long t2 = xx10 + xx11;
long t3 = xx11 + xx12;
long t4 = xx12 + xx13;
long t5 = xx13 + xx14;
long t6 = xx14 + xx15;
long cc = 0;
cc += (long)xx[0] + t0 - t3 - t5;
z[0] = (uint)cc;
cc >>= 32;
cc += (long)xx[1] + t1 - t4 - t6;
z[1] = (uint)cc;
cc >>= 32;
cc += (long)xx[2] + t2 - t5 - xx15;
z[2] = (uint)cc;
cc >>= 32;
cc += (long)xx[3] + (t3 << 1) + xx13 - xx15 - t0;
z[3] = (uint)cc;
cc >>= 32;
cc += (long)xx[4] + (t4 << 1) + xx14 - t1;
z[4] = (uint)cc;
cc >>= 32;
cc += (long)xx[5] + (t5 << 1) + xx15 - t2;
z[5] = (uint)cc;
cc >>= 32;
cc += (long)xx[6] + (t6 << 1) + t5 - t0;
z[6] = (uint)cc;
cc >>= 32;
cc += (long)xx[7] + (xx15 << 1) + xx15 + xx08 - t2 - t4;
z[7] = (uint)cc;
cc >>= 32;
int c = (int)cc;
if (c >= 0)
{
Reduce32((uint)c, z);
}
else
{
while (c < -1)
{
c += (int)Nat256.AddTo(_2P, z) + 1;
}
while (c < 0)
{
c += (int)Nat256.AddTo(P, z);
}
}
}
public static void Reduce32(uint x, uint[] z)
{
long cc = 0;
if (x != 0)
{
long xx08 = x;
cc += (long)z[0] + xx08;
z[0] = (uint)cc;
cc >>= 32;
cc += (long)z[1];
z[1] = (uint)cc;
cc >>= 32;
cc += (long)z[2];
z[2] = (uint)cc;
cc >>= 32;
cc += (long)z[3] - xx08;
z[3] = (uint)cc;
cc >>= 32;
cc += (long)z[4];
z[4] = (uint)cc;
cc >>= 32;
cc += (long)z[5];
z[5] = (uint)cc;
cc >>= 32;
cc += (long)z[6] - xx08;
z[6] = (uint)cc;
cc >>= 32;
cc += (long)z[7] + xx08;
z[7] = (uint)cc;
cc >>= 32;
Debug.Assert(cc == 0 || cc == 1);
}
if (cc != 0 || (z[7] == P7 && Nat256.Gte(z, P)))
{
Nat256.SubFrom(P, z);
}
}
public static void Square(uint[] x, uint[] z)
{
uint[] tt = Nat256.CreateExt();
Nat256.Square(x, tt);
Reduce(tt, z);
}
public static void SquareN(uint[] x, int n, uint[] z)
{
Debug.Assert(n > 0);
uint[] tt = Nat256.CreateExt();
Nat256.Square(x, tt);
Reduce(tt, z);
while (--n > 0)
{
Nat256.Square(z, tt);
Reduce(tt, z);
}
}
public static void Subtract(uint[] x, uint[] y, uint[] z)
{
int c = Nat256.Sub(x, y, z);
if (c != 0)
{
Nat256.AddTo(P, z);
}
}
public static void SubtractExt(uint[] xx, uint[] yy, uint[] zz)
{
int c = Nat256.SubExt(xx, yy, zz);
if (c != 0)
{
Nat256.AddExt(zz, PExt, zz);
}
}
public static void Twice(uint[] x, uint[] z)
{
uint c = Nat256.ShiftUpBit(x, 0, z);
if (c != 0 || (z[7] == P7 && Nat256.Gte(z, P)))
{
Nat256.SubFrom(P, z);
}
}
}
}
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