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using System;
using System.Diagnostics;
#if NETSTANDARD1_0_OR_GREATER || NETCOREAPP1_0_OR_GREATER
using System.Runtime.CompilerServices;
#endif
#if NETCOREAPP3_0_OR_GREATER
using System.Runtime.Intrinsics;
using System.Runtime.Intrinsics.X86;
#endif
using Org.BouncyCastle.Crypto.Utilities;
using Org.BouncyCastle.Math.Raw;
using Org.BouncyCastle.Utilities;
namespace Org.BouncyCastle.Crypto.Modes.Gcm
{
internal static class GcmUtilities
{
internal struct FieldElement
{
internal ulong n0, n1;
}
private const uint E1 = 0xe1000000;
private const ulong E1UL = (ulong)E1 << 32;
internal static void One(out FieldElement x)
{
x.n0 = 1UL << 63;
x.n1 = 0UL;
}
#if NETSTANDARD1_0_OR_GREATER || NETCOREAPP1_0_OR_GREATER
[MethodImpl(MethodImplOptions.AggressiveInlining)]
#endif
internal static void AsBytes(ulong x0, ulong x1, byte[] z)
{
Pack.UInt64_To_BE(x0, z, 0);
Pack.UInt64_To_BE(x1, z, 8);
}
#if NETSTANDARD1_0_OR_GREATER || NETCOREAPP1_0_OR_GREATER
[MethodImpl(MethodImplOptions.AggressiveInlining)]
#endif
internal static void AsBytes(ref FieldElement x, byte[] z)
{
AsBytes(x.n0, x.n1, z);
}
#if NETSTANDARD1_0_OR_GREATER || NETCOREAPP1_0_OR_GREATER
[MethodImpl(MethodImplOptions.AggressiveInlining)]
#endif
internal static void AsFieldElement(byte[] x, out FieldElement z)
{
z.n0 = Pack.BE_To_UInt64(x, 0);
z.n1 = Pack.BE_To_UInt64(x, 8);
}
internal static void DivideP(ref FieldElement x, out FieldElement z)
{
ulong x0 = x.n0, x1 = x.n1;
ulong m = (ulong)((long)x0 >> 63);
x0 ^= (m & E1UL);
z.n0 = (x0 << 1) | (x1 >> 63);
z.n1 = (x1 << 1) | (ulong)(-(long)m);
}
internal static void Multiply(byte[] x, byte[] y)
{
AsFieldElement(x, out FieldElement X);
AsFieldElement(y, out FieldElement Y);
Multiply(ref X, ref Y);
AsBytes(ref X, x);
}
internal static void Multiply(ref FieldElement x, ref FieldElement y)
{
ulong z0, z1, z2, z3;
#if NETCOREAPP3_0_OR_GREATER
if (Pclmulqdq.IsSupported)
{
var X = Vector128.Create(x.n1, x.n0);
var Y = Vector128.Create(y.n1, y.n0);
var Z0 = Pclmulqdq.CarrylessMultiply(X, Y, 0x00);
var Z1 = Sse2.Xor(
Pclmulqdq.CarrylessMultiply(X, Y, 0x01),
Pclmulqdq.CarrylessMultiply(X, Y, 0x10));
var Z2 = Pclmulqdq.CarrylessMultiply(X, Y, 0x11);
ulong t3 = Z0.GetElement(0);
ulong t2 = Z0.GetElement(1) ^ Z1.GetElement(0);
ulong t1 = Z2.GetElement(0) ^ Z1.GetElement(1);
ulong t0 = Z2.GetElement(1);
z0 = (t0 << 1) | (t1 >> 63);
z1 = (t1 << 1) | (t2 >> 63);
z2 = (t2 << 1) | (t3 >> 63);
z3 = (t3 << 1);
}
else
#endif
{
/*
* "Three-way recursion" as described in "Batch binary Edwards", Daniel J. Bernstein.
*
* Without access to the high part of a 64x64 product x * y, we use a bit reversal to calculate it:
* rev(x) * rev(y) == rev((x * y) << 1)
*/
ulong x0 = x.n0, x1 = x.n1;
ulong y0 = y.n0, y1 = y.n1;
ulong x0r = Longs.Reverse(x0), x1r = Longs.Reverse(x1);
ulong y0r = Longs.Reverse(y0), y1r = Longs.Reverse(y1);
ulong h0 = Longs.Reverse(ImplMul64(x0r, y0r));
ulong h1 = ImplMul64(x0, y0) << 1;
ulong h2 = Longs.Reverse(ImplMul64(x1r, y1r));
ulong h3 = ImplMul64(x1, y1) << 1;
ulong h4 = Longs.Reverse(ImplMul64(x0r ^ x1r, y0r ^ y1r));
ulong h5 = ImplMul64(x0 ^ x1, y0 ^ y1) << 1;
z0 = h0;
z1 = h1 ^ h0 ^ h2 ^ h4;
z2 = h2 ^ h1 ^ h3 ^ h5;
z3 = h3;
}
Debug.Assert(z3 << 63 == 0);
z1 ^= z3 ^ (z3 >> 1) ^ (z3 >> 2) ^ (z3 >> 7);
// z2 ^= (z3 << 63) ^ (z3 << 62) ^ (z3 << 57);
z2 ^= (z3 << 62) ^ (z3 << 57);
z0 ^= z2 ^ (z2 >> 1) ^ (z2 >> 2) ^ (z2 >> 7);
z1 ^= (z2 << 63) ^ (z2 << 62) ^ (z2 << 57);
x.n0 = z0;
x.n1 = z1;
}
internal static void MultiplyP7(ref FieldElement x)
{
ulong x0 = x.n0, x1 = x.n1;
ulong c = x1 << 57;
x.n0 = (x0 >> 7) ^ c ^ (c >> 1) ^ (c >> 2) ^ (c >> 7);
x.n1 = (x1 >> 7) | (x0 << 57);
}
internal static void MultiplyP8(ref FieldElement x)
{
ulong x0 = x.n0, x1 = x.n1;
ulong c = x1 << 56;
x.n0 = (x0 >> 8) ^ c ^ (c >> 1) ^ (c >> 2) ^ (c >> 7);
x.n1 = (x1 >> 8) | (x0 << 56);
}
internal static void MultiplyP8(ref FieldElement x, out FieldElement y)
{
ulong x0 = x.n0, x1 = x.n1;
ulong c = x1 << 56;
y.n0 = (x0 >> 8) ^ c ^ (c >> 1) ^ (c >> 2) ^ (c >> 7);
y.n1 = (x1 >> 8) | (x0 << 56);
}
internal static void MultiplyP16(ref FieldElement x)
{
ulong x0 = x.n0, x1 = x.n1;
ulong c = x1 << 48;
x.n0 = (x0 >> 16) ^ c ^ (c >> 1) ^ (c >> 2) ^ (c >> 7);
x.n1 = (x1 >> 16) | (x0 << 48);
}
internal static void Square(ref FieldElement x)
{
ulong z1 = Interleave.Expand64To128Rev(x.n0, out ulong z0);
ulong z3 = Interleave.Expand64To128Rev(x.n1, out ulong z2);
Debug.Assert(z3 << 63 == 0UL);
z1 ^= z3 ^ (z3 >> 1) ^ (z3 >> 2) ^ (z3 >> 7);
// z2 ^= (z3 << 63) ^ (z3 << 62) ^ (z3 << 57);
z2 ^= (z3 << 62) ^ (z3 << 57);
Debug.Assert(z2 << 63 == 0UL);
z0 ^= z2 ^ (z2 >> 1) ^ (z2 >> 2) ^ (z2 >> 7);
// z1 ^= (z2 << 63) ^ (z2 << 62) ^ (z2 << 57);
z1 ^= (z2 << 62) ^ (z2 << 57);
x.n0 = z0;
x.n1 = z1;
}
internal static void Xor(byte[] x, byte[] y)
{
int i = 0;
do
{
x[i] ^= y[i]; ++i;
x[i] ^= y[i]; ++i;
x[i] ^= y[i]; ++i;
x[i] ^= y[i]; ++i;
}
while (i < 16);
}
internal static void Xor(byte[] x, byte[] y, int yOff)
{
int i = 0;
do
{
x[i] ^= y[yOff + i]; ++i;
x[i] ^= y[yOff + i]; ++i;
x[i] ^= y[yOff + i]; ++i;
x[i] ^= y[yOff + i]; ++i;
}
while (i < 16);
}
internal static void Xor(byte[] x, byte[] y, int yOff, int yLen)
{
while (--yLen >= 0)
{
x[yLen] ^= y[yOff + yLen];
}
}
internal static void Xor(byte[] x, int xOff, byte[] y, int yOff, int len)
{
while (--len >= 0)
{
x[xOff + len] ^= y[yOff + len];
}
}
internal static void Xor(ref FieldElement x, ref FieldElement y)
{
x.n0 ^= y.n0;
x.n1 ^= y.n1;
}
internal static void Xor(ref FieldElement x, ref FieldElement y, out FieldElement z)
{
z.n0 = x.n0 ^ y.n0;
z.n1 = x.n1 ^ y.n1;
}
#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
internal static void Xor(Span<byte> x, ReadOnlySpan<byte> y)
{
int i = 0;
do
{
x[i] ^= y[i]; ++i;
x[i] ^= y[i]; ++i;
x[i] ^= y[i]; ++i;
x[i] ^= y[i]; ++i;
}
while (i < 16);
}
internal static void Xor(Span<byte> x, ReadOnlySpan<byte> y, int len)
{
for (int i = 0; i < len; ++i)
{
x[i] ^= y[i];
}
}
#endif
private static ulong ImplMul64(ulong x, ulong y)
{
ulong x0 = x & 0x1111111111111111UL;
ulong x1 = x & 0x2222222222222222UL;
ulong x2 = x & 0x4444444444444444UL;
ulong x3 = x & 0x8888888888888888UL;
ulong y0 = y & 0x1111111111111111UL;
ulong y1 = y & 0x2222222222222222UL;
ulong y2 = y & 0x4444444444444444UL;
ulong y3 = y & 0x8888888888888888UL;
ulong z0 = (x0 * y0) ^ (x1 * y3) ^ (x2 * y2) ^ (x3 * y1);
ulong z1 = (x0 * y1) ^ (x1 * y0) ^ (x2 * y3) ^ (x3 * y2);
ulong z2 = (x0 * y2) ^ (x1 * y1) ^ (x2 * y0) ^ (x3 * y3);
ulong z3 = (x0 * y3) ^ (x1 * y2) ^ (x2 * y1) ^ (x3 * y0);
z0 &= 0x1111111111111111UL;
z1 &= 0x2222222222222222UL;
z2 &= 0x4444444444444444UL;
z3 &= 0x8888888888888888UL;
return z0 | z1 | z2 | z3;
}
}
}
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