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using System;
using Org.BouncyCastle.Crypto.Utilities;
using Org.BouncyCastle.Utilities;
namespace Org.BouncyCastle.Crypto.Modes.Gcm
{
public class Tables8kGcmMultiplier
: IGcmMultiplier
{
private byte[] H;
private ulong[][] T;
public void Init(byte[] H)
{
if (T == null)
{
T = new ulong[2][];
}
else if (Arrays.AreEqual(this.H, H))
{
return;
}
this.H = Arrays.Clone(H);
for (int i = 0; i < 2; ++i)
{
ulong[] t = T[i] = new ulong[512];
// t[0] = 0
if (i == 0)
{
// t[1] = H.p^7
GcmUtilities.AsUlongs(this.H, t, 2);
GcmUtilities.MultiplyP7(t, 2, t, 2);
}
else
{
// t[1] = T[i-1][1].p^8
GcmUtilities.MultiplyP8(T[i - 1], 2, t, 2);
}
for (int n = 2; n < 256; n += 2)
{
// t[2.n] = t[n].p^-1
GcmUtilities.DivideP(t, n, t, n << 1);
// t[2.n + 1] = t[2.n] + t[1]
GcmUtilities.Xor(t, n << 1, t, 2, t, (n + 1) << 1);
}
}
}
public void MultiplyH(byte[] x)
{
ulong[] T0 = T[0], T1 = T[1];
//ulong[] z = new ulong[2];
//for (int i = 14; i >= 0; i -= 2)
//{
// GcmUtilities.MultiplyP16(z);
// GcmUtilities.Xor(z, 0, T0, x[i] << 1);
// GcmUtilities.Xor(z, 0, T1, x[i + 1] << 1);
//}
//Pack.UInt64_To_BE(z, x, 0);
int vPos = x[15] << 1;
int uPos = x[14] << 1;
ulong z1 = T0[uPos + 1] ^ T1[vPos + 1];
ulong z0 = T0[uPos] ^ T1[vPos];
for (int i = 12; i >= 0; i -= 2)
{
vPos = x[i + 1] << 1;
uPos = x[i] << 1;
ulong c = z1 << 48;
z1 = T0[uPos + 1] ^ T1[vPos + 1] ^ ((z1 >> 16) | (z0 << 48));
z0 = T0[uPos] ^ T1[vPos] ^ (z0 >> 16) ^ c ^ (c >> 1) ^ (c >> 2) ^ (c >> 7);
}
Pack.UInt64_To_BE(z0, x, 0);
Pack.UInt64_To_BE(z1, x, 8);
}
}
}
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