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70 lines
1.8 KiB
70 lines
1.8 KiB
using System;
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using Org.BouncyCastle.Crypto.Utilities;
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using Org.BouncyCastle.Utilities;
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namespace Org.BouncyCastle.Crypto.Modes.Gcm
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{
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public class Tables4kGcmMultiplier
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: IGcmMultiplier
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{
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private byte[] H;
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private ulong[] T;
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public void Init(byte[] H)
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{
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if (T == null)
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{
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T = new ulong[512];
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}
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else if (Arrays.AreEqual(this.H, H))
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{
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return;
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}
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this.H = Arrays.Clone(H);
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// T[0] = 0
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// T[1] = H.p^7
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GcmUtilities.AsUlongs(this.H, T, 2);
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GcmUtilities.MultiplyP7(T, 2, T, 2);
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for (int n = 2; n < 256; n += 2)
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{
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// T[2.n] = T[n].p^-1
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GcmUtilities.DivideP(T, n, T, n << 1);
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// T[2.n + 1] = T[2.n] + T[1]
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GcmUtilities.Xor(T, n << 1, T, 2, T, (n + 1) << 1);
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}
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}
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public void MultiplyH(byte[] x)
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{
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//ulong[] z = new ulong[2];
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//GcmUtilities.Copy(T, x[15] << 1, z, 0);
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//for (int i = 14; i >= 0; --i)
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//{
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// GcmUtilities.MultiplyP8(z);
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// GcmUtilities.Xor(z, 0, T, x[i] << 1);
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//}
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//Pack.UInt64_To_BE(z, x, 0);
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int pos = x[15] << 1;
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ulong z0 = T[pos + 0], z1 = T[pos + 1];
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for (int i = 14; i >= 0; --i)
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{
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pos = x[i] << 1;
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ulong c = z1 << 56;
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z1 = T[pos + 1] ^ ((z1 >> 8) | (z0 << 56));
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z0 = T[pos + 0] ^ (z0 >> 8) ^ c ^ (c >> 1) ^ (c >> 2) ^ (c >> 7);
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}
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Pack.UInt64_To_BE(z0, x, 0);
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Pack.UInt64_To_BE(z1, x, 8);
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}
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}
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}
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