139 lines
3.0 KiB
C#
139 lines
3.0 KiB
C#
using System;
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using Org.BouncyCastle.Crypto.Parameters;
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namespace Org.BouncyCastle.Crypto.Modes;
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public class GOfbBlockCipher : IBlockCipher
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{
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private const int C1 = 16843012;
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private const int C2 = 16843009;
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private byte[] IV;
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private byte[] ofbV;
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private byte[] ofbOutV;
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private readonly int blockSize;
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private readonly IBlockCipher cipher;
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private bool firstStep = true;
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private int N3;
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private int N4;
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public string AlgorithmName => cipher.AlgorithmName + "/GCTR";
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public bool IsPartialBlockOkay => true;
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public GOfbBlockCipher(IBlockCipher cipher)
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{
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this.cipher = cipher;
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blockSize = cipher.GetBlockSize();
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if (blockSize != 8)
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{
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throw new ArgumentException("GCTR only for 64 bit block ciphers");
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}
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IV = new byte[cipher.GetBlockSize()];
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ofbV = new byte[cipher.GetBlockSize()];
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ofbOutV = new byte[cipher.GetBlockSize()];
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}
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public IBlockCipher GetUnderlyingCipher()
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{
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return cipher;
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}
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public void Init(bool forEncryption, ICipherParameters parameters)
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{
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firstStep = true;
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N3 = 0;
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N4 = 0;
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if (parameters is ParametersWithIV)
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{
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ParametersWithIV parametersWithIV = (ParametersWithIV)parameters;
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byte[] iV = parametersWithIV.GetIV();
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if (iV.Length < IV.Length)
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{
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Array.Copy(iV, 0, IV, IV.Length - iV.Length, iV.Length);
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for (int i = 0; i < IV.Length - iV.Length; i++)
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{
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IV[i] = 0;
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}
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}
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else
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{
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Array.Copy(iV, 0, IV, 0, IV.Length);
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}
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parameters = parametersWithIV.Parameters;
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}
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Reset();
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if (parameters != null)
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{
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cipher.Init(forEncryption: true, parameters);
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}
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}
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public int GetBlockSize()
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{
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return blockSize;
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}
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public int ProcessBlock(byte[] input, int inOff, byte[] output, int outOff)
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{
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if (inOff + blockSize > input.Length)
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{
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throw new DataLengthException("input buffer too short");
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}
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if (outOff + blockSize > output.Length)
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{
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throw new DataLengthException("output buffer too short");
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}
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if (firstStep)
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{
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firstStep = false;
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cipher.ProcessBlock(ofbV, 0, ofbOutV, 0);
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N3 = bytesToint(ofbOutV, 0);
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N4 = bytesToint(ofbOutV, 4);
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}
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N3 += 16843009;
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N4 += 16843012;
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if (N4 < 16843012 && N4 > 0)
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{
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N4++;
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}
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intTobytes(N3, ofbV, 0);
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intTobytes(N4, ofbV, 4);
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cipher.ProcessBlock(ofbV, 0, ofbOutV, 0);
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for (int i = 0; i < blockSize; i++)
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{
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output[outOff + i] = (byte)(ofbOutV[i] ^ input[inOff + i]);
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}
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Array.Copy(ofbV, blockSize, ofbV, 0, ofbV.Length - blockSize);
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Array.Copy(ofbOutV, 0, ofbV, ofbV.Length - blockSize, blockSize);
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return blockSize;
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}
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public void Reset()
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{
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Array.Copy(IV, 0, ofbV, 0, IV.Length);
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cipher.Reset();
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}
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private int bytesToint(byte[] inBytes, int inOff)
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{
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return (int)((inBytes[inOff + 3] << 24) & 0xFF000000u) + ((inBytes[inOff + 2] << 16) & 0xFF0000) + ((inBytes[inOff + 1] << 8) & 0xFF00) + (inBytes[inOff] & 0xFF);
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}
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private void intTobytes(int num, byte[] outBytes, int outOff)
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{
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outBytes[outOff + 3] = (byte)(num >> 24);
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outBytes[outOff + 2] = (byte)(num >> 16);
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outBytes[outOff + 1] = (byte)(num >> 8);
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outBytes[outOff] = (byte)num;
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}
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}
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