94 lines
2.0 KiB
C#
94 lines
2.0 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 OfbBlockCipher : IBlockCipher
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{
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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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public string AlgorithmName => cipher.AlgorithmName + "/OFB" + blockSize * 8;
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public bool IsPartialBlockOkay => true;
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public OfbBlockCipher(IBlockCipher cipher, int blockSize)
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{
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this.cipher = cipher;
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this.blockSize = blockSize / 8;
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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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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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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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}
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