CfbBlockCipher
using Org.BouncyCastle.Crypto.Parameters;
using System;
namespace Org.BouncyCastle.Crypto.Modes
{
public class CfbBlockCipher : IBlockCipherMode, IBlockCipher
{
private byte[] IV;
private byte[] cfbV;
private byte[] cfbOutV;
private bool encrypting;
private readonly int blockSize;
private readonly IBlockCipher cipher;
public IBlockCipher UnderlyingCipher => cipher;
public string AlgorithmName => cipher.AlgorithmName + "/CFB" + (blockSize * 8).ToString();
public bool IsPartialBlockOkay => true;
public CfbBlockCipher(IBlockCipher cipher, int bitBlockSize)
{
if (bitBlockSize < 8 || (bitBlockSize & 7) != 0)
throw new ArgumentException("CFB" + bitBlockSize.ToString() + " not supported", "bitBlockSize");
this.cipher = cipher;
blockSize = bitBlockSize / 8;
IV = new byte[cipher.GetBlockSize()];
cfbV = new byte[cipher.GetBlockSize()];
cfbOutV = new byte[cipher.GetBlockSize()];
}
public void Init(bool forEncryption, ICipherParameters parameters)
{
encrypting = forEncryption;
ParametersWithIV parametersWithIV = parameters as ParametersWithIV;
if (parametersWithIV != null) {
byte[] iV = parametersWithIV.GetIV();
int num = IV.Length - iV.Length;
Array.Copy(iV, 0, IV, num, iV.Length);
Array.Clear(IV, 0, num);
parameters = parametersWithIV.Parameters;
}
Reset();
if (parameters != null)
cipher.Init(true, parameters);
}
public int GetBlockSize()
{
return blockSize;
}
public int ProcessBlock(byte[] input, int inOff, byte[] output, int outOff)
{
if (!encrypting)
return DecryptBlock(input.AsSpan(inOff), output.AsSpan(outOff));
return EncryptBlock(input.AsSpan(inOff), output.AsSpan(outOff));
}
public int ProcessBlock(ReadOnlySpan<byte> input, Span<byte> output)
{
if (!encrypting)
return DecryptBlock(input, output);
return EncryptBlock(input, output);
}
private int EncryptBlock(ReadOnlySpan<byte> input, Span<byte> output)
{
Check.DataLength(input, blockSize, "input buffer too short");
Check.OutputLength(output, blockSize, "output buffer too short");
cipher.ProcessBlock(cfbV, cfbOutV);
for (int i = 0; i < blockSize; i++) {
output[i] = (byte)(cfbOutV[i] ^ input[i]);
}
Array.Copy(cfbV, blockSize, cfbV, 0, cfbV.Length - blockSize);
output.Slice(0, blockSize).CopyTo(cfbV.AsSpan(cfbV.Length - blockSize));
return blockSize;
}
private int DecryptBlock(ReadOnlySpan<byte> input, Span<byte> output)
{
Check.DataLength(input, blockSize, "input buffer too short");
Check.OutputLength(output, blockSize, "output buffer too short");
cipher.ProcessBlock(cfbV, 0, cfbOutV, 0);
Array.Copy(cfbV, blockSize, cfbV, 0, cfbV.Length - blockSize);
input.Slice(0, blockSize).CopyTo(cfbV.AsSpan(cfbV.Length - blockSize));
for (int i = 0; i < blockSize; i++) {
output[i] = (byte)(cfbOutV[i] ^ input[i]);
}
return blockSize;
}
public void Reset()
{
Array.Copy(IV, 0, cfbV, 0, IV.Length);
}
}
}