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- // original: https://github.com/bcgit/bc-csharp/blob/master/crypto/src/crypto/modes/CfbBlockCipher.cs
- // changes: 5th parameter for ProcessBlock, to process without change internal state
-
-
- using Org.BouncyCastle.Crypto.Parameters;
- using System;
-
- namespace Org.BouncyCastle.Crypto.Modes
- {
- /**
- * implements a Cipher-FeedBack (CFB) mode on top of a simple cipher.
- */
- public class ExtendedCfbBlockCipher
- : IBlockCipher
- {
- private readonly byte[] IV;
- private readonly byte[] cfbV;
- private readonly byte[] cfbOutV;
- private bool encrypting;
-
- private readonly int blockSize;
- private readonly IBlockCipher cipher;
-
- /**
- * Basic constructor.
- *
- * @param cipher the block cipher to be used as the basis of the
- * feedback mode.
- * @param blockSize the block size in bits (note: a multiple of 8)
- */
- public ExtendedCfbBlockCipher(
- IBlockCipher cipher,
- int bitBlockSize)
- {
- this.cipher = cipher;
- blockSize = bitBlockSize / 8;
- IV = new byte[cipher.GetBlockSize()];
- cfbV = new byte[cipher.GetBlockSize()];
- cfbOutV = new byte[cipher.GetBlockSize()];
- }
- /**
- * return the underlying block cipher that we are wrapping.
- *
- * @return the underlying block cipher that we are wrapping.
- */
- public IBlockCipher GetUnderlyingCipher()
- {
- return cipher;
- }
- /**
- * Initialise the cipher and, possibly, the initialisation vector (IV).
- * If an IV isn't passed as part of the parameter, the IV will be all zeros.
- * An IV which is too short is handled in FIPS compliant fashion.
- *
- * @param forEncryption if true the cipher is initialised for
- * encryption, if false for decryption.
- * @param param the key and other data required by the cipher.
- * @exception ArgumentException if the parameters argument is
- * inappropriate.
- */
- public void Init(
- bool forEncryption,
- ICipherParameters parameters)
- {
- encrypting = forEncryption;
- if (parameters is ParametersWithIV ivParam)
- {
- byte[] iv = ivParam.GetIV();
- int diff = IV.Length - iv.Length;
- Array.Copy(iv, 0, IV, diff, iv.Length);
- Array.Clear(IV, 0, diff);
-
- parameters = ivParam.Parameters;
- }
- Reset();
-
- // if it's null, key is to be reused.
- if (parameters != null)
- {
- cipher.Init(true, parameters);
- }
- }
-
- /**
- * return the algorithm name and mode.
- *
- * @return the name of the underlying algorithm followed by "/CFB"
- * and the block size in bits.
- */
- public string AlgorithmName => cipher.AlgorithmName + "/CFB" + (blockSize * 8);
-
- public bool IsPartialBlockOkay => true;
-
- /**
- * return the block size we are operating at.
- *
- * @return the block size we are operating at (in bytes).
- */
- public int GetBlockSize()
- {
- return blockSize;
- }
-
- /**
- * Process one block of input from the array in and write it to
- * the out array.
- *
- * @param in the array containing the input data.
- * @param inOff offset into the in array the data starts at.
- * @param out the array the output data will be copied into.
- * @param outOff the offset into the out array the output will start at.
- * @param updateContext update internal state after process.
- * @exception DataLengthException if there isn't enough data in in, or
- * space in out.
- * @exception InvalidOperationException if the cipher isn't initialised.
- * @return the number of bytes processed and produced.
- */
- public int ProcessBlock(
- byte[] input,
- int inOff,
- byte[] output,
- int outOff,
- bool updateContext)
- {
- return (encrypting)
- ? EncryptBlock(input, inOff, output, outOff, updateContext)
- : DecryptBlock(input, inOff, output, outOff, updateContext);
- }
-
- /**
- * Do the appropriate processing for CFB mode encryption.
- *
- * @param in the array containing the data to be encrypted.
- * @param inOff offset into the in array the data starts at.
- * @param out the array the encrypted data will be copied into.
- * @param outOff the offset into the out array the output will start at.
- * @exception DataLengthException if there isn't enough data in in, or
- * space in out.
- * @exception InvalidOperationException if the cipher isn't initialised.
- * @return the number of bytes processed and produced.
- */
- public int EncryptBlock(
- byte[] input,
- int inOff,
- byte[] outBytes,
- int outOff,
- bool updateContext = true)
- {
- if ((inOff + blockSize) > input.Length)
- {
- throw new DataLengthException("input buffer too short");
- }
- if ((outOff + blockSize) > outBytes.Length)
- {
- throw new DataLengthException("output buffer too short");
- }
- cipher.ProcessBlock(cfbV, 0, cfbOutV, 0);
- //
- // XOR the cfbV with the plaintext producing the ciphertext
- //
- for (int i = 0; i < blockSize; i++)
- {
- outBytes[outOff + i] = (byte)(cfbOutV[i] ^ input[inOff + i]);
- }
- if (updateContext)
- {
- //
- // change over the input block.
- //
- Array.Copy(cfbV, blockSize, cfbV, 0, cfbV.Length - blockSize);
- Array.Copy(outBytes, outOff, cfbV, cfbV.Length - blockSize, blockSize);
- }
- return blockSize;
- }
- /**
- * Do the appropriate processing for CFB mode decryption.
- *
- * @param in the array containing the data to be decrypted.
- * @param inOff offset into the in array the data starts at.
- * @param out the array the encrypted data will be copied into.
- * @param outOff the offset into the out array the output will start at.
- * @exception DataLengthException if there isn't enough data in in, or
- * space in out.
- * @exception InvalidOperationException if the cipher isn't initialised.
- * @return the number of bytes processed and produced.
- */
- public int DecryptBlock(
- byte[] input,
- int inOff,
- byte[] outBytes,
- int outOff,
- bool updateContext = true)
- {
- if ((inOff + blockSize) > input.Length)
- {
- throw new DataLengthException("input buffer too short");
- }
- if ((outOff + blockSize) > outBytes.Length)
- {
- throw new DataLengthException("output buffer too short");
- }
- cipher.ProcessBlock(cfbV, 0, cfbOutV, 0);
- if (updateContext)
- {
- //
- // change over the input block.
- //
- Array.Copy(cfbV, blockSize, cfbV, 0, cfbV.Length - blockSize);
- Array.Copy(input, inOff, cfbV, cfbV.Length - blockSize, blockSize);
- }
- //
- // XOR the cfbV with the ciphertext producing the plaintext
- //
- for (int i = 0; i < blockSize; i++)
- {
- outBytes[outOff + i] = (byte)(cfbOutV[i] ^ input[inOff + i]);
- }
- return blockSize;
- }
- /**
- * reset the chaining vector back to the IV and reset the underlying
- * cipher.
- */
- public void Reset()
- {
- Array.Copy(IV, 0, cfbV, 0, IV.Length);
- cipher.Reset();
- }
-
- public int ProcessBlock(byte[] inBuf, int inOff, byte[] outBuf, int outOff)
- {
- return ProcessBlock(inBuf, inOff, outBuf, outOff, true);
- }
- }
- }
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