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## org.bouncycastle.crypto.modes
Class OpenPGPCFBBlockCipher

    java.lang.Object
      org.bouncycastle.crypto.modes.OpenPGPCFBBlockCipher

All Implemented Interfaces:
  BlockCipher

public class OpenPGPCFBBlockCipher
extends java.lang.Object
implements BlockCipher

Implements OpenPGP's rather strange version of Cipher-FeedBack (CFB) mode on top of a simple cipher. This class assumes the IV has been prepended to the data stream already, and just accomodates the reset after (blockSize + 2) bytes have been read.

For further info see RFC 2440.

Constructor Summary
`OpenPGPCFBBlockCipher(BlockCipher cipher)` Basic constructor.

Method Summary
`java.lang.String` | `getAlgorithmName()` return the algorithm name and mode.
`int` | `getBlockSize()` return the block size we are operating at.
`BlockCipher` | `getUnderlyingCipher()` return the underlying block cipher that we are wrapping.
`void` | `init(boolean forEncryption, CipherParameters params)` Initialise the cipher and, possibly, the initialisation vector (IV).
`int` | `processBlock(byte[] in, int inOff, byte[] out, int outOff)` Process one block of input from the array in and write it to the out array.
`void` | `reset()` reset the chaining vector back to the IV and reset the underlying cipher.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### OpenPGPCFBBlockCipher

    public OpenPGPCFBBlockCipher(BlockCipher cipher)

  Basic constructor.

Parameters:
  `cipher` - the block cipher to be used as the basis of the feedback mode.

Method Detail

### getUnderlyingCipher

    public BlockCipher getUnderlyingCipher()

  return the underlying block cipher that we are wrapping.

  Returns:
    the underlying block cipher that we are wrapping.

### getAlgorithmName

    public java.lang.String getAlgorithmName()

  return the algorithm name and mode.

  Specified by:
    `getAlgorithmName` in interface `BlockCipher`
  Returns:
    the name of the underlying algorithm followed by "/PGPCFB" and the block size in bits.

### getBlockSize

    public int getBlockSize()

  return the block size we are operating at.

  Specified by:
    `getBlockSize` in interface `BlockCipher`
  Returns:
    the block size we are operating at (in bytes).

### processBlock

    public int processBlock(byte[] in,
                            int inOff,
                            byte[] out,
                            int outOff)
                     throws DataLengthException,
                            java.lang.IllegalStateException

  Process one block of input from the array in and write it to the out array.

  Specified by:
    `processBlock` in interface `BlockCipher`
  Parameters:
    `in` - the array containing the input data.
    `inOff` - offset into the in array the data starts at.
    `out` - the array the output data will be copied into.
    `outOff` - the offset into the out array the output will start at.
  Returns:
    the number of bytes processed and produced.
  Throws:
    `DataLengthException` - if there isn't enough data in in, or space in out.
    `java.lang.IllegalStateException` - if the cipher isn't initialised.

### reset

    public void reset()

  reset the chaining vector back to the IV and reset the underlying cipher.

  Specified by:
    `reset` in interface `BlockCipher`

### init

    public void init(boolean forEncryption,
                     CipherParameters params)
              throws java.lang.IllegalArgumentException

  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.

  Specified by:
    `init` in interface `BlockCipher`
  Parameters:
    `forEncryption` - if true the cipher is initialised for encryption, if false for decryption.
    `params` - the key and other data required by the cipher.
  Throws:
    `java.lang.IllegalArgumentException` - if the params argument is inappropriate.

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