Class OpenPGPCFBBlockCipher

java.lang.Object
org.gudy.bouncycastle.crypto.modes.OpenPGPCFBBlockCipher
All Implemented Interfaces:
BlockCipher

public class OpenPGPCFBBlockCipher extends 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 accommodates the reset after (blockSize + 2) bytes have been read.

For further info see RFC 2440.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    private int
     
    private BlockCipher
     
    private int
     
    private boolean
     
    private byte[]
     
    private byte[]
     
    private byte[]
     
    private byte[]
     
  • Constructor Summary

    Constructors
    Constructor
    Description
    Basic constructor.
  • Method Summary

    Modifier and Type
    Method
    Description
    private int
    decryptBlock(byte[] in, int inOff, byte[] out, int outOff)
    Do the appropriate processing for CFB IV mode decryption.
    private int
    encryptBlock(byte[] in, int inOff, byte[] out, int outOff)
    Do the appropriate processing for CFB IV mode encryption.
    private byte
    encryptByte(byte data, int blockOff)
    Encrypt one byte of data according to CFB mode.
    return the algorithm name and mode.
    int
    return the block size we are operating at.
    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 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
  • Field Details

    • IV

      private byte[] IV
    • FR

      private byte[] FR
    • FRE

      private byte[] FRE
    • tmp

      private byte[] tmp
    • cipher

      private BlockCipher cipher
    • count

      private int count
    • blockSize

      private int blockSize
    • forEncryption

      private boolean forEncryption
  • Constructor Details

    • OpenPGPCFBBlockCipher

      public OpenPGPCFBBlockCipher(BlockCipher cipher)
      Basic constructor.
      Parameters:
      cipher - the block cipher to be used as the basis of the feedback mode.
  • Method Details

    • getUnderlyingCipher

      public BlockCipher getUnderlyingCipher()
      return the underlying block cipher that we are wrapping.
      Returns:
      the underlying block cipher that we are wrapping.
    • getAlgorithmName

      public 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, 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.
      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 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.
      param - the key and other data required by the cipher.
      Throws:
      IllegalArgumentException - if the params argument is inappropriate.
    • encryptByte

      private byte encryptByte(byte data, int blockOff)
      Encrypt one byte of data according to CFB mode.
      Parameters:
      data - the byte to encrypt
      where - am i in the current block, determines when to resync the block
    • encryptBlock

      private int encryptBlock(byte[] in, int inOff, byte[] out, int outOff) throws DataLengthException, IllegalStateException
      Do the appropriate processing for CFB IV mode encryption.
      Parameters:
      in - the array containing the data to be encrypted.
      inOff - offset into the in array the data starts at.
      out - the array the encrypted 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.
      IllegalStateException - if the cipher isn't initialised.
    • decryptBlock

      private int decryptBlock(byte[] in, int inOff, byte[] out, int outOff) throws DataLengthException, IllegalStateException
      Do the appropriate processing for CFB IV mode decryption.
      Parameters:
      in - the array containing the data to be decrypted.
      inOff - offset into the in array the data starts at.
      out - the array the encrypted 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.
      IllegalStateException - if the cipher isn't initialised.