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gnu.javax.crypto.mode
Class CBC  view CBC download CBC.java

java.lang.Object
  extended bygnu.javax.crypto.mode.BaseMode
      extended bygnu.javax.crypto.mode.CBC
All Implemented Interfaces:
java.lang.Cloneable, gnu.javax.crypto.cipher.IBlockCipher, IMode

public class CBC
extends BaseMode
implements java.lang.Cloneable

The Cipher Block Chaining mode. This mode introduces feedback into the cipher by XORing the previous ciphertext block with the plaintext block before encipherment. That is, encrypting looks like this:

Ci = EK(Pi ^ Ci-1

Similarly, decrypting is:

Pi = Ci-1 ^ DK(Ci)


Field Summary
private  byte[] lastBlock
          The last (de|en)crypted block
private  byte[] scratch
          An intermediate buffer.
 
Fields inherited from class gnu.javax.crypto.mode.BaseMode
cipher, cipherBlockSize, iv, lock, modeBlockSize, name, state
 
Fields inherited from interface gnu.javax.crypto.mode.IMode
DECRYPTION, ENCRYPTION, IV, MODE_BLOCK_SIZE, STATE
 
Fields inherited from interface gnu.javax.crypto.cipher.IBlockCipher
CIPHER_BLOCK_SIZE, KEY_MATERIAL
 
Constructor Summary
private CBC(CBC that)
          Our constructor for cloning.
(package private) CBC(gnu.javax.crypto.cipher.IBlockCipher underlyingCipher, int cipherBlockSize)
          Package-private constructor for the factory class.
 
Method Summary
 java.lang.Object clone()
          Returns a clone of this instance.
 void decryptBlock(byte[] in, int i, byte[] out, int o)
          Decrypts exactly one block of ciphertext.
 void encryptBlock(byte[] in, int i, byte[] out, int o)
          Encrypts exactly one block of plaintext.
 void setup()
          The initialisation phase of the concrete mode implementation.
 void teardown()
          The termination phase of the concrete mode implementation.
 
Methods inherited from class gnu.javax.crypto.mode.BaseMode
blockSizes, currentBlockSize, defaultBlockSize, defaultKeySize, init, keySizes, name, reset, selfTest, update
 
Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

lastBlock

private byte[] lastBlock
The last (de|en)crypted block


scratch

private byte[] scratch
An intermediate buffer.

Constructor Detail

CBC

CBC(gnu.javax.crypto.cipher.IBlockCipher underlyingCipher,
    int cipherBlockSize)
Package-private constructor for the factory class.


CBC

private CBC(CBC that)
Our constructor for cloning.

Method Detail

clone

public java.lang.Object clone()
Description copied from interface: gnu.javax.crypto.cipher.IBlockCipher

Returns a clone of this instance.

Specified by:
clone in interface gnu.javax.crypto.cipher.IBlockCipher
Specified by:
clone in class BaseMode

setup

public void setup()
Description copied from class: BaseMode
The initialisation phase of the concrete mode implementation.

Specified by:
setup in class BaseMode

teardown

public void teardown()
Description copied from class: BaseMode
The termination phase of the concrete mode implementation.

Specified by:
teardown in class BaseMode

encryptBlock

public void encryptBlock(byte[] in,
                         int i,
                         byte[] out,
                         int o)
Description copied from interface: gnu.javax.crypto.cipher.IBlockCipher

Encrypts exactly one block of plaintext.

Specified by:
encryptBlock in interface gnu.javax.crypto.cipher.IBlockCipher
Specified by:
encryptBlock in class BaseMode

decryptBlock

public void decryptBlock(byte[] in,
                         int i,
                         byte[] out,
                         int o)
Description copied from interface: gnu.javax.crypto.cipher.IBlockCipher

Decrypts exactly one block of ciphertext.

Specified by:
decryptBlock in interface gnu.javax.crypto.cipher.IBlockCipher
Specified by:
decryptBlock in class BaseMode