cryptix.provider.mode

Class CBC

public class CBC extends FeedbackMode

Implements a block cipher in CBC mode. The block size is the same as that of the underlying cipher.

References:

  1. Bruce Schneier, "Section 9.3 Cipher Block Chaining Mode," and "Section 9.11 Choosing a Cipher Mode," Applied Cryptography, 2nd edition, John Wiley & Sons, 1996.

  2. sci.crypt FAQ, "Part 5: Product Ciphers," ftp://ftp.rtfm.mit.edu/pub/usenet/news.answers/cryptography-faq/part05.

  3. National Bureau of Standards (now NIST), "DES Modes of Operation," NBS FIPS PUB 81, U.S. Department of Commerce, December 1980.

Copyright © 1997, 1998 Systemics Ltd on behalf of the Cryptix Development Team.
All rights reserved.

$Revision: 1.7 $

Since: Cryptix 2.2.2

Author: David Hopwood Raif S. Naffah

Field Summary
protected byte[]xorBlock
Temporary buffer to hold input bytes when there's not enough of them to cipher.
Constructor Summary
CBC()
Constructs a CBC cipher, assuming that the IV will be provided via setInitializationVector.
CBC(Cipher cipher)
Constructs a CBC cipher, assuming that the IV will be provided via setInitializationVector.
CBC(Cipher cipher, byte[] iv)
Constructs a CBC cipher, using an initialization vector provided in the constructor.
Method Summary
protected intengineBlockSize()
protected voidengineInitDecrypt(Key newkey)
protected voidengineInitEncrypt(Key newkey)
protected voidengineSetCipher(Cipher cipher)
protected intengineUpdate(byte[] in, int inOffset, int inLen, byte[] out, int outOffset)
SPI: This is the main engine method for updating data.

Field Detail

xorBlock

protected byte[] xorBlock
Temporary buffer to hold input bytes when there's not enough of them to cipher.

Constructor Detail

CBC

public CBC()
Constructs a CBC cipher, assuming that the IV will be provided via setInitializationVector.

The IV value should be random, but unlike CFB mode, it is not absolutely required to be unique.

CBC

public CBC(Cipher cipher)
Constructs a CBC cipher, assuming that the IV will be provided via setInitializationVector. See the previous constructor for more details.

Parameters: cipher the cipher object to use in CBC mode.

Throws: NullPointerException if cipher == null IllegalBlockSizeException if cipher.getPlaintextBlockSize() != cipher.getCiphertextBlockSize()

CBC

public CBC(Cipher cipher, byte[] iv)
Constructs a CBC cipher, using an initialization vector provided in the constructor.

For CBC mode the IV value should be random, but unlike CFB mode, it is not absolutely required to be unique.

Parameters: cipher the block cipher to use iv the initial value for the shift register (IV)

Throws: NullPointerException if cipher == null

Method Detail

engineBlockSize

protected int engineBlockSize()

engineInitDecrypt

protected void engineInitDecrypt(Key newkey)

engineInitEncrypt

protected void engineInitEncrypt(Key newkey)

engineSetCipher

protected void engineSetCipher(Cipher cipher)

engineUpdate

protected int engineUpdate(byte[] in, int inOffset, int inLen, byte[] out, int outOffset)
SPI: This is the main engine method for updating data. It may be called with any size of input.

in and out may be the same array, and the input and output regions may overlap.

Parameters: in the input data. inOffset the offset into in specifying where the data starts. inLen the length of the subarray. out the output array. outOffset the offset indicating where to start writing into the out array.

Returns: the number of bytes written.