cryptix.provider.cipher

Class CAST5

java.lang.Object

xjava.security.IJCE_Traceable

xjava.security.Cipher

cryptix.provider.cipher.CAST5

All Implemented Interfaces:

Parameterized, SymmetricCipher

public final class CAST5
extends Cipher
implements SymmetricCipher

A subclass of Cipher to implement the CAST5 (a.k.a. CAST-128) algorithm in Java, as per RFC 2144 dated May 1997.

In this RFC, Carlisle Adams (the CA in CAST, ST standing for Stafford Tavares) describes CAST5 as:

"...a DES-like Substitution-Permutation Network (SPN) cryptosystem which appears to have good resistance to differential cryptanalysis, linear cryptanalysis, and related-key cryptanalysis. This cipher also possesses a number of other desirable cryptographic properties, including avalanche, Strict Avalanche Criterion (SAC), Bit Independence Criterion (BIC), no complementation property, and an absence of weak and semi-weak keys."

CAST5 is a symmetric block cipher with a block-size of 8 bytes and a variable key-size of up to 128 bits. Its authors and their employer (Entrust Technologies, a Nortel majority-owned company) made it available worldwide on a royalty-free basis for commercial and non-commercial uses.

The CAST5 encryption algorithm has been designed to allow a key size that can vary from 40 bits to 128 bits, in 8-bit increments (that is, the allowable key sizes are 40, 48, 56, 64, ..., 112, 120, and 128 bits. For variable keysize operation, the specification is as follows:

1. For key sizes up to and including 80 bits (i.e., 40, 48, 56, 64, 72, and 80 bits), the algorithm is exactly as specified but uses 12 rounds instead of 16;
2. For key sizes greater than 80 bits, the algorithm uses the full 16 rounds;
3. For key sizes less than 128 bits, the key is padded with zero bytes (in the rightmost, or least significant, positions) out to 128 bits (since the CAST5 key schedule assumes an input key of 128 bits).

References:

1. Carlisle Adams, RFC 2144, May 1997.

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

$Revision: 1.6 $

Since:

Cryptix 2.2.2

Author:

Raif S. Naffah

Field Summary

Fields inherited from class xjava.security.Cipher

DECRYPT, ENCRYPT, UNINITIALIZED

Constructor Summary

Constructors

Constructor and Description
CAST5() Constructs a CAST5 cipher object, in the UNINITIALIZED state.

Method Summary

Modifier and Type	Method and Description
java.lang.Object	clone() Always throws a CloneNotSupportedException (cloning of ciphers is not supported for security reasons).
protected int	engineBlockSize() SPI: Returns the length of an input block, in bytes.
protected void	engineInitDecrypt(java.security.Key key) SPI: Initializes this cipher for decryption, using the specified key.
protected void	engineInitEncrypt(java.security.Key key) SPI: Initializes this cipher for encryption, using the specified key.
protected int	engineUpdate(byte[] in, int inOffset, int inLen, byte[] out, int outOffset) SPI: This is the main engine method for updating data.
protected void	finalize() Cleans up resources used by this instance, if necessary.
static LinkStatus	getLinkStatus() Gets an object representing the native linking status of this class.

Methods inherited from class xjava.security.Cipher

blockSize, crypt, crypt, crypt, doFinal, doFinal, doFinal, doFinal, engineCiphertextBlockSize, engineCrypt, engineGetParameter, engineInBufferSize, engineOutBufferSize, enginePlaintextBlockSize, engineSetPaddingScheme, engineSetParameter, getAlgorithm, getAlgorithms, getAlgorithms, getCiphertextBlockSize, getInputBlockSize, getInstance, getInstance, getInstance, getMode, getOutputBlockSize, getPadding, getPaddingScheme, getParameter, getPlaintextBlockSize, getProvider, getState, inBufferSize, inBufferSizeFinal, initDecrypt, initEncrypt, isPaddingBlockCipher, outBufferSize, outBufferSizeFinal, setParameter, toString, update, update, update, update

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

CAST5

public CAST5()

Constructs a CAST5 cipher object, in the UNINITIALIZED state. This calls the Cipher constructor with implBuffering false, implPadding false and the provider set to "Cryptix".

See Also:

java.security.Cipher#UNINITIALIZED

Method Detail

getLinkStatus

public static LinkStatus getLinkStatus()

Gets an object representing the native linking status of this class.

finalize

protected final void finalize()

Cleans up resources used by this instance, if necessary.

Overrides:

finalize in class java.lang.Object

clone

public final java.lang.Object clone()
                             throws java.lang.CloneNotSupportedException

Always throws a CloneNotSupportedException (cloning of ciphers is not supported for security reasons).

Overrides:

clone in class Cipher

Throws:

java.lang.CloneNotSupportedException - if the cipher is not cloneable.

engineBlockSize

protected int engineBlockSize()

SPI: Returns the length of an input block, in bytes.

Overrides:

engineBlockSize in class Cipher

Returns:

the length in bytes of an input block for this cipher.

engineInitEncrypt

protected void engineInitEncrypt(java.security.Key key)
                          throws java.security.KeyException

SPI: Initializes this cipher for encryption, using the specified key.

Specified by:

engineInitEncrypt in class Cipher

Parameters:

key - the key to use for encryption.

Throws:

java.security.KeyException - when one of the following occurs:

• The user key object is null;
• The decoded byte array form of the user key is zero long;
• The decoded user key is shorter than 40 bits or longer than 128 bits.

engineInitDecrypt

protected void engineInitDecrypt(java.security.Key key)
                          throws java.security.KeyException

SPI: Initializes this cipher for decryption, using the specified key.

Specified by:

engineInitDecrypt in class Cipher

Parameters:

key - the key to use for decryption.

Throws:

java.security.KeyException - when one of the following occurs:

• The user key object is null;
• The decoded byte array form of the user key is zero long;
• The decoded user key is shorter than 40 bits or longer than 128 bits.

engineUpdate

protected int engineUpdate(byte[] in,
                           int inOffset,
                           int inLen,
                           byte[] out,
                           int outOffset)

SPI: This is the main engine method for updating data.

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

Specified by:

engineUpdate in class Cipher

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.

Throws:

CryptixException - if the native library is being used, and it reports an error.