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:
- 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;
- For key sizes greater than 80 bits, the algorithm uses the full 16
rounds;
- 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:
- Carlisle Adams,
RFC 2144, May 1997.
Copyright © 1997
Systemics Ltd on behalf of the
Cryptix Development Team.
All rights reserved.
$Revision: 1.6 $
clone
public final Object clone()
throws CloneNotSupportedException
Always throws a CloneNotSupportedException (cloning of ciphers is not
supported for security reasons).
- clone in interface Cipher
engineBlockSize
protected int engineBlockSize()
SPI: Returns the length of an input block, in bytes.
- engineBlockSize in interface Cipher
- the length in bytes of an input block for this cipher.
engineInitDecrypt
protected void engineInitDecrypt(Key key)
throws KeyException
SPI: Initializes this cipher for decryption, using the
specified key.
- engineInitDecrypt in interface Cipher
key
- the key to use for decryption.
engineInitEncrypt
protected void engineInitEncrypt(Key key)
throws KeyException
SPI: Initializes this cipher for encryption, using the
specified key.
- engineInitEncrypt in interface Cipher
key
- the key to use for encryption.
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.
- engineUpdate in interface Cipher
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.
- the number of bytes written.
finalize
protected final void finalize()
Cleans up resources used by this instance, if necessary.
getLinkStatus
public static LinkStatus getLinkStatus()
Gets an object representing the native linking status of this class.