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Class cryptix.provider.cipher.CAST5
java.lang.Object
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+----java.security.IJCE_Traceable
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+----java.security.Cipher
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+----cryptix.provider.cipher.CAST5
- 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:
- 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: 1.3 $
- Author:
- Raif S. Naffah
-
CAST5()
- Constructs a CAST5 cipher object, in the UNINITIALIZED state.
-
clone()
- Always throws a CloneNotSupportedException (cloning of ciphers is not
supported for security reasons).
-
engineBlockSize()
- SPI: Returns the length of an input block, in bytes.
-
engineInitDecrypt(Key)
- SPI: Initializes this cipher for decryption, using the
specified key.
-
engineInitEncrypt(Key)
- SPI: Initializes this cipher for encryption, using the
specified key.
-
engineUpdate(byte[], int, int, byte[], int)
- SPI: This is the main engine method for updating data.
-
finalize()
- Cleans up resources used by this instance, if necessary.
-
getLinkStatus()
- Gets an object representing the native linking status of this class.
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:
- UNINITIALIZED
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 Object
clone
public final Object clone() throws CloneNotSupportedException
- Always throws a CloneNotSupportedException (cloning of ciphers is not
supported for security reasons).
- Overrides:
- clone in class Cipher
engineBlockSize
protected int engineBlockSize()
- SPI: Returns the length of an input block, in bytes.
- Returns:
- the length in bytes of an input block for this cipher.
- Overrides:
- engineBlockSize in class Cipher
engineInitEncrypt
protected void engineInitEncrypt(Key key) throws KeyException
- SPI: Initializes this cipher for encryption, using the
specified key.
- Parameters:
- key - the key to use for encryption.
- Throws: 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.
- Overrides:
- engineInitEncrypt in class Cipher
engineInitDecrypt
protected void engineInitDecrypt(Key key) throws KeyException
- SPI: Initializes this cipher for decryption, using the
specified key.
- Parameters:
- key - the key to use for decryption.
- Throws: 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.
- Overrides:
- engineInitDecrypt in class 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.
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.
- Throws: CryptixException
- if the native library is being used, and it
reports an error.
- Overrides:
- engineUpdate in class Cipher
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