Cast5 (MA3 Api Crypto Provider GNU Module 2.3.11.8 API)

java.lang.Object
- gnu.crypto.cipher.BaseCipher
- - gnu.crypto.cipher.Cast5

All Implemented Interfaces:

IBlockCipher, java.lang.Cloneable
```
public class Cast5
extends BaseCipher
```
An implmenetation of the CAST5 (a.k.a. CAST-128) algorithm, as per RFC-2144, dated May 1997.

In this RFC, Carlisle Adams (the CA in CAST, ST stands 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. The CAST-128 Encryption Algorithm.
  Carlisle Adams.
Version:

$Revision: 1.1 $

Field Summary
- Fields inherited from class gnu.crypto.cipher.BaseCipher
  currentBlockSize, currentKey, defaultBlockSize, defaultKeySize, lock, name
- Fields inherited from interface gnu.crypto.cipher.IBlockCipher
  CIPHER_BLOCK_SIZE, KEY_MATERIAL

Constructor Summary

Constructors
Constructor and Description

Cast5()
Trivial 0-arguments constructor.

Constructors
Constructor and Description
`Cast5()` Trivial 0-arguments constructor.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`java.util.Iterator`	`blockSizes()` Returns an `Iterator` over the supported block sizes.
`java.lang.Object`	`clone()` Returns a clone of this instance.
`void`	`decrypt(byte[] in, int i, byte[] out, int j, java.lang.Object k, int bs)`
`void`	`encrypt(byte[] in, int i, byte[] out, int j, java.lang.Object k, int bs)` The full encryption algorithm is given in the following four steps.
`java.util.Iterator`	`keySizes()` Returns an `Iterator` over the supported key sizes.
`java.lang.Object`	`makeKey(byte[] uk, int bs)`
`boolean`	`selfTest()` A correctness test that consists of basic symmetric encryption / decryption test(s) for all supported block and key sizes, as well as one (1) variable key Known Answer Test (KAT).

Methods inherited from class gnu.crypto.cipher.BaseCipher
currentBlockSize, decryptBlock, defaultBlockSize, defaultKeySize, encryptBlock, init, name, reset, testKat, testKat

Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - Cast5
```
public Cast5()
```
    Trivial 0-arguments constructor.
- Method Detail
  - clone
```
public java.lang.Object clone()
```
    Description copied from interface: IBlockCipher
    
    Returns a clone of this instance.
    
    Specified by:
    
    clone in interface IBlockCipher
    
    Specified by:
    
    clone in class BaseCipher
    
    Returns:
    
    a clone copy of this instance.
  - blockSizes
```
public java.util.Iterator blockSizes()
```
    Description copied from interface: IBlockCipher
    
    Returns an Iterator over the supported block sizes. Each element returned by this object is an Integer.
    
    Returns:
    
    an Iterator over the supported block sizes.
  - keySizes
```
public java.util.Iterator keySizes()
```
    Description copied from interface: IBlockCipher
    
    Returns an Iterator over the supported key sizes. Each element returned by this object is an Integer.
    
    Returns:
    
    an Iterator over the supported key sizes.
  - makeKey
```
public java.lang.Object makeKey(byte[] uk,
                                int bs)
                         throws java.security.InvalidKeyException
```
    Throws:
    
    java.security.InvalidKeyException
  - encrypt
```
public void encrypt(byte[] in,
                    int i,
                    byte[] out,
                    int j,
                    java.lang.Object k,
                    int bs)
```
    The full encryption algorithm is given in the following four steps.
```
    INPUT:  plaintext m1...m64; key K = k1...k128.
    OUTPUT: ciphertext c1...c64.
 
```
    1. (key schedule) Compute 16 pairs of subkeys {Kmi, Kri} from a user key (see makeKey() method).
    2. (L0,R0) <-- (m1...m64). (Split the plaintext into left and right 32-bit halves L0 = m1...m32 and R0 = m33...m64.).
    3. (16 rounds) for i from 1 to 16, compute Li and Ri as follows:
      
      Li = Ri-1;
      
      Ri = Li-1 ^ F(Ri-1,Kmi,Kri), where F is defined in method F() -- f is of Type 1, Type 2, or Type 3, depending on i, and ^ being the bitwise XOR function.
    4. c1...c64 <-- (R16,L16). (Exchange final blocks L16, R16 and concatenate to form the ciphertext.)
    Decryption is identical to the encryption algorithm given above, except that the rounds (and therefore the subkey pairs) are used in reverse order to compute (L0,R0) from (R16,L16).
    
    Looking at the iterations/rounds in pairs we have:
```
    (1a)    Li = Ri-1;
    (1b)    Ri = Li-1 ^ Fi(Ri-1);
    (2a)    Li+1 = Ri;
    (2b)    Ri+1 = Li ^ Fi+1(Ri);
 
```
    which by substituting (2a) in (2b) becomes
```
    (2c)    Ri+1 = Li ^ Fi+1(Li+1);
 
```
    by substituting (1b) in (2a) and (1a) in (2c), we get:
```
    (3a)    Li+1 = Li-1 ^ Fi(Ri-1);
    (3b)    Ri+1 = Ri-1 ^ Fi+1(Li+1);
 
```
    Using only one couple of variables L and R, initialised to L0 and R0 respectively, the assignments for each pair of rounds become:
```
    (4a)    L ^= Fi(R);
    (4b)    R ^= Fi+1(L);
 
```
    Parameters:
    
    in - contains the plain-text 64-bit block.
    
    i - start index within input where data is considered.
    
    out - will contain the cipher-text block.
    
    j - index in out where cipher-text starts.
    
    k - the session key object.
    
    bs - the desired block size.
  - decrypt
```
public void decrypt(byte[] in,
                    int i,
                    byte[] out,
                    int j,
                    java.lang.Object k,
                    int bs)
```
  - selfTest
```
public boolean selfTest()
```
    Description copied from interface: IBlockCipher
    
    A correctness test that consists of basic symmetric encryption / decryption test(s) for all supported block and key sizes, as well as one (1) variable key Known Answer Test (KAT).
    
    Specified by:
    
    selfTest in interface IBlockCipher
    
    Overrides:
    
    selfTest in class BaseCipher
    
    Returns:
    
    true if the implementation passes simple correctness tests. Returns false otherwise.

Class Cast5

Field Summary

Fields inherited from class gnu.crypto.cipher.BaseCipher

Fields inherited from interface gnu.crypto.cipher.IBlockCipher

Constructor Summary

Method Summary

Methods inherited from class gnu.crypto.cipher.BaseCipher

Methods inherited from class java.lang.Object

Constructor Detail

Cast5

Method Detail

clone

blockSizes

keySizes

makeKey

encrypt

decrypt

selfTest