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cryptix.jce.provider.cipher
Class CAST5  

java.lang.Object
  javax.crypto.CipherSpi
      cryptix.jce.provider.cipher.BlockCipher
          cryptix.jce.provider.cipher.CAST5

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public final class CAST5

extends BlockCipher

CAST5 (a.k.a. CAST-128) in Java, as per RFC 2144.

The author, 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:

• Carlisle Adams, RFC 2144, May 1997.

Since:

Cryptix 2.2.2

Version:

$Revision: 1.7 $

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Field Summary
private static int	BLOCK_SIZE           Various constants
private  boolean	decrypt           We are in decrypt mode
private static int	DEFAULT_NOF_ROUNDS           Various constants
private  int	Km0           Masking session keys.
private  int	Km1           Masking session keys.
private  int	Km10           Masking session keys.
private  int	Km11           Masking session keys.
private  int	Km12           Masking session keys.
private  int	Km13           Masking session keys.
private  int	Km14           Masking session keys.
private  int	Km15           Masking session keys.
private  int	Km2           Masking session keys.
private  int	Km3           Masking session keys.
private  int	Km4           Masking session keys.
private  int	Km5           Masking session keys.
private  int	Km6           Masking session keys.
private  int	Km7           Masking session keys.
private  int	Km8           Masking session keys.
private  int	Km9           Masking session keys.
private  int	Kr0           Rotation session keys.
private  int	Kr1           Rotation session keys.
private  int	Kr10           Rotation session keys.
private  int	Kr11           Rotation session keys.
private  int	Kr12           Rotation session keys.
private  int	Kr13           Rotation session keys.
private  int	Kr14           Rotation session keys.
private  int	Kr15           Rotation session keys.
private  int	Kr2           Rotation session keys.
private  int	Kr3           Rotation session keys.
private  int	Kr4           Rotation session keys.
private  int	Kr5           Rotation session keys.
private  int	Kr6           Rotation session keys.
private  int	Kr7           Rotation session keys.
private  int	Kr8           Rotation session keys.
private  int	Kr9           Rotation session keys.
private static int	MAX_NOF_ROUNDS           Various constants
private static int	MIN_NOF_ROUNDS           Various constants
private  int	rounds           Number of rounds (depends on key length)
private static int[]	S0           8 S-boxes
private static int[]	S1           8 S-boxes
private static int[]	S2           8 S-boxes
private static int[]	S3           8 S-boxes
private static int[]	S4           8 S-boxes
private static int[]	S5           8 S-boxes
private static int[]	S6           8 S-boxes
private static int[]	S7           8 S-boxes
private static int[]	S8           8 S-boxes
private static java.lang.String	sS0           Compressed S-boxes.
private static java.lang.String	sS1           Compressed S-boxes.
private static java.lang.String	sS2           Compressed S-boxes.
private static java.lang.String	sS3           Compressed S-boxes.
private static java.lang.String	sS4           Compressed S-boxes.
private static java.lang.String	sS5           Compressed S-boxes.
private static java.lang.String	sS6           Compressed S-boxes.
private static java.lang.String	sS7           Compressed S-boxes.
private static java.lang.String	sS8           Compressed S-boxes.

 

Fields inherited from class cryptix.jce.provider.cipher.BlockCipher

 

Constructor Summary

CAST5()

 

Method Summary
private  void	blockDecrypt(byte[] in, int off, byte[] out, int outOff)           Decrypts a 64-bit block by applying the formulae and sub-keys in reverse order to that of the encryption.
private  void	blockEncrypt(byte[] in, int off, byte[] out, int outOff)           The full encryption algorithm is given in the following four steps.
protected  void	coreCrypt(byte[] in, int inOffset, byte[] out, int outOffset)           Encrypt or decrypt a single data block
protected  void	coreInit(java.security.Key key, boolean decrypt)           Initializes this cipher using the specified key.
private static int[]	expand(java.lang.String in)           Expand a String of compressed S-box data and return an S-box with uncompressed data.
private  int	f1(int I, int m, int r)
private  int	f2(int I, int m, int r)
private  int	f3(int I, int m, int r)
private  void	makeKey(java.security.Key key)           Expands a user key to a working CAST5 128-bit key --by padding it with 0x00 if it's shorter than 16 bytes-- and generates the masking and rotation keypairs for the block cipher.
private static int[]	unscramble(int x)           Assuming the input is a 32-bit block organised as: b31b30b29...b0, returns an array of 4 Java ints, containing from position 0 onward the values: {b31b30b29b28, b27b26b25b24, ...

 

Methods inherited from class cryptix.jce.provider.cipher.BlockCipher

clone, coreGetBlockSize, engineDoFinal, engineDoFinal, engineGetBlockSize, engineGetIV, engineGetKeySize, engineGetOutputSize, engineGetParameters, engineInit, engineInit, engineInit, engineSetMode, engineSetPadding, engineUpdate, engineUpdate

 

Methods inherited from class javax.crypto.CipherSpi

engineDoFinal, engineUnwrap, engineUpdate, engineWrap

 

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

 

Field Detail

MIN_NOF_ROUNDS

private static final int MIN_NOF_ROUNDS

Various constants

See Also:

Constant Field Values

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MAX_NOF_ROUNDS

private static final int MAX_NOF_ROUNDS

Various constants

See Also:

Constant Field Values

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BLOCK_SIZE

private static final int BLOCK_SIZE

Various constants

See Also:

Constant Field Values

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DEFAULT_NOF_ROUNDS

private static final int DEFAULT_NOF_ROUNDS

Various constants

See Also:

Constant Field Values

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sS0

private static java.lang.String sS0

Compressed S-boxes. Compiled size from 33K to 21K. See Blowfish.java for more info.

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sS1

private static java.lang.String sS1

Compressed S-boxes. Compiled size from 33K to 21K. See Blowfish.java for more info.

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sS2

private static java.lang.String sS2

Compressed S-boxes. Compiled size from 33K to 21K. See Blowfish.java for more info.

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sS3

private static java.lang.String sS3

Compressed S-boxes. Compiled size from 33K to 21K. See Blowfish.java for more info.

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sS4

private static java.lang.String sS4

Compressed S-boxes. Compiled size from 33K to 21K. See Blowfish.java for more info.

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sS5

private static java.lang.String sS5

Compressed S-boxes. Compiled size from 33K to 21K. See Blowfish.java for more info.

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sS6

private static java.lang.String sS6

Compressed S-boxes. Compiled size from 33K to 21K. See Blowfish.java for more info.

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sS7

private static java.lang.String sS7

Compressed S-boxes. Compiled size from 33K to 21K. See Blowfish.java for more info.

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sS8

private static java.lang.String sS8

Compressed S-boxes. Compiled size from 33K to 21K. See Blowfish.java for more info.

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S0

private static final int[] S0

8 S-boxes

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S1

private static final int[] S1

8 S-boxes

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S2

private static final int[] S2

8 S-boxes

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S3

private static final int[] S3

8 S-boxes

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S4

private static final int[] S4

8 S-boxes

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S5

private static final int[] S5

8 S-boxes

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S6

private static final int[] S6

8 S-boxes

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S7

private static final int[] S7

8 S-boxes

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S8

private static final int[] S8

8 S-boxes

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decrypt

private boolean decrypt

We are in decrypt mode

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rounds

private int rounds

Number of rounds (depends on key length)

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Km0

private int Km0

Masking session keys.

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Km1

private int Km1

Masking session keys.

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Km2

private int Km2

Masking session keys.

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Km3

private int Km3

Masking session keys.

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Km4

private int Km4

Masking session keys.

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Km5

private int Km5

Masking session keys.

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Km6

private int Km6

Masking session keys.

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Km7

private int Km7

Masking session keys.

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Km8

private int Km8

Masking session keys.

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Km9

private int Km9

Masking session keys.

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Km10

private int Km10

Masking session keys.

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Km11

private int Km11

Masking session keys.

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Km12

private int Km12

Masking session keys.

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Km13

private int Km13

Masking session keys.

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Km14

private int Km14

Masking session keys.

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Km15

private int Km15

Masking session keys.

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Kr0

private int Kr0

Rotation session keys.

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Kr1

private int Kr1

Rotation session keys.

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Kr2

private int Kr2

Rotation session keys.

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Kr3

private int Kr3

Rotation session keys.

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Kr4

private int Kr4

Rotation session keys.

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Kr5

private int Kr5

Rotation session keys.

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Kr6

private int Kr6

Rotation session keys.

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Kr7

private int Kr7

Rotation session keys.

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Kr8

private int Kr8

Rotation session keys.

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Kr9

private int Kr9

Rotation session keys.

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Kr10

private int Kr10

Rotation session keys.

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Kr11

private int Kr11

Rotation session keys.

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Kr12

private int Kr12

Rotation session keys.

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Kr13

private int Kr13

Rotation session keys.

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Kr14

private int Kr14

Rotation session keys.

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Kr15

private int Kr15

Rotation session keys.

Constructor Detail

CAST5

public CAST5()

Method Detail

expand

private static int[] expand(java.lang.String in)

Expand a String of compressed S-box data and return an S-box with uncompressed data.

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coreInit

protected void coreInit(java.security.Key key,
                        boolean decrypt)
                 throws java.security.InvalidKeyException

Initializes this cipher using the specified key.

Specified by:

coreInit in class BlockCipher

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coreCrypt

protected void coreCrypt(byte[] in,
                         int inOffset,
                         byte[] out,
                         int outOffset)

Encrypt or decrypt a single data block

Specified by:

coreCrypt in class BlockCipher

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makeKey

private void makeKey(java.security.Key key)
              throws java.security.InvalidKeyException

Expands a user key to a working CAST5 128-bit key --by padding it with 0x00 if it's shorter than 16 bytes-- and generates the masking and rotation keypairs for the block cipher.

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unscramble

private static final int[] unscramble(int x)

Assuming the input is a 32-bit block organised as: b31b30b29...b0, returns an array of 4 Java ints, containing from position 0 onward the values: {b31b30b29b28, b27b26b25b24, ... , b3b2b1b0}.

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blockEncrypt

private void blockEncrypt(byte[] in,
                          int off,
                          byte[] out,
                          int outOff)

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);
 

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blockDecrypt

private void blockDecrypt(byte[] in,
                          int off,
                          byte[] out,
                          int outOff)

Decrypts a 64-bit block by applying the formulae and sub-keys in reverse order to that of the encryption.

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f1

private final int f1(int I,
                     int m,
                     int r)

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f2

private final int f2(int I,
                     int m,
                     int r)

---

f3

private final int f3(int I,
                     int m,
                     int r)

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