org.spongycastle.crypto.macs

Class ISO9797Alg3Mac

java.lang.Object

org.spongycastle.crypto.macs.ISO9797Alg3Mac

All Implemented Interfaces:

Mac

public class ISO9797Alg3Mac
extends java.lang.Object
implements Mac

DES based CBC Block Cipher MAC according to ISO9797, algorithm 3 (ANSI X9.19 Retail MAC) This could as well be derived from CBCBlockCipherMac, but then the property mac in the base class must be changed to protected

Constructor Summary

Constructors

Constructor and Description
ISO9797Alg3Mac(BlockCipher cipher) create a Retail-MAC based on a CBC block cipher.
ISO9797Alg3Mac(BlockCipher cipher, BlockCipherPadding padding) create a Retail-MAC based on a CBC block cipher.
ISO9797Alg3Mac(BlockCipher cipher, int macSizeInBits) create a Retail-MAC based on a block cipher with the size of the MAC been given in bits.
ISO9797Alg3Mac(BlockCipher cipher, int macSizeInBits, BlockCipherPadding padding) create a standard MAC based on a block cipher with the size of the MAC been given in bits.

Method Summary

Modifier and Type	Method and Description
int	doFinal(byte[] out, int outOff) Compute the final stage of the MAC writing the output to the out parameter.
java.lang.String	getAlgorithmName() Return the name of the algorithm the MAC implements.
int	getMacSize() Return the block size for this MAC (in bytes).
void	init(CipherParameters params) Initialise the MAC.
void	reset() Reset the mac generator.
void	update(byte in) add a single byte to the mac for processing.
void	update(byte[] in, int inOff, int len)

Methods inherited from class java.lang.Object

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

Constructor Detail

ISO9797Alg3Mac

public ISO9797Alg3Mac(BlockCipher cipher)

create a Retail-MAC based on a CBC block cipher. This will produce an authentication code of the length of the block size of the cipher.

Parameters:

cipher - the cipher to be used as the basis of the MAC generation. This must be DESEngine.

ISO9797Alg3Mac

public ISO9797Alg3Mac(BlockCipher cipher,
                      BlockCipherPadding padding)

create a Retail-MAC based on a CBC block cipher. This will produce an authentication code of the length of the block size of the cipher.

Parameters:

cipher - the cipher to be used as the basis of the MAC generation.

padding - the padding to be used to complete the last block.

ISO9797Alg3Mac

public ISO9797Alg3Mac(BlockCipher cipher,
                      int macSizeInBits)

create a Retail-MAC based on a block cipher with the size of the MAC been given in bits. This class uses single DES CBC mode as the basis for the MAC generation.

Note: the size of the MAC must be at least 24 bits (FIPS Publication 81), or 16 bits if being used as a data authenticator (FIPS Publication 113), and in general should be less than the size of the block cipher as it reduces the chance of an exhaustive attack (see Handbook of Applied Cryptography).

Parameters:

cipher - the cipher to be used as the basis of the MAC generation.

macSizeInBits - the size of the MAC in bits, must be a multiple of 8.

ISO9797Alg3Mac

public ISO9797Alg3Mac(BlockCipher cipher,
                      int macSizeInBits,
                      BlockCipherPadding padding)

create a standard MAC based on a block cipher with the size of the MAC been given in bits. This class uses single DES CBC mode as the basis for the MAC generation. The final block is decrypted and then encrypted using the middle and right part of the key.

Note: the size of the MAC must be at least 24 bits (FIPS Publication 81), or 16 bits if being used as a data authenticator (FIPS Publication 113), and in general should be less than the size of the block cipher as it reduces the chance of an exhaustive attack (see Handbook of Applied Cryptography).

Parameters:

cipher - the cipher to be used as the basis of the MAC generation.

macSizeInBits - the size of the MAC in bits, must be a multiple of 8.

padding - the padding to be used to complete the last block.

Method Detail

getAlgorithmName

public java.lang.String getAlgorithmName()

Description copied from interface: Mac

Return the name of the algorithm the MAC implements.

Specified by:

getAlgorithmName in interface Mac

Returns:

the name of the algorithm the MAC implements.

init

public void init(CipherParameters params)

Description copied from interface: Mac

Initialise the MAC.

Specified by:

init in interface Mac

Parameters:

params - the key and other data required by the MAC.

getMacSize

public int getMacSize()

Description copied from interface: Mac

Return the block size for this MAC (in bytes).

Specified by:

getMacSize in interface Mac

Returns:

the block size for this MAC in bytes.

update

public void update(byte in)

Description copied from interface: Mac

add a single byte to the mac for processing.

Specified by:

update in interface Mac

Parameters:

in - the byte to be processed.

update

public void update(byte[] in,
                   int inOff,
                   int len)

Specified by:

update in interface Mac

Parameters:

in - the array containing the input.

inOff - the index in the array the data begins at.

len - the length of the input starting at inOff.

doFinal

public int doFinal(byte[] out,
                   int outOff)

Description copied from interface: Mac

Compute the final stage of the MAC writing the output to the out parameter.

doFinal leaves the MAC in the same state it was after the last init.

Specified by:

doFinal in interface Mac

Parameters:

out - the array the MAC is to be output to.

outOff - the offset into the out buffer the output is to start at.

reset

public void reset()

Reset the mac generator.

Specified by:

reset in interface Mac