org.bouncycastle.crypto.macs

Class CBCBlockCipherMac

Implemented Interfaces:
Mac

public class CBCBlockCipherMac
extends java.lang.Object
implements Mac

standard CBC Block Cipher MAC - if no padding is specified the default of pad of zeroes is used.

Constructor Summary

CBCBlockCipherMac(BlockCipher cipher)
create a standard MAC based on a CBC block cipher.
CBCBlockCipherMac(BlockCipher cipher, int macSizeInBits)
create a standard MAC based on a block cipher with the size of the MAC been given in bits.
CBCBlockCipherMac(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.
CBCBlockCipherMac(BlockCipher cipher, BlockCipherPadding padding)
create a standard MAC based on a CBC block cipher.

Method Summary

int
doFinal(byte[] out, int outOff)
Compute the final statge of the MAC writing the output to the out parameter.
String
getAlgorithmName()
Return the name of the algorithm the MAC implements.
int
getMacSize()
Return the block size for this cipher (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)

Constructor Details

CBCBlockCipherMac

public CBCBlockCipherMac(BlockCipher cipher)
create a standard MAC based on a CBC block cipher. This will produce an authentication code half the length of the block size of the cipher.

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


CBCBlockCipherMac

public CBCBlockCipherMac(BlockCipher cipher,
                         int macSizeInBits)
create a standard MAC based on a block cipher with the size of the MAC been given in bits. This class uses 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.


CBCBlockCipherMac

public CBCBlockCipherMac(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 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.
padding - the padding to be used to complete the last block.


CBCBlockCipherMac

public CBCBlockCipherMac(BlockCipher cipher,
                         BlockCipherPadding padding)
create a standard MAC based on a CBC block cipher. This will produce an authentication code half 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.

Method Details

doFinal

public int doFinal(byte[] out,
                   int outOff)
Compute the final statge 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.


getAlgorithmName

public String getAlgorithmName()
Return the name of the algorithm the MAC implements.
Specified by:
getAlgorithmName in interface Mac

Returns:
the name of the algorithm the MAC implements.


getMacSize

public int getMacSize()
Return the block size for this cipher (in bytes).
Specified by:
getMacSize in interface Mac

Returns:
the block size for this cipher in bytes.


init

public void init(CipherParameters params)
Initialise the MAC.
Specified by:
init in interface Mac

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


reset

public void reset()
Reset the mac generator.
Specified by:
reset in interface Mac


update

public void update(byte in)
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.