org.bouncycastle.crypto.macs

Class CMac

public class CMac extends Object implements Mac

CMAC - as specified at www.nuee.nagoya-u.ac.jp/labs/tiwata/omac/omac.html

CMAC is analogous to OMAC1 - see also en.wikipedia.org/wiki/CMAC

CMAC is a NIST recomendation - see csrc.nist.gov/CryptoToolkit/modes/800-38_Series_Publications/SP800-38B.pdf

CMAC/OMAC1 is a blockcipher-based message authentication code designed and analyzed by Tetsu Iwata and Kaoru Kurosawa.

CMAC/OMAC1 is a simple variant of the CBC MAC (Cipher Block Chaining Message Authentication Code). OMAC stands for One-Key CBC MAC.

It supports 128- or 64-bits block ciphers, with any key size, and returns a MAC with dimension less or equal to the block size of the underlying cipher.

Constructor Summary
CMac(BlockCipher cipher)
create a standard MAC based on a CBC block cipher (64 or 128 bit block).
CMac(BlockCipher cipher, int macSizeInBits)
create a standard MAC based on a block cipher with the size of the MAC been given in bits.
Method Summary
intdoFinal(byte[] out, int outOff)
StringgetAlgorithmName()
intgetMacSize()
voidinit(CipherParameters params)
voidreset()
Reset the mac generator.
voidupdate(byte in)
voidupdate(byte[] in, int inOff, int len)

Constructor Detail

CMac

public CMac(BlockCipher cipher)
create a standard MAC based on a CBC block cipher (64 or 128 bit block). This will produce an authentication code the length of the block size of the cipher.

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

CMac

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

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 and <= 128.

Method Detail

doFinal

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

getAlgorithmName

public String getAlgorithmName()

getMacSize

public int getMacSize()

init

public void init(CipherParameters params)

reset

public void reset()
Reset the mac generator.

update

public void update(byte in)

update

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