Bouncy Castle Cryptography Library 1.80 · org.bouncycastle.crypto.macs.CMac

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.

Field Summary

Modifier and Type	Field and Description
private byte[]	buf
private int	bufOff
private BlockCipher	cipher
private byte[]	Lu
private byte[]	Lu2
private byte[]	mac
private int	macSize
private byte[]	poly
private byte[]	ZEROES

Constructor Summary

Access	Constructor and Description
public	CMac(BlockCipher the cipher to be used as the basis of the MAC generation. cipher) create a standard MAC based on a CBC block cipher (64 or 128 bit block).
public	CMac(BlockCipher the cipher to be used as the basis of the MAC generation. cipher, int the size of the MAC in bits, must be a multiple of 8 and <= 128. macSizeInBits) 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
public int	doFinal(byte[] the array the MAC is to be output to. out, int the offset into the out buffer the output is to start at. outOff) Implements org.bouncycastle.crypto.Mac.doFinal. Compute the final stage of the MAC writing the output to the out parameter.
private byte[]	doubleLu(byte[] in)
public String	getAlgorithmName() Implements org.bouncycastle.crypto.Mac.getAlgorithmName. Return the name of the algorithm the MAC implements.
public int	getMacSize() Implements org.bouncycastle.crypto.Mac.getMacSize. Return the block size for this MAC (in bytes).
public void	init(CipherParameters the key and other data required by the MAC. params) Implements org.bouncycastle.crypto.Mac.init. Initialise the MAC.
private static byte[]	lookupPoly(int blockSizeLength)
public void	reset() Implements org.bouncycastle.crypto.Mac.reset. Reset the mac generator.
private static int	shiftLeft(byte[] block, byte[] output)
public void	update(byte the byte to be processed. in) Implements org.bouncycastle.crypto.Mac.update. add a single byte to the mac for processing.
public void	update(byte[] the array containing the input. in, int the index in the array the data begins at. inOff, int the length of the input starting at inOff. len) Implements org.bouncycastle.crypto.Mac.update.
pack-priv void	validate(CipherParameters params)

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

Field Detail

buf	back to summary
private byte[] buf

bufOff	back to summary
private int bufOff

cipher	back to summary
private BlockCipher cipher

Lu	back to summary
private byte[] Lu

Lu2	back to summary
private byte[] Lu2

mac	back to summary
private byte[] mac

macSize	back to summary
private int macSize

poly	back to summary
private byte[] poly

ZEROES	back to summary
private byte[] ZEROES

Constructor Detail

CMac	back to summary
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:BlockCipher the cipher to be used as the basis of the MAC generation.

CMac

back to summary

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

CMac	back to summary
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:BlockCipher the cipher to be used as the basis of the MAC generation. macSizeInBits:int the size of the MAC in bits, must be a multiple of 8 and <= 128.

CMac

back to summary

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:BlockCipher: the cipher to be used as the basis of the MAC generation.
macSizeInBits:int: the size of the MAC in bits, must be a multiple of 8 and <= 128.

Method Detail

doFinal	back to summary
public int doFinal(byte[] out, int outOff) Implements org.bouncycastle.crypto.Mac.doFinal. Doc from org.bouncycastle.crypto.Mac.doFinal. 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. Parameters out:byte[] the array the MAC is to be output to. outOff:int the offset into the out buffer the output is to start at.

doFinal

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

Implements org.bouncycastle.crypto.Mac.doFinal.

Doc from org.bouncycastle.crypto.Mac.doFinal.

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.

Parameters

out:byte[]: the array the MAC is to be output to.
outOff:int: the offset into the out buffer the output is to start at.

doubleLu	back to summary
private byte[] doubleLu(byte[] in)

getAlgorithmName	back to summary
public String getAlgorithmName() Implements org.bouncycastle.crypto.Mac.getAlgorithmName. Doc from org.bouncycastle.crypto.Mac.getAlgorithmName. Return the name of the algorithm the MAC implements. Returns:String the name of the algorithm the MAC implements.

getAlgorithmName

back to summary

public String getAlgorithmName()

Implements org.bouncycastle.crypto.Mac.getAlgorithmName.

Doc from org.bouncycastle.crypto.Mac.getAlgorithmName.

Return the name of the algorithm the MAC implements.

Returns:String: the name of the algorithm the MAC implements.

getMacSize	back to summary
public int getMacSize() Implements org.bouncycastle.crypto.Mac.getMacSize. Doc from org.bouncycastle.crypto.Mac.getMacSize. Return the block size for this MAC (in bytes). Returns:int the block size for this MAC in bytes.

getMacSize

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public int getMacSize()

Implements org.bouncycastle.crypto.Mac.getMacSize.

Doc from org.bouncycastle.crypto.Mac.getMacSize.

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

Returns:int: the block size for this MAC in bytes.

init	back to summary
public void init(CipherParameters params) Implements org.bouncycastle.crypto.Mac.init. Doc from org.bouncycastle.crypto.Mac.init. Initialise the MAC. Parameters params:CipherParameters the key and other data required by the MAC.

init

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public void init(CipherParameters params)

Implements org.bouncycastle.crypto.Mac.init.

Doc from org.bouncycastle.crypto.Mac.init.

Initialise the MAC.

Parameters

params:CipherParameters: the key and other data required by the MAC.

lookupPoly	back to summary
private static byte[] lookupPoly(int blockSizeLength)

reset	back to summary
public void reset() Implements org.bouncycastle.crypto.Mac.reset. Reset the mac generator.

reset

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public void reset()

Implements org.bouncycastle.crypto.Mac.reset.

Reset the mac generator.

shiftLeft	back to summary
private static int shiftLeft(byte[] block, byte[] output)

update	back to summary
public void update(byte in) Implements org.bouncycastle.crypto.Mac.update. Doc from org.bouncycastle.crypto.Mac.update. add a single byte to the mac for processing. Parameters in:byte the byte to be processed.

update

back to summary

public void update(byte in)

Implements org.bouncycastle.crypto.Mac.update.

Doc from org.bouncycastle.crypto.Mac.update.

add a single byte to the mac for processing.

Parameters

in:byte: the byte to be processed.

update	back to summary
public void update(byte[] in, int inOff, int len) Implements org.bouncycastle.crypto.Mac.update. Parameters in:byte[] Doc from org.bouncycastle.crypto.Mac.update. the array containing the input. inOff:int Doc from org.bouncycastle.crypto.Mac.update. the index in the array the data begins at. len:int Doc from org.bouncycastle.crypto.Mac.update. the length of the input starting at inOff.

update

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

Implements org.bouncycastle.crypto.Mac.update.

Parameters

in:byte[]

Doc from org.bouncycastle.crypto.Mac.update.

the array containing the input.

inOff:int

Doc from org.bouncycastle.crypto.Mac.update.

the index in the array the data begins at.

len:int

Doc from org.bouncycastle.crypto.Mac.update.

the length of the input starting at inOff.

validate	back to summary
pack-priv void validate(CipherParameters params)

public Class CMac

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail