de.flexiprovider.api
Class Mac

java.lang.Object
  |
  +--javax.crypto.MacSpi
        |
        +--de.flexiprovider.api.Mac

Direct Known Subclasses:

CBCMac, CMac, HMac, TwoTrackMac

public abstract class Mac

extends javax.crypto.MacSpi

This class implements a "message authentication code" (MAC), a method to ensure the integrity of data transmitted between two parties who share a common secret key.

The best way to describe a MAC is as a keyed one-way hash function, which looks like:

D = MAC(K, M)

where K is the key, M is the message, and D is the resulting digest. One party will usually send the concatenation M || D to the other party, who will then verify D by computing D' in a similar fashion. If D == D', then the message is assumed to be authentic.

Author:

Martin Döring, Johannes Müller

Constructor Summary

Mac()

Method Summary

abstract byte[]	doFinal() Finishes the computation of a MAC and returns the digest.
byte[]	doFinal(byte[] input) Finishes the computation of a MAC with a final byte array (or computes a MAC over those bytes only) and returns the digest.
int	doFinal(byte[] output, int outOffset) Finishes the computation of a MAC and places the result into the given array.
protected byte[]	engineDoFinal()
protected int	engineGetMacLength()
protected void	engineInit(java.security.Key key, java.security.spec.AlgorithmParameterSpec params)
protected void	engineReset()
protected void	engineUpdate(byte input)
protected void	engineUpdate(byte[] input, int offset, int len)
abstract int	getMacLength() Return the MAC length.
void	init(SecretKey key) Initialize this MAC with a key and no parameters.
abstract void	init(SecretKey key, AlgorithmParameterSpec params) Initialize this MAC with a key and parameters.
abstract void	reset() Reset this instance.
abstract void	update(byte input) Update the computation with a single byte.
void	update(byte[] input) Update the computation with a byte array.
abstract void	update(byte[] input, int offset, int length) Update the computation with a portion of a byte array.

Methods inherited from class javax.crypto.MacSpi

clone

Methods inherited from class java.lang.Object

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

Constructor Detail

Mac

public Mac()

Method Detail

engineGetMacLength

protected final int engineGetMacLength()

Overrides:

engineGetMacLength in class javax.crypto.MacSpi

engineInit

protected void engineInit(java.security.Key key,
                          java.security.spec.AlgorithmParameterSpec params)
                   throws java.security.InvalidKeyException,
                          java.security.InvalidAlgorithmParameterException

Overrides:

engineInit in class javax.crypto.MacSpi

engineUpdate

protected final void engineUpdate(byte input)

Overrides:

engineUpdate in class javax.crypto.MacSpi

engineUpdate

protected final void engineUpdate(byte[] input,
                                  int offset,
                                  int len)

Overrides:

engineUpdate in class javax.crypto.MacSpi

engineDoFinal

protected final byte[] engineDoFinal()

Overrides:

engineDoFinal in class javax.crypto.MacSpi

engineReset

protected final void engineReset()

Overrides:

engineReset in class javax.crypto.MacSpi

getMacLength

public abstract int getMacLength()

Return the MAC length. This method is guaranteed to return a sane value only after the MAC has been initialized.

Returns:

the MAC length

init

public final void init(SecretKey key)
                throws InvalidKeyException

Initialize this MAC with a key and no parameters.

Parameters:

key - The key to initialize this instance with.

Throws:

InvalidKeyException - If the key is unacceptable.

init

public abstract void init(SecretKey key,
                          AlgorithmParameterSpec params)
                   throws InvalidAlgorithmParameterException,
                          InvalidKeyException

Initialize this MAC with a key and parameters.

Parameters:

key - The key to initialize this instance with.

params - The algorithm-specific parameters.

Throws:

InvalidAlgorithmParameterException - If the algorithm parameters are unacceptable.

InvalidKeyException - If the key is unacceptable.

update

public abstract void update(byte input)

Update the computation with a single byte.

Parameters:

input - The next byte.

update

public final void update(byte[] input)

Update the computation with a byte array.

Parameters:

input - The next bytes.

update

public abstract void update(byte[] input,
                            int offset,
                            int length)

Update the computation with a portion of a byte array.

Parameters:

input - The next bytes.

offset - The index in input to start.

length - The number of bytes to update.

doFinal

public abstract byte[] doFinal()

Finishes the computation of a MAC and returns the digest.

After this method succeeds, it may be used again as just after a call to init, and can compute another MAC using the same key and parameters.

Returns:

The message authentication code.

doFinal

public final byte[] doFinal(byte[] input)

Finishes the computation of a MAC with a final byte array (or computes a MAC over those bytes only) and returns the digest.

After this method succeeds, it may be used again as just after a call to init, and can compute another MAC using the same key and parameters.

Parameters:

input - The bytes to add.

Returns:

The message authentication code.

doFinal

public final int doFinal(byte[] output,
                         int outOffset)
                  throws ShortBufferException

Finishes the computation of a MAC and places the result into the given array.

After this method succeeds, it may be used again as just after a call to init, and can compute another MAC using the same key and parameters.

Parameters:

output - The destination for the result.

outOffset - The index in the output array to start.

Returns:

the number of bytes stored in output.

Throws:

ShortBufferException - If output is not large enough to hold the result.

reset

public abstract void reset()

Reset this instance. A call to this method returns this instance back to the state it was in just after it was initialized.