MacSpi

AI-generated Key Takeaways

• MacSpi is a Service Provider Interface (SPI) for the Mac class, defining methods for implementing Message Authentication Code (MAC) algorithms.

• Cryptographic service providers must implement all abstract methods of MacSpi to provide a specific MAC algorithm.

• MacSpi implementations can optionally support cloning for creating copies of the MAC object.

• Key methods include engineInit for initialization, engineUpdate for processing data, and engineDoFinal for completing the MAC computation.

• MacSpi provides methods to get the MAC length and to reset the MAC for further use while maintaining the secret key.

public abstract class MacSpi extends Object

This class defines the Service Provider Interface (SPI) for the Mac class. All the abstract methods in this class must be implemented by each cryptographic service provider who wishes to supply the implementation of a particular MAC algorithm.

Implementations are free to implement the Cloneable interface.

Public Constructor Summary

MacSpi()

Public Method Summary

Object

clone() Returns a clone if the implementation is cloneable.

Protected Method Summary

abstract byte[]	engineDoFinal() Completes the MAC computation and resets the MAC for further use, maintaining the secret key that the MAC was initialized with.
abstract int	engineGetMacLength() Returns the length of the MAC in bytes.
abstract void	engineInit(Key key, AlgorithmParameterSpec params) Initializes the MAC with the given (secret) key and algorithm parameters.
abstract void	engineReset() Resets the MAC for further use, maintaining the secret key that the MAC was initialized with.
void	engineUpdate(ByteBuffer input) Processes input.remaining() bytes in the ByteBuffer input, starting at input.position().
abstract void	engineUpdate(byte input) Processes the given byte.
abstract void	engineUpdate(byte[] input, int offset, int len) Processes the first len bytes in input, starting at offset inclusive.

Inherited Method Summary

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

Public Constructors

public MacSpi ()

Public Methods

public Object clone ()

Returns a clone if the implementation is cloneable.

Returns

• a clone if the implementation is cloneable.

Throws

CloneNotSupportedException	if this is called on an implementation that does not support Cloneable.

Protected Methods

protected abstract byte[] engineDoFinal ()

Completes the MAC computation and resets the MAC for further use, maintaining the secret key that the MAC was initialized with.

Returns

• the MAC result.

protected abstract int engineGetMacLength ()

Returns the length of the MAC in bytes.

Returns

• the MAC length in bytes.

protected abstract void engineInit (Key key, AlgorithmParameterSpec params)

Initializes the MAC with the given (secret) key and algorithm parameters.

Parameters

key	the (secret) key.
params	the algorithm parameters.

Throws

InvalidKeyException	if the given key is inappropriate for initializing this MAC.
InvalidAlgorithmParameterException	if the given algorithm parameters are inappropriate for this MAC.

protected abstract void engineReset ()

Resets the MAC for further use, maintaining the secret key that the MAC was initialized with.

protected void engineUpdate (ByteBuffer input)

Processes input.remaining() bytes in the ByteBuffer input, starting at input.position(). Upon return, the buffer's position will be equal to its limit; its limit will not have changed.

Subclasses should consider overriding this method if they can process ByteBuffers more efficiently than byte arrays.

Parameters

input	the ByteBuffer

protected abstract void engineUpdate (byte input)

Processes the given byte.

Parameters

input	the input byte to be processed.

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

Processes the first len bytes in input, starting at offset inclusive.

Parameters

input	the input buffer.
offset	the offset in input where the input starts.
len	the number of bytes to process.