javax.crypto

Class Mac

  1. java.lang.Object
  2. extended byjavax.crypto.Mac
All implemented interfaces:
java.lang.Cloneable

  1. public class Mac
  2. extends java.lang.Object
  3. implements java.lang.Cloneable
This class provides the functionality of a "Message Authentication Code" (MAC) algorithm.

A MAC provides a way to check the integrity of information transmitted over or stored in an unreliable medium, based on a secret key. Typically, message authentication codes are used between two parties that share a secret key in order to validate information transmitted between these parties.

A MAC mechanism that is based on cryptographic hash functions is referred to as HMAC. HMAC can be used with any cryptographic hash function, e.g., MD5 or SHA-1, in combination with a secret shared key. HMAC is specified in RFC 2104.

Since:
1.4
Version:
1.22, 01/06/04
Author:
Jan Luehe

Constructor Summary

Modifier Constructor and Description
  1. protected
Mac(MacSpi macSpi,java.security.Provider provider,java.lang.String algorithm)
Creates a MAC object.

Method Summary

Modifier and Type Method and Description
  1. java.lang.Object
clone()
Returns a clone if the provider implementation is cloneable.
  1. byte[]
doFinal()
Finishes the MAC operation.
  1. byte[]
doFinal(byte[] input)
Processes the given array of bytes and finishes the MAC operation.
  1. void
doFinal(byte[] output,int outOffset)
Finishes the MAC operation.
  1. java.lang.String
getAlgorithm()
Returns the algorithm name of this Mac object.
  1. static
  2. Mac
getInstance(java.lang.String algorithm)
Returns a Mac object that implements the specified MAC algorithm.
  1. static
  2. Mac
getInstance(java.lang.String algorithm,java.security.Provider provider)
Returns a Mac object that implements the specified MAC algorithm.
  1. static
  2. Mac
getInstance(java.lang.String algorithm,java.lang.String provider)
Returns a Mac object that implements the specified MAC algorithm.
  1. int
getMacLength()
Returns the length of the MAC in bytes.
  1. java.security.Provider
getProvider()
Returns the provider of this Mac object.
  1. void
init(java.security.Key key)
Initializes this Mac object with the given key.
  1. void
init(java.security.Key key,java.security.spec.AlgorithmParameterSpec params)
Initializes this Mac object with the given key and algorithm parameters.
  1. void
reset()
Resets this Mac object.
  1. void
update(byte input)
Processes the given byte.
  1. void
update(byte[] input)
Processes the given array of bytes.
  1. void
update(byte[] input,int offset,int len)
Processes the first len bytes in input, starting at offset inclusive.
  1. void
update(java.nio.ByteBuffer input)
Processes input.remaining() bytes in the ByteBuffer input, starting at input.position().
Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Mac

  1. protected Mac(MacSpi macSpi,
  2. java.security.Provider provider,
  3. java.lang.String algorithm)
Creates a MAC object.
Parameters:
macSpi - the delegate
provider - the provider
algorithm - the algorithm

Method Detail

getAlgorithm

  1. public final java.lang.String getAlgorithm( )
Returns the algorithm name of this Mac object.

This is the same name that was specified in one of the getInstance calls that created this Mac object.

Returns:
the algorithm name of this Mac object.

getInstance

  1. public static final Mac getInstance( java.lang.String algorithm)
  2. throws java.security.NoSuchAlgorithmException
Returns a Mac object that implements the specified MAC algorithm.

This method traverses the list of registered security Providers, starting with the most preferred Provider. A new Mac object encapsulating the MacSpi implementation from the first Provider that supports the specified algorithm is returned.

Note that the list of registered providers may be retrieved via the Security.getProviders() method.

Parameters:
algorithm - the standard name of the requested MAC algorithm. See Appendix A in the Java Cryptography Extension Reference Guide for information about standard algorithm names.
Returns:
the new Mac object.
Throws:
java.security.NoSuchAlgorithmException - if no Provider supports a MacSpi implementation for the specified algorithm.
See Also:
Provider

getInstance

  1. public static final Mac getInstance( java.lang.String algorithm,
  2. java.lang.String provider)
  3. throws java.security.NoSuchAlgorithmException
  4. java.security.NoSuchProviderException
Returns a Mac object that implements the specified MAC algorithm.

A new Mac object encapsulating the MacSpi implementation from the specified provider is returned. The specified provider must be registered in the security provider list.

Note that the list of registered providers may be retrieved via the Security.getProviders() method.

Parameters:
algorithm - the standard name of the requested MAC algorithm. See Appendix A in the Java Cryptography Extension Reference Guide for information about standard algorithm names.
provider - the name of the provider.
Returns:
the new Mac object.
Throws:
java.security.NoSuchAlgorithmException - if a MacSpi implementation for the specified algorithm is not available from the specified provider.
java.security.NoSuchProviderException - if the specified provider is not registered in the security provider list.
java.lang.IllegalArgumentException - if the provider is null or empty.
See Also:
Provider

getInstance

  1. public static final Mac getInstance( java.lang.String algorithm,
  2. java.security.Provider provider)
  3. throws java.security.NoSuchAlgorithmException
Returns a Mac object that implements the specified MAC algorithm.

A new Mac object encapsulating the MacSpi implementation from the specified Provider object is returned. Note that the specified Provider object does not have to be registered in the provider list.

Parameters:
algorithm - the standard name of the requested MAC algorithm. See Appendix A in the Java Cryptography Extension Reference Guide for information about standard algorithm names.
provider - the provider.
Returns:
the new Mac object.
Throws:
java.security.NoSuchAlgorithmException - if a MacSpi implementation for the specified algorithm is not available from the specified Provider object.
java.lang.IllegalArgumentException - if the provider is null.
See Also:
Provider

getProvider

  1. public final java.security.Provider getProvider( )
Returns the provider of this Mac object.
Returns:
the provider of this Mac object.

getMacLength

  1. public final int getMacLength()
Returns the length of the MAC in bytes.
Returns:
the MAC length in bytes.

init

  1. public final void init(java.security.Key key)
  2. throws java.security.InvalidKeyException
Initializes this Mac object with the given key.
Parameters:
key - the key.
Throws:
java.security.InvalidKeyException - if the given key is inappropriate for initializing this MAC.

init

  1. public final void init(java.security.Key key,
  2. java.security.spec.AlgorithmParameterSpec params)
  3. throws java.security.InvalidKeyException
  4. java.security.InvalidAlgorithmParameterException
Initializes this Mac object with the given key and algorithm parameters.
Parameters:
key - the key.
params - the algorithm parameters.
Throws:
java.security.InvalidKeyException - if the given key is inappropriate for initializing this MAC.
java.security.InvalidAlgorithmParameterException - if the given algorithm parameters are inappropriate for this MAC.

update

  1. public final void update(byte input)
  2. throws java.lang.IllegalStateException
Processes the given byte.
Parameters:
input - the input byte to be processed.
Throws:
java.lang.IllegalStateException - if this Mac has not been initialized.

update

  1. public final void update(byte[] input)
  2. throws java.lang.IllegalStateException
Processes the given array of bytes.
Parameters:
input - the array of bytes to be processed.
Throws:
java.lang.IllegalStateException - if this Mac has not been initialized.

update

  1. public final void update(byte[] input,
  2. int offset,
  3. int len)
  4. throws java.lang.IllegalStateException
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.
Throws:
java.lang.IllegalStateException - if this Mac has not been initialized.

update

  1. public final void update(java.nio.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.
Parameters:
input - the ByteBuffer
Throws:
java.lang.IllegalStateException - if this Mac has not been initialized.
Since:
1.5

doFinal

  1. public final byte[] doFinal()
  2. throws java.lang.IllegalStateException
Finishes the MAC operation.

A call to this method resets this Mac object to the state it was in when previously initialized via a call to init(Key) or init(Key, AlgorithmParameterSpec). That is, the object is reset and available to generate another MAC from the same key, if desired, via new calls to update and doFinal. (In order to reuse this Mac object with a different key, it must be reinitialized via a call to init(Key) or init(Key, AlgorithmParameterSpec).

Returns:
the MAC result.
Throws:
java.lang.IllegalStateException - if this Mac has not been initialized.

doFinal

  1. public final void doFinal(byte[] output,
  2. int outOffset)
  3. throws ShortBufferException
  4. java.lang.IllegalStateException
Finishes the MAC operation.

A call to this method resets this Mac object to the state it was in when previously initialized via a call to init(Key) or init(Key, AlgorithmParameterSpec). That is, the object is reset and available to generate another MAC from the same key, if desired, via new calls to update and doFinal. (In order to reuse this Mac object with a different key, it must be reinitialized via a call to init(Key) or init(Key, AlgorithmParameterSpec).

The MAC result is stored in output, starting at outOffset inclusive.

Parameters:
output - the buffer where the MAC result is stored
outOffset - the offset in output where the MAC is stored
Throws:
ShortBufferException - if the given output buffer is too small to hold the result
java.lang.IllegalStateException - if this Mac has not been initialized.

doFinal

  1. public final byte[] doFinal(byte[] input)
  2. throws java.lang.IllegalStateException
Processes the given array of bytes and finishes the MAC operation.

A call to this method resets this Mac object to the state it was in when previously initialized via a call to init(Key) or init(Key, AlgorithmParameterSpec). That is, the object is reset and available to generate another MAC from the same key, if desired, via new calls to update and doFinal. (In order to reuse this Mac object with a different key, it must be reinitialized via a call to init(Key) or init(Key, AlgorithmParameterSpec).

Parameters:
input - data in bytes
Returns:
the MAC result.
Throws:
java.lang.IllegalStateException - if this Mac has not been initialized.

reset

  1. public final void reset()
Resets this Mac object.

A call to this method resets this Mac object to the state it was in when previously initialized via a call to init(Key) or init(Key, AlgorithmParameterSpec). That is, the object is reset and available to generate another MAC from the same key, if desired, via new calls to update and doFinal. (In order to reuse this Mac object with a different key, it must be reinitialized via a call to init(Key) or init(Key, AlgorithmParameterSpec).


clone

  1. public final java.lang.Object clone( )
  2. throws java.lang.CloneNotSupportedException
Returns a clone if the provider implementation is cloneable.
Overrides:
clone in class java.lang.Object
Returns:
a clone if the provider implementation is cloneable.
Throws:
java.lang.CloneNotSupportedException - if this is called on a delegate that does not support Cloneable.