All Packages  Class Hierarchy  This Package  Previous  Next  Index

Class javax.crypto.Mac

java.lang.Object
   |
   +----javax.crypto.Mac

public class Mac
extends Object
This class provides the functionality of a "message authentication code" (MAC).

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.


Constructor Index

 o Mac(MacSpi, Provider, String)
Creates a MAC object.

Method Index

 o clone()
Returns a clone if the provider implementation is cloneable.
 o doFinal()
Completes this MAC computation and resets this Mac object for further MAC computations with the same secret key.
 o doFinal(byte[])
Processes the given array of bytes to complete this MAC computation and resets this Mac object for further MAC computations with the same secret key.
 o doFinal(byte[], int)
Completes this MAC computation and resets this Mac object for further MAC computations with the same secret key.
 o getAlgorithm()
Returns the standard name of the MAC algorithm.
 o getInstance(String)
Generates an Mac object that implements the specified MAC algorithm.
 o getInstance(String, String)
Generates an Mac object for the specified MAC algorithm from the specified provider.
 o getMacLength()
Returns the length of the MAC in bytes.
 o getProvider()
Returns the provider of this Mac object.
 o init(Key)
Initialises this Mac object with the given (secret) key.
 o init(Key, AlgorithmParameterSpec)
Initialises this Mac object with the given (secret) key and algorithm parameters.
 o reset()
Resets this Mac object for further MAC computations with the same secret key.
 o update(byte)
Processes the given byte.
 o update(byte[])
Processes the given array of bytes.
 o update(byte[], int, int)
Processes the first len bytes in input, starting at offset.

Constructors

 o Mac
 protected Mac(MacSpi macSpi,
               Provider provider,
               String algorithm)
Creates a MAC object.

Parameters:
macSpi - the delegate
provider - the provider
algorithm - the algorithm

Methods

 o getAlgorithm
 public final String getAlgorithm()
Returns the standard name of the MAC algorithm. See Appendix A in the Java Cryptography Extension API Specification & Reference for information about standard algorithm names.

Returns:
the standard algorithm name.
 o getInstance
 public static final Mac getInstance(String algorithm) throws NoSuchAlgorithmException
Generates an Mac object that implements the specified MAC algorithm. If the default provider package provides an implementation of the requested MAC algorithm, an instance of Mac containing that implementation is returned. If the algorithm is not available in the default provider package, other provider packages are searched.

Parameters:
algorithm - the standard name of the requested MAC algorithm. See Appendix A in the Java Cryptography Extension API Specification & Reference for information about standard algorithm names.
Returns:
the new Mac object.
Throws: NoSuchAlgorithmException
if the requested MAC algorithm is not available.
 o getInstance
 public static final Mac getInstance(String algorithm,
                                     String provider) throws NoSuchAlgorithmException, NoSuchProviderException
Generates an Mac object for the specified MAC algorithm from the specified provider.

Parameters:
algorithm - the standard name of the requested MAC algorithm. See Appendix A in the Java Cryptography Extension API Specification & Reference for information about standard algorithm names.
provider - the name of the provider.
Returns:
the new Mac object.
Throws: NoSuchAlgorithmException
if the requested MAC algorithm is not available from the provider.
Throws: NoSuchProviderException
if the requested provider is not available.
See Also:
Provider
 o getProvider
 public final Provider getProvider()
Returns the provider of this Mac object.

Parameters:
the - provider of this Mac object.
 o getMacLength
 public final int getMacLength()
Returns the length of the MAC in bytes.

Returns:
the MAC length in bytes.
 o init
 public final void init(Key key) throws InvalidKeyException
Initialises this Mac object with the given (secret) key.

Returns:
key the (secret) key.
Throws: InvalidKeyException
if the given key is inappropriate for initialising this MAC.
 o init
 public final void init(Key key,
                        AlgorithmParameterSpec params) throws InvalidKeyException, InvalidAlgorithmParameterException
Initialises this Mac object 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 initialising this MAC.
Throws: InvalidAlgorithmParameterException
if the given algorithm parameters are inappropriate for this MAC.
 o update
 public final void update(byte input) throws IllegalStateException
Processes the given byte.

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

Parameters:
input - the array of bytes to be processed.
Throws: IllegalStateException
if this Mac has not been initialised.
 o update
 public final void update(byte input[],
                          int offset,
                          int len) throws IllegalStateException
Processes the first len bytes in input, starting at offset.

Parameters:
input - the input buffer.
offset - the offset in input where the input starts.
len - the number of bytes to process.
Throws: IllegalStateException
if this Mac has not been initialised.
 o doFinal
 public final byte[] doFinal() throws IllegalStateException
Completes this MAC computation and resets this Mac object for further MAC computations with the same secret key. (In order to reuse this Mac object with a different secret key, init must be called after this call has completed.)

Returns:
the MAC result.
Throws: IllegalStateException
if this Mac has not been initialised.
 o doFinal
 public final void doFinal(byte output[],
                           int outOffset) throws ShortBufferException, IllegalStateException
Completes this MAC computation and resets this Mac object for further MAC computations with the same secret key. (In order to reuse this Mac object with a different secret key, init must be called after this call has completed.) The MAC result is stored in output, starting at outOffset.

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
Throws: IllegalStateException
if this Mac has not been initialized.
 o doFinal
 public final byte[] doFinal(byte input[]) throws IllegalStateException
Processes the given array of bytes to complete this MAC computation and resets this Mac object for further MAC computations with the same secret key. (In order to reuse this Mac object with a different secret key, init must be called after this call has completed.)

Returns:
the MAC result.
Throws: IllegalStateException
if this Mac has not been initialised.
 o reset
 public final void reset()
Resets this Mac object for further MAC computations with the same secret key. (In order to reuse this Mac object with a different secret key, init must be called after this call has completed.)

 o clone
 public final Object clone() throws CloneNotSupportedException
Returns a clone if the provider implementation is cloneable.

Returns:
a clone if the provider implementation is cloneable.
Throws: CloneNotSupportedException
if this is called on a delegate that does not support Cloneable.
Overrides:
clone in class Object

All Packages  Class Hierarchy  This Package  Previous  Next  Index