Module java.base
Package javax.crypto

Class Mac

java.lang.Object
javax.crypto.Mac
All Implemented Interfaces:
Cloneable
public class Mac
extends Object
implements 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., SHA256 or SHA384, in combination with a secret shared key. HMAC is specified in RFC 2104.

Every implementation of the Java platform is required to support the following standard Mac algorithms:

  • HmacSHA1
  • HmacSHA256
These algorithms are described in the Mac section of the Java Security Standard Algorithm Names Specification. Consult the release documentation for your implementation to see if any other algorithms are supported.

Since:
1.4

  • Constructor Summary

    Constructors 
    Modifier Constructor Description
    protected Mac​(MacSpi macSpi, Provider provider, String algorithm)
    Creates a MAC object.

  • Method Summary

    Modifier and Type Method Description
    Object clone()
    Returns a clone if the provider implementation is cloneable.
    byte[] doFinal()
    Finishes the MAC operation.
    byte[] doFinal​(byte[] input)
    Processes the given array of bytes and finishes the MAC operation.
    void doFinal​(byte[] output, int outOffset)
    Finishes the MAC operation.
    String getAlgorithm()
    Returns the algorithm name of this Mac object.
    static Mac getInstance​(String algorithm)
    Returns a Mac object that implements the specified MAC algorithm.
    static Mac getInstance​(String algorithm, String provider)
    Returns a Mac object that implements the specified MAC algorithm.
    static Mac getInstance​(String algorithm, Provider provider)
    Returns a Mac object that implements the specified MAC algorithm.
    int getMacLength()
    Returns the length of the MAC in bytes.
    Provider getProvider()
    Returns the provider of this Mac object.
    void init​(Key key)
    Initializes this Mac object with the given key.
    void init​(Key key, AlgorithmParameterSpec params)
    Initializes this Mac object with the given key and algorithm parameters.
    void reset()
    Resets this Mac object.
    void update​(byte input)
    Processes the given byte.
    void update​(byte[] input)
    Processes the given array of bytes.
    void update​(byte[] input, int offset, int len)
    Processes the first len bytes in input, starting at offset inclusive.
    void update​(ByteBuffer input)
    Processes input.remaining() bytes in the ByteBuffer input, starting at input.position().

    Methods declared in class java.lang.Object

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

  • Constructor Details

    • Mac

      protected Mac​(MacSpi macSpi, Provider provider, String algorithm)
      Creates a MAC object.
      Parameters:
      macSpi - the delegate
      provider - the provider
      algorithm - the algorithm

  • Method Details

    • getAlgorithm

      public final 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

      public static final Mac getInstance​(String algorithm) throws 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.

      Implementation Note:
      The JDK Reference Implementation additionally uses the jdk.security.provider.preferred Security property to determine the preferred provider order for the specified algorithm. This may be different than the order of providers returned by Security.getProviders().
      Parameters:
      algorithm - the standard name of the requested MAC algorithm. See the Mac section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.
      Returns:
      the new Mac object
      Throws:
      NoSuchAlgorithmException - if no Provider supports a MacSpi implementation for the specified algorithm
      NullPointerException - if algorithm is null
      See Also:
      Provider

    • getInstance

      public static final Mac getInstance​(String algorithm, String provider) throws NoSuchAlgorithmException, 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 the Mac section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.
      provider - the name of the provider.
      Returns:
      the new Mac object
      Throws:
      IllegalArgumentException - if the provider is null or empty
      NoSuchAlgorithmException - if a MacSpi implementation for the specified algorithm is not available from the specified provider
      NoSuchProviderException - if the specified provider is not registered in the security provider list
      NullPointerException - if algorithm is null
      See Also:
      Provider

    • getInstance

      public static final Mac getInstance​(String algorithm, Provider provider) throws 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 the Mac section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.
      provider - the provider.
      Returns:
      the new Mac object
      Throws:
      IllegalArgumentException - if the provider is null
      NoSuchAlgorithmException - if a MacSpi implementation for the specified algorithm is not available from the specified Provider object
      NullPointerException - if algorithm is null
      See Also:
      Provider

    • getProvider

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

    • getMacLength

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

    • init

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

    • init

      public final void init​(Key key, AlgorithmParameterSpec params) throws InvalidKeyException, InvalidAlgorithmParameterException
      Initializes this Mac object with the given key and algorithm parameters.
      Parameters:
      key - the 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.

    • 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 initialized.

    • 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 initialized.

    • update

      public final void update​(byte[] input, int offset, int len) throws 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:
      IllegalStateException - if this Mac has not been initialized.

    • update

      public final void update​(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:
      IllegalStateException - if this Mac has not been initialized.
      Since:
      1.5

    • doFinal

      public final byte[] doFinal() throws 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:
      IllegalStateException - if this Mac has not been initialized.

    • doFinal

      public final void doFinal​(byte[] output, int outOffset) throws ShortBufferException, 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
      IllegalStateException - if this Mac has not been initialized.

    • doFinal

      public final byte[] doFinal​(byte[] input) throws 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:
      IllegalStateException - if this Mac has not been initialized.

    • reset

      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

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