Mac  |  API reference  |  Android Developers (original) (raw)

public class Mac
extends [Object](/reference/java/lang/Object) implements[Cloneable](/reference/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.

Android provides the following Mac algorithms:

These algorithms are described in the Mac section of the Java Cryptography Architecture Standard Algorithm Name Documentation.

Summary

Protected constructors

Mac

protected Mac (MacSpi macSpi, Provider provider, String algorithm)

Creates a MAC object.

Public methods

clone

public final Object clone ()

Returns a clone if the provider implementation is cloneable.

doFinal

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

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 toinit(Key) orinit(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 anddoFinal. (In order to reuse this Mac object with a different key, it must be reinitialized via a call to init(Key) orinit(Key, AlgorithmParameterSpec).

doFinal

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

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 toinit(Key) orinit(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 anddoFinal. (In order to reuse this Mac object with a different key, it must be reinitialized via a call to init(Key) orinit(Key, AlgorithmParameterSpec).

The MAC result is stored in output, starting atoutOffset inclusive.

doFinal

public final byte[] doFinal ()

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 toinit(Key) orinit(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 anddoFinal. (In order to reuse this Mac object with a different key, it must be reinitialized via a call to init(Key) orinit(Key, AlgorithmParameterSpec).

getAlgorithm

public final String getAlgorithm ()

Returns the algorithm name of this Mac object.

This is the same name that was specified in one of thegetInstance calls that created thisMac object.

getInstance

public static final Mac getInstance (String algorithm)

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()](/reference/java/security/Security#getProviders%28%29) method.

getInstance

public static final Mac getInstance (String algorithm, String provider)

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()](/reference/java/security/Security#getProviders%28%29) method.

getInstance

public static final Mac getInstance (String algorithm, Provider provider)

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.

getMacLength

public final int getMacLength ()

Returns the length of the MAC in bytes.

getProvider

public final Provider getProvider ()

Returns the provider of this Mac object.

init

public final void init (Key key, AlgorithmParameterSpec params)

Initializes this Mac object with the given key and algorithm parameters.

init

public final void init (Key key)

Initializes this Mac object with the given key.

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 toinit(Key) orinit(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 anddoFinal. (In order to reuse this Mac object with a different key, it must be reinitialized via a call to init(Key) orinit(Key, AlgorithmParameterSpec).

update

public final void update (byte[] input)

Processes the given array of bytes.

update

public final void update (byte[] input, int offset, int len)

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

update

public final void update (ByteBuffer input)

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

update

public final void update (byte input)

Processes the given byte.