Added in API level 1

Summary: Protected Ctors | Methods | Inherited Methods

Mac

public class Mac
extends Object implements Cloneable

java.lang.Object
↳	javax.crypto.Mac

---

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:

Algorithm	Supported API Levels
AESCMAC	31+
DESMAC	1-8
DESMAC/CFB8	1-8
DESedeMAC	1-8
DESedeMAC/CFB8	1-8
DESedeMAC64	1-8
DESwithISO9797	1-8
HmacMD5	1+
HmacSHA1	1+
HmacSHA224	1-8,22+
HmacSHA256	1+
HmacSHA384	1+
HmacSHA512	1+
ISO9797ALG3MAC	1-8
PBEwithHmacSHA	1+
PBEwithHmacSHA1	1+
PBEwithHmacSHA224	26-31
PBEwithHmacSHA256	26-31
PBEwithHmacSHA384	26-31
PBEwithHmacSHA512	26-31

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

Summary

Protected constructors
Mac(MacSpi macSpi, Provider provider, String algorithm) Creates a MAC object.

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

Inherited methods

From class java.lang.Object Object clone() Creates and returns a copy of this object. boolean equals(Object obj) Indicates whether some other object is "equal to" this one. void finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. final Class<?> getClass() Returns the runtime class of this Object. int hashCode() Returns a hash code value for the object. final void notify() Wakes up a single thread that is waiting on this object's monitor. final void notifyAll() Wakes up all threads that are waiting on this object's monitor. String toString() Returns a string representation of the object. final void wait(long timeoutMillis, int nanos) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait(long timeoutMillis) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait() Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

Protected constructors

Mac

Added in API level 1

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

Creates a MAC object.

Parameters
macSpi	MacSpi: the delegate
provider	Provider: the provider
algorithm	String: the algorithm

Public methods

clone

Added in API level 1

public final Object clone ()

Returns a clone if the provider implementation is cloneable.

Returns
Object	a clone if the provider implementation is cloneable.

Throws
CloneNotSupportedException	if this is called on a delegate that does not support Cloneable.

doFinal

Added in API level 1

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 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	byte: data in bytes

Returns
byte[]	the MAC result.

Throws
IllegalStateException	if this Mac has not been initialized.

doFinal

Added in API level 1

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 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	byte: the buffer where the MAC result is stored
outOffset	int: 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

Added in API level 1

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 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
byte[]	the MAC result.

Throws
IllegalStateException	if this Mac has not been initialized.

getAlgorithm

Added in API level 1

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
String	the algorithm name of this Mac object.

getInstance

Added in API level 1

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() method.

Parameters
algorithm	String: the standard name of the requested MAC algorithm. See the Mac section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.

Returns
Mac	the new Mac object.

Throws
NoSuchAlgorithmException	if no Provider supports a MacSpi implementation for the specified algorithm.

See also:

• Provider

getInstance

Added in API level 1

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() method.

Parameters
algorithm	String: the standard name of the requested MAC algorithm. See the Mac section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
provider	String: the name of the provider.

Returns
Mac	the new Mac object.

Throws
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.
IllegalArgumentException	if the provider is null or empty.

See also:

• Provider

getInstance

Added in API level 1

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.

Parameters
algorithm	String: the standard name of the requested MAC algorithm. See the Mac section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
provider	Provider: the provider.

Returns
Mac	the new Mac object.

Throws
NoSuchAlgorithmException	if a MacSpi implementation for the specified algorithm is not available from the specified Provider object.
IllegalArgumentException	if the provider is null.

See also:

• Provider

getMacLength

Added in API level 1

public final int getMacLength ()

Returns the length of the MAC in bytes.

Returns
int	the MAC length in bytes.

getProvider

Added in API level 1

public final Provider getProvider ()

Returns the provider of this Mac object.

Returns
Provider	the provider of this Mac object.

init

Added in API level 1

public final void init (Key key, 
                AlgorithmParameterSpec params)

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

Parameters
key	Key: the key.
params	AlgorithmParameterSpec: 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.

init

Added in API level 1

public final void init (Key key)

Initializes this Mac object with the given key.

Parameters
key	Key: the key.

Throws
InvalidKeyException	if the given key is inappropriate for initializing this MAC.

reset

Added in API level 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).

update

Added in API level 1

public final void update (byte[] input)

Processes the given array of bytes.

Parameters
input	byte: the array of bytes to be processed.

Throws
IllegalStateException	if this Mac has not been initialized.

update

Added in API level 1

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

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

Parameters
input	byte: the input buffer.
offset	int: the offset in input where the input starts.
len	int: the number of bytes to process.

Throws
IllegalStateException	if this Mac has not been initialized.

update

Added in API level 1

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	ByteBuffer: the ByteBuffer

Throws
IllegalStateException	if this Mac has not been initialized.

update

Added in API level 1

public final void update (byte input)

Processes the given byte.

Parameters
input	byte: the input byte to be processed.

Throws
IllegalStateException	if this Mac has not been initialized.