Mac

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., MD5 or SHA-1, in combination with a secret shared key. HMAC is specified in RFC 2104.

Android provides the following Mac algorithms

Name Supported (API Levels)
DESedeMAC 1–8
DESedeMAC/CFB8 1–8
DESedeMAC64 1–8
DESMAC 1–8
DESMAC/CFB8 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+
These algorithms are described in the Mac section of the Java Cryptography Architecture Standard Algorithm Name Documentation.

Protected Constructor Summary

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

Public Method Summary

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.
final static Mac
getInstance(String algorithm)
Returns a Mac object that implements the specified MAC algorithm.
final static Mac
getInstance(String algorithm, String provider)
Returns a Mac object that implements the specified MAC algorithm.
final static 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 Method Summary

Protected Constructors

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

Creates a MAC object.

Parameters
macSpi the delegate
provider the provider
algorithm the algorithm

Public Methods

public final Object clone ()

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.

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 data in bytes
Returns
  • the MAC result.
Throws
IllegalStateException if this Mac has not been initialized.

public final void