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java.lang.Objectjavax.crypto.Mac
public class 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.
Field Summary | |
---|---|
private String |
algorithm_
the algorithm used by this instance. |
private boolean |
init_
States wether this cipher has been initialised. |
private MacSpi |
macSpi_
The MAC used this instance. |
private Provider |
provider_
The provider used by this instance. |
Constructor Summary | |
---|---|
protected |
Mac(MacSpi macSpi,
Provider provider,
String algorithm)
Creates a MAC object. |
Method Summary | |
---|---|
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)
Generates an Mac object that implements the specified MAC
algorithm. |
static Mac |
getInstance(String algorithm,
Provider provider)
Generates an Mac object for the specified MAC algorithm
from the specified provider. |
static Mac |
getInstance(String algorithm,
String provider)
Generates an Mac object for the specified MAC algorithm
from the specified provider. |
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 inherited from class java.lang.Object |
---|
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
---|
private Provider provider_
private boolean init_
private String algorithm_
private MacSpi macSpi_
Constructor Detail |
---|
protected Mac(MacSpi macSpi, Provider provider, String algorithm)
macSpi
- the delegate.provider
- the provider.algorithm
- the algorithm.Method Detail |
---|
public final String getAlgorithm()
Mac
object.
This is the same name that was specified in one of the
getInstance
calls that created this Mac
object.
Mac
object.public static final Mac getInstance(String algorithm) throws NoSuchAlgorithmException
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.
algorithm
- the standard name of the requested MAC algorithm.
See Appendix A in the
Java Cryptography Extension Reference Guide for information
about standard algorithm names.
Mac
object.
NoSuchAlgorithmException
- if the specified algorithm is not
available in the default provider package or any of the other
provider packages that were searched.public static final Mac getInstance(String algorithm, String provider) throws NoSuchAlgorithmException, NoSuchProviderException
Mac
object for the specified MAC algorithm
from the specified provider.
algorithm
- the standard name of the requested MAC algorithm.
See Appendix A in the
Java Cryptography Extension Reference Guide for information
about standard algorithm names.provider
- the name of the provider.
Mac
object.
NoSuchAlgorithmException
- if the specified algorithm is not
available in the default provider package or any of the other
provider packages that were searched.
NoSuchProviderException
- if the specified provider has not been
configured.
IllegalArgumentException
- if the provider
is null.public static final Mac getInstance(String algorithm, Provider provider) throws NoSuchAlgorithmException, NoSuchProviderException
Mac
object for the specified MAC algorithm
from the specified provider.
Note: the provider
doesn't have to be registered.
algorithm
- the standard name of the requested MAC algorithm.
See Appendix A in the
Java Cryptography Extension Reference Guide for information
about standard algorithm names.provider
- the provider.
Mac
object.
NoSuchAlgorithmException
- if the specified algorithm is not
available in the default provider package or any of the other
provider packages that were searched.
IllegalArgumentException
- if the provider
is null.
NoSuchProviderException
public final Provider getProvider()
Mac
object.
Mac
object.public final int getMacLength()
public final void init(Key key) throws InvalidKeyException
Mac
object with the given key.
key
- the key.
InvalidKeyException
- if the given key is inappropriate for
initializing this MAC.public final void init(Key key, AlgorithmParameterSpec params) throws InvalidKeyException, InvalidAlgorithmParameterException
Mac
object with the given key and
algorithm parameters.
key
- the key.params
- the algorithm parameters.
InvalidKeyException
- if the given key is inappropriate for
initializing this MAC.
InvalidAlgorithmParameterException
- if the given algorithm
parameters are inappropriate for this MAC.public final void update(byte input) throws IllegalStateException
input
- the input byte to be processed.
IllegalStateException
- if this Mac
has not been
initialized.public final void update(byte[] input) throws IllegalStateException
input
- the array of bytes to be processed.
IllegalStateException
- if this Mac
has not been
initialized.
NullPointerException
- if output
is null.public final void update(byte[] input, int offset, int len) throws IllegalStateException
len
bytes in input
,
starting at offset
inclusive.
input
- the input buffer.offset
- the offset in input
where the input starts.len
- the number of bytes to process.
IllegalStateException
- if this Mac
has not been
initialized.
NullPointerException
- if input
is null.public final void update(ByteBuffer input)
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.
input
- the ByteBuffer
IllegalStateException
- if this Mac
has not been
initialized or if input<\code> is null.
public final byte[] doFinal() throws IllegalStateException
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)
.
IllegalStateException
- if this Mac has not been initialized.public final void doFinal(byte[] output, int outOffset) throws ShortBufferException, IllegalStateException
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.
output
- the buffer where the MAC result is stored.outOffset
- the offset in output
where the MAC is
stored
ShortBufferException
- if the given output buffer is too small
to hold the result.
IllegalStateException
- if this Mac
has not been
initialized.
NullPointerException
- if output
is null.public final byte[] doFinal(byte[] input) throws IllegalStateException
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)
.
input
- data in bytes.
IllegalStateException
- if this Mac
has not been
initialized.public final void reset()
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)
.
public final Object clone() throws CloneNotSupportedException
clone
in class Object
CloneNotSupportedException
- if this is called on a delegate that
does not support Cloneable
.Clonable
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