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java.lang.Objectjavax.crypto.Mac
public class Mac
This class implements a "message authentication code" (MAC), a method to ensure the integrity of data transmitted between two parties who share a common secret key.
The best way to describe a MAC is as a keyed one-way hash function, which looks like:
D = MAC(K, M)
where K is the key, M is the message,
and D is the resulting digest. One party will usually
send the concatenation M || D to the other party, who
will then verify D by computing D' in a
similar fashion. If D == D', then the message is assumed
to be authentic.
| Constructor Summary | |
|---|---|
protected |
Mac(MacSpi macSpi,
Provider provider,
String algorithm)
Creates a new Mac instance. |
| Method Summary | |
|---|---|
Object |
clone()
Clone this instance, if the underlying implementation supports it. |
byte[] |
doFinal()
Finishes the computation of a MAC and returns the digest. |
byte[] |
doFinal(byte[] input)
Finishes the computation of a MAC with a final byte array (or computes a MAC over those bytes only) and returns the digest. |
void |
doFinal(byte[] output,
int outOffset)
Finishes the computation of a MAC and places the result into the given array. |
String |
getAlgorithm()
Returns the name of this MAC algorithm. |
static Mac |
getInstance(String algorithm)
Create an instance of the named algorithm from the first provider with an appropriate implementation. |
static Mac |
getInstance(String algorithm,
Provider provider)
Create an instance of the named algorithm from a provider. |
static Mac |
getInstance(String algorithm,
String provider)
Create an instance of the named algorithm from the named provider. |
int |
getMacLength()
Get the size of the MAC. |
Provider |
getProvider()
Get the provider of the underlying implementation. |
void |
init(Key key)
Initialize this MAC with a key and no parameters. |
void |
init(Key key,
AlgorithmParameterSpec params)
Initialize this MAC with a key and parameters. |
void |
reset()
Reset this instance. |
void |
update(byte input)
Update the computation with a single byte. |
void |
update(byte[] input)
Update the computation with a byte array. |
void |
update(byte[] input,
int offset,
int length)
Update the computation with a portion of a byte array. |
void |
update(ByteBuffer buffer)
Update this MAC with the remaining bytes in the given buffer |
| Methods inherited from class java.lang.Object |
|---|
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
| Constructor Detail |
|---|
protected Mac(MacSpi macSpi,
Provider provider,
String algorithm)
macSpi - The underlying MAC implementation.provider - The provider of this implementation.algorithm - The name of this MAC algorithm.| Method Detail |
|---|
public static final Mac getInstance(String algorithm)
throws NoSuchAlgorithmException
algorithm - The name of the algorithm.
NoSuchAlgorithmException - If no implementation of the named
algorithm is installed.
IllegalArgumentException - if algorithm is
null or is an empty string.
public static final Mac getInstance(String algorithm,
String provider)
throws NoSuchAlgorithmException,
NoSuchProviderException
algorithm - The name of the algorithm.provider - The name of the provider.
NoSuchAlgorithmException - If the named provider has no
implementation of the algorithm.
NoSuchProviderException - If the named provider does not exist.
IllegalArgumentException - if either algorithm or
provider is null, or if
algorithm is an empty string.
public static final Mac getInstance(String algorithm,
Provider provider)
throws NoSuchAlgorithmException
algorithm - The name of the algorithm.provider - The provider.
NoSuchAlgorithmException - If the provider has no implementation of
the algorithm.
IllegalArgumentException - if either algorithm or
provider is null, or if
algorithm is an empty string.
public final byte[] doFinal()
throws IllegalStateException
After this method succeeds, it may be used again as just after a
call to init, and can compute another MAC using the
same key and parameters.
IllegalStateException - If this instnace has not
been initialized.
public final byte[] doFinal(byte[] input)
throws IllegalStateException
After this method succeeds, it may be used again as just after a
call to init, and can compute another MAC using the
same key and parameters.
input - The bytes to add.
IllegalStateException - If this instnace has not
been initialized.
public final void doFinal(byte[] output,
int outOffset)
throws IllegalStateException,
ShortBufferException
After this method succeeds, it may be used again as just after a
call to init, and can compute another MAC using the
same key and parameters.
output - The destination for the result.outOffset - The index in the output array to start.
IllegalStateException - If this instnace has not
been initialized.
ShortBufferException - If output is
not large enough to hold the result.public final String getAlgorithm()
public final int getMacLength()
doFinal() and doFinal(byte[]), and the minimum
number of bytes that must be available in the byte array passed to
doFinal(byte[],int).
public final Provider getProvider()
public final void init(Key key)
throws InvalidKeyException
key - The key to initialize this instance with.
InvalidKeyException - If the key is
unacceptable.
public final void init(Key key,
AlgorithmParameterSpec params)
throws InvalidAlgorithmParameterException,
InvalidKeyException
key - The key to initialize this instance with.params - The algorithm-specific parameters.
InvalidAlgorithmParameterException - If the
algorithm parameters are unacceptable.
InvalidKeyException - If the key is
unacceptable.public final void reset()
public final void update(byte input)
throws IllegalStateException
input - The next byte.
IllegalStateException - If this instance has not
been initialized.
public final void update(byte[] input)
throws IllegalStateException
input - The next bytes.
IllegalStateException - If this instance has not
been initialized.
public final void update(byte[] input,
int offset,
int length)
throws IllegalStateException
input - The next bytes.offset - The index in input to start.length - The number of bytes to update.
IllegalStateException - If this instance has not
been initialized.public final void update(ByteBuffer buffer)
buffer - The input buffer.
public final Object clone()
throws CloneNotSupportedException
clone in class ObjectCloneNotSupportedException - If the underlying
implementation is not cloneable.Cloneable
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