Cloneable
public class Mac extends Object implements Cloneable
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., SHA256 or SHA384, in combination with a secret shared key. HMAC is specified in RFC 2104.
Every implementation of the Java platform is required to support the following standard Mac
algorithms:
HmacSHA1
HmacSHA256
Modifier | Constructor | Description |
---|---|---|
protected |
Creates a MAC object. |
Modifier and Type | Method | Description |
---|---|---|
final Object |
clone() |
Returns a clone if the provider implementation is cloneable. |
final byte[] |
doFinal() |
Finishes the MAC operation. |
final byte[] |
doFinal |
Processes the given array of bytes and finishes the MAC operation. |
final void |
doFinal |
Finishes the MAC operation. |
final String |
getAlgorithm() |
Returns the algorithm name of this Mac object. |
static final Mac |
getInstance |
Returns a Mac object that implements the specified MAC algorithm. |
static final Mac |
getInstance |
Returns a Mac object that implements the specified MAC algorithm. |
static final Mac |
getInstance |
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 |
Initializes this Mac object with the given key. |
final void |
init |
Initializes this Mac object with the given key and algorithm parameters. |
final void |
reset() |
Resets this Mac object. |
final void |
update |
Processes the given byte. |
final void |
update |
Processes the given array of bytes. |
final void |
update |
Processes the first len bytes in input , starting at offset inclusive. |
final void |
update |
Processes input.remaining() bytes in the ByteBuffer input , starting at input.position() . |
protected Mac(MacSpi macSpi, Provider provider, String algorithm)
macSpi
- the delegateprovider
- the provideralgorithm
- the algorithmpublic 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. 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.
jdk.security.provider.preferred
Security
property to determine the preferred provider order for the specified algorithm. This may be different from the order of providers returned by Security.getProviders()
.algorithm
- the standard name of the requested MAC algorithm. See the Mac section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.Mac
objectNoSuchAlgorithmException
- if no Provider
supports a MacSpi
implementation for the specified algorithmNullPointerException
- if algorithm
is null
public static final Mac getInstance(String algorithm, String provider) throws NoSuchAlgorithmException, NoSuchProviderException
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.
algorithm
- the standard name of the requested MAC algorithm. See the Mac section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.provider
- the name of the provider.Mac
objectIllegalArgumentException
- if the provider
is null
or emptyNoSuchAlgorithmException
- if a MacSpi
implementation for the specified algorithm is not available from the specified providerNoSuchProviderException
- if the specified provider is not registered in the security provider listNullPointerException
- if algorithm
is null
public static final Mac getInstance(String algorithm, Provider provider) throws NoSuchAlgorithmException
Mac
object that implements the specified MAC algorithm. A new Mac
object encapsulating the MacSpi
implementation from the specified provider is returned. Note that the specified provider does not have to be registered in the provider list.
algorithm
- the standard name of the requested MAC algorithm. See the Mac section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.provider
- the provider.Mac
objectIllegalArgumentException
- if the provider
is null
NoSuchAlgorithmException
- if a MacSpi
implementation for the specified algorithm is not available from the specified Provider
objectNullPointerException
- if algorithm
is null
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.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.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 ByteBufferIllegalStateException
- if this Mac
has not been initialized.IllegalArgumentException
- if input
is nullpublic 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 storedoutOffset
- the offset in output
where the MAC is storedShortBufferException
- if the given output buffer is too small to hold the resultIllegalStateException
- if this Mac
has not been initialized.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 bytesIllegalStateException
- if this Mac
has not been initialized.public final void reset()
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)
.
public final Object clone() throws CloneNotSupportedException
clone
in class Object
CloneNotSupportedException
- if this is called on a delegate that does not support Cloneable
.
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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/javax/crypto/Mac.html