- java.lang.Object
- javax.crypto.Mac
- All Implemented Interfaces:Cloneable
public class Mac extends Object implements CloneableThis 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., 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:
- HmacMD5
- HmacSHA1
- HmacSHA256
These algorithms are described in the Mac section of the Java Cryptography Architecture Standard Algorithm Name Documentation. Consult the release documentation for your implementation to see if any other algorithms are supported.
Since:1.4
Constructor Summary
ConstructorsModifierConstructor and Description protected Mac(MacSpi macSpi, Provider provider, String algorithm) Creates a MAC object.
Method Summary
MethodsModifier and TypeMethod and Description 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) Returns a Mac object that implements the specified MAC algorithm.
static Mac getInstance(String algorithm, Provider provider) Returns a Mac object that implements the specified MAC algorithm.
static Mac getInstance(String algorithm, String provider) Returns a Mac object that implements the specified MAC algorithm.
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
Constructor Detail
Mac
protected Mac(MacSpi macSpi, Provider provider, String algorithm)Creates a MAC object.
Parameters:macSpi - the delegateprovider - the provideralgorithm - the algorithm
Method Detail
getAlgorithm
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: the algorithm name of this Mac object.
getInstance
public static final Mac getInstance(String algorithm) throws NoSuchAlgorithmExceptionReturns 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 - 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:the new Mac object.Throws:NoSuchAlgorithmException - if no Provider supports a MacSpi implementation for the specified algorithm.See Also:Provider
getInstance
public static final Mac getInstance(String algorithm, String provider) throws NoSuchAlgorithmException, NoSuchProviderExceptionReturns 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 - 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 - the name of the provider.Returns: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
public static final Mac getInstance(String algorithm, Provider provider) throws NoSuchAlgorithmExceptionReturns 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 - 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 - the provider.Returns: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
getProvider
public final Provider getProvider()Returns the provider of this Mac object.
Returns:the provider of this Mac object.
getMacLength
public final int getMacLength()Returns the length of the MAC in bytes.
Returns:the MAC length in bytes.
init
public final void init(Key key) throws InvalidKeyExceptionInitializes this Mac object with the given key.
Parameters:key - the key.Throws:InvalidKeyException - if the given key is inappropriate for initializing this MAC.
init
public final void init(Key key, AlgorithmParameterSpec params) throws InvalidKeyException, InvalidAlgorithmParameterExceptionInitializes this Mac object with the given key and algorithm parameters.
Parameters:key - the key.params - 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.
update
public final void update(byte input) throws IllegalStateExceptionProcesses the given byte.
Parameters:input - the input byte to be processed.Throws:IllegalStateException - if this Mac has not been initialized.
update
public final void update(byte[] input) throws IllegalStateExceptionProcesses the given array of bytes.
Parameters:input - the array of bytes to be processed.Throws:IllegalStateException - if this Mac has not been initialized.
update
public final void update(byte[] input, int offset, int len) throws IllegalStateExceptionProcesses the first len bytes in input, starting at offset inclusive.
update
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 - the ByteBuffer Throws:IllegalStateException - if this Mac has not been initialized.Since:1.5
doFinal
public final byte[] doFinal() throws IllegalStateExceptionFinishes 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:the MAC result.Throws:IllegalStateException - if this Mac has not been initialized.
doFinal
public final void doFinal(byte[] output, int outOffset) throws ShortBufferException, IllegalStateExceptionFinishes 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 - the buffer where the MAC result is storedoutOffset - the offset in output where the MAC is storedThrows:ShortBufferException - if the given output buffer is too small to hold the resultIllegalStateException - if this Mac has not been initialized.
doFinal
public final byte[] doFinal(byte[] input) throws IllegalStateExceptionProcesses 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 bytesReturns:the MAC result.Throws:IllegalStateException - if this Mac has not been initialized.
reset
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).
clone
public final Object clone() throws CloneNotSupportedExceptionReturns a clone if the provider implementation is cloneable.
Overrides:clone in class ObjectReturns:a clone if the provider implementation is cloneable.Throws:CloneNotSupportedException - if this is called on a delegate that does not support Cloneable.See Also:Cloneable
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