- java.lang.Object
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- javax.crypto.Mac
 
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- All Implemented Interfaces:
- Cloneable
 
 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., 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 Macalgorithms:- HmacMD5
- HmacSHA1
- HmacSHA256
 - Since:
- 1.4
 
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Method SummaryAll Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description Objectclone()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.voiddoFinal(byte[] output, int outOffset)Finishes the MAC operation.StringgetAlgorithm()Returns the algorithm name of thisMacobject.static MacgetInstance(String algorithm)Returns aMacobject that implements the specified MAC algorithm.static MacgetInstance(String algorithm, String provider)Returns aMacobject that implements the specified MAC algorithm.static MacgetInstance(String algorithm, Provider provider)Returns aMacobject that implements the specified MAC algorithm.intgetMacLength()Returns the length of the MAC in bytes.ProvidergetProvider()Returns the provider of thisMacobject.voidinit(Key key)Initializes thisMacobject with the given key.voidinit(Key key, AlgorithmParameterSpec params)Initializes thisMacobject with the given key and algorithm parameters.voidreset()Resets thisMacobject.voidupdate(byte input)Processes the given byte.voidupdate(byte[] input)Processes the given array of bytes.voidupdate(byte[] input, int offset, int len)Processes the firstlenbytes ininput, starting atoffsetinclusive.voidupdate(ByteBuffer input)Processesinput.remaining()bytes in the ByteBufferinput, starting atinput.position().
 
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Method Detail- 
getAlgorithmpublic final String getAlgorithm() Returns the algorithm name of thisMacobject.This is the same name that was specified in one of the getInstancecalls that created thisMacobject.- Returns:
- the algorithm name of this Macobject.
 
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getInstancepublic static final Mac getInstance(String algorithm) throws NoSuchAlgorithmException Returns aMacobject 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.- Implementation Note:
- The JDK Reference Implementation additionally uses the
 jdk.security.provider.preferredSecurityproperty to determine the preferred provider order for the specified algorithm. This may be different than the order of providers returned bySecurity.getProviders().
- Parameters:
- 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.
- Returns:
- the new Macobject
- Throws:
- NoSuchAlgorithmException- if no- Providersupports a- MacSpiimplementation for the specified algorithm
- NullPointerException- if- algorithmis- null
- See Also:
- Provider
 
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getInstancepublic static final Mac getInstance(String algorithm, String provider) throws NoSuchAlgorithmException, NoSuchProviderException Returns aMacobject 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 Security Standard Algorithm Names Specification for information about standard algorithm names.
- provider- the name of the provider.
- Returns:
- the new Macobject
- Throws:
- IllegalArgumentException- if the- provideris- nullor empty
- NoSuchAlgorithmException- if a- MacSpiimplementation for the specified algorithm is not available from the specified provider
- NoSuchProviderException- if the specified provider is not registered in the security provider list
- NullPointerException- if- algorithmis- null
- See Also:
- Provider
 
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getInstancepublic static final Mac getInstance(String algorithm, Provider provider) throws NoSuchAlgorithmException Returns aMacobject 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 Security Standard Algorithm Names Specification for information about standard algorithm names.
- provider- the provider.
- Returns:
- the new Macobject
- Throws:
- IllegalArgumentException- if the- provideris- null
- NoSuchAlgorithmException- if a- MacSpiimplementation for the specified algorithm is not available from the specified- Providerobject
- NullPointerException- if- algorithmis- null
- See Also:
- Provider
 
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getProviderpublic final Provider getProvider() Returns the provider of thisMacobject.- Returns:
- the provider of this Macobject.
 
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getMacLengthpublic final int getMacLength() Returns the length of the MAC in bytes.- Returns:
- the MAC length in bytes.
 
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initpublic final void init(Key key) throws InvalidKeyException Initializes thisMacobject with the given key.- Parameters:
- key- the key.
- Throws:
- InvalidKeyException- if the given key is inappropriate for initializing this MAC.
 
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initpublic final void init(Key key, AlgorithmParameterSpec params) throws InvalidKeyException, InvalidAlgorithmParameterException Initializes thisMacobject 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.
 
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updatepublic final void update(byte input) throws IllegalStateExceptionProcesses the given byte.- Parameters:
- input- the input byte to be processed.
- Throws:
- IllegalStateException- if this- Machas not been initialized.
 
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updatepublic 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- Machas not been initialized.
 
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updatepublic final void update(byte[] input, int offset, int len) throws IllegalStateExceptionProcesses the firstlenbytes ininput, starting atoffsetinclusive.- Parameters:
- input- the input buffer.
- offset- the offset in- inputwhere the input starts.
- len- the number of bytes to process.
- Throws:
- IllegalStateException- if this- Machas not been initialized.
 
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updatepublic final void update(ByteBuffer input) Processesinput.remaining()bytes in the ByteBufferinput, starting atinput.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- Machas not been initialized.
- Since:
- 1.5
 
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doFinalpublic final byte[] doFinal() throws IllegalStateExceptionFinishes the MAC operation.A call to this method resets this Macobject to the state it was in when previously initialized via a call toinit(Key)orinit(Key, AlgorithmParameterSpec). That is, the object is reset and available to generate another MAC from the same key, if desired, via new calls toupdateanddoFinal. (In order to reuse thisMacobject with a different key, it must be reinitialized via a call toinit(Key)orinit(Key, AlgorithmParameterSpec).- Returns:
- the MAC result.
- Throws:
- IllegalStateException- if this- Machas not been initialized.
 
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doFinalpublic final void doFinal(byte[] output, int outOffset) throws ShortBufferException, IllegalStateExceptionFinishes the MAC operation.A call to this method resets this Macobject to the state it was in when previously initialized via a call toinit(Key)orinit(Key, AlgorithmParameterSpec). That is, the object is reset and available to generate another MAC from the same key, if desired, via new calls toupdateanddoFinal. (In order to reuse thisMacobject with a different key, it must be reinitialized via a call toinit(Key)orinit(Key, AlgorithmParameterSpec).The MAC result is stored in output, starting atoutOffsetinclusive.- Parameters:
- output- the buffer where the MAC result is stored
- outOffset- the offset in- outputwhere the MAC is stored
- Throws:
- ShortBufferException- if the given output buffer is too small to hold the result
- IllegalStateException- if this- Machas not been initialized.
 
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doFinalpublic final byte[] doFinal(byte[] input) throws IllegalStateExceptionProcesses the given array of bytes and finishes the MAC operation.A call to this method resets this Macobject to the state it was in when previously initialized via a call toinit(Key)orinit(Key, AlgorithmParameterSpec). That is, the object is reset and available to generate another MAC from the same key, if desired, via new calls toupdateanddoFinal. (In order to reuse thisMacobject with a different key, it must be reinitialized via a call toinit(Key)orinit(Key, AlgorithmParameterSpec).- Parameters:
- input- data in bytes
- Returns:
- the MAC result.
- Throws:
- IllegalStateException- if this- Machas not been initialized.
 
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resetpublic final void reset() Resets thisMacobject.A call to this method resets this Macobject to the state it was in when previously initialized via a call toinit(Key)orinit(Key, AlgorithmParameterSpec). That is, the object is reset and available to generate another MAC from the same key, if desired, via new calls toupdateanddoFinal. (In order to reuse thisMacobject with a different key, it must be reinitialized via a call toinit(Key)orinit(Key, AlgorithmParameterSpec).
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clonepublic final Object clone() throws CloneNotSupportedException Returns a clone if the provider implementation is cloneable.- Overrides:
- clonein class- Object
- Returns:
- 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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