- All Implemented Interfaces:
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:
HmacSHA1HmacSHA256
- Since:
- 1.4
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionfinal Objectclone()Returns a clone if the provider implementation is cloneable.final byte[]doFinal()Finishes the MAC operation.final byte[]doFinal(byte[] input) Processes the given array of bytes and finishes the MAC operation.final voiddoFinal(byte[] output, int outOffset) Finishes the MAC operation.final StringReturns the algorithm name of thisMacobject.static final MacgetInstance(String algorithm) Returns aMacobject that implements the specified MAC algorithm.static final MacgetInstance(String algorithm, String provider) Returns aMacobject that implements the specified MAC algorithm.static final MacgetInstance(String algorithm, Provider provider) Returns aMacobject that implements the specified MAC algorithm.final intReturns the length of the MAC in bytes.final ProviderReturns the provider of thisMacobject.final voidInitializes thisMacobject with the given key.final voidinit(Key key, AlgorithmParameterSpec params) Initializes thisMacobject with the given key and algorithm parameters.final voidreset()Resets thisMacobject.final voidupdate(byte input) Processes the given byte.final voidupdate(byte[] input) Processes the given array of bytes.final voidupdate(byte[] input, int offset, int len) Processes the firstlenbytes ininput, starting atoffsetinclusive.final voidupdate(ByteBuffer input) Processesinput.remaining()bytes in the ByteBufferinput, starting atinput.position().
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Constructor Details
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Mac
Creates a MAC object.- Parameters:
macSpi- the delegateprovider- the provideralgorithm- the algorithm
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Method Details
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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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getInstance
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
Macobject encapsulating theMacSpiimplementation 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 from 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 noProvidersupports aMacSpiimplementation for the specified algorithmNullPointerException- ifalgorithmisnull- See Also:
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getInstance
public static final Mac getInstance(String algorithm, String provider) throws NoSuchAlgorithmException, NoSuchProviderException Returns aMacobject that implements the specified MAC algorithm.A new
Macobject encapsulating theMacSpiimplementation 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 theproviderisnullor emptyNoSuchAlgorithmException- if aMacSpiimplementation for the specified algorithm is not available from the specified providerNoSuchProviderException- if the specified provider is not registered in the security provider listNullPointerException- ifalgorithmisnull- See Also:
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getInstance
public static final Mac getInstance(String algorithm, Provider provider) throws NoSuchAlgorithmException Returns aMacobject that implements the specified MAC algorithm.A new
Macobject encapsulating theMacSpiimplementation from the specified provider is returned. Note that the specified provider 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 theproviderisnullNoSuchAlgorithmException- if aMacSpiimplementation for the specified algorithm is not available from the specifiedProviderobjectNullPointerException- ifalgorithmisnull- See Also:
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getProvider
Returns the provider of thisMacobject.- Returns:
- the provider of this
Macobject.
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getMacLength
public final int getMacLength()Returns the length of the MAC in bytes.- Returns:
- the MAC length in bytes.
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init
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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init
public 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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update
Processes the given byte.- Parameters:
input- the input byte to be processed.- Throws:
IllegalStateException- if thisMachas not been initialized.
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update
Processes the given array of bytes.- Parameters:
input- the array of bytes to be processed.- Throws:
IllegalStateException- if thisMachas not been initialized.
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update
Processes the firstlenbytes ininput, starting atoffsetinclusive.- Parameters:
input- the input buffer.offset- the offset ininputwhere the input starts.len- the number of bytes to process.- Throws:
IllegalStateException- if thisMachas not been initialized.
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update
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 thisMachas not been initialized.IllegalArgumentException- ifinputis null- Since:
- 1.5
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doFinal
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).- Returns:
- the MAC result.
- Throws:
IllegalStateException- if thisMachas not been initialized.
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doFinal
public final void doFinal(byte[] output, int outOffset) throws ShortBufferException, IllegalStateException 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).The MAC result is stored in
output, starting atoutOffsetinclusive.- Parameters:
output- the buffer where the MAC result is storedoutOffset- the offset inoutputwhere the MAC is stored- Throws:
ShortBufferException- if the given output buffer is too small to hold the resultIllegalStateException- if thisMachas not been initialized.
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doFinal
Processes 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 thisMachas not been initialized.
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reset
public 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). -
clone
Returns a clone if the provider implementation is cloneable.- Overrides:
clonein classObject- Returns:
- a clone if the provider implementation is cloneable.
- Throws:
CloneNotSupportedException- if this is called on a delegate that does not supportCloneable.- See Also:
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