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java.lang.Object | +--javax.crypto.Mac
This class provides the functionality of a "message authentication code" (MAC).
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., MD5 or SHA-1, in combination with a secret shared key. HMAC is specified in RFC 2104.
Constructor Summary | |
protected |
Mac(MacSpi macSpi,
Provider provider,
String algorithm)
Creates a MAC object. |
Method Summary | |
Object |
clone()
Returns a clone if the 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 standard name of the MAC algorithm. |
static Mac |
getInstance(String algorithm)
Generates an Mac object that implements the specified MAC algorithm. |
static Mac |
getInstance(String algorithm,
String provider)
Generates an Mac object for the specified MAC algorithm from the specified provider. |
int |
getMacLength()
Returns the length of the MAC in bytes. |
Provider |
getProvider()
Returns the provider of this Mac object. |
void |
init(Key key)
Initializes the MAC with the given (secret) key. |
void |
init(Key key,
AlgorithmParameterSpec params)
Initializes the MAC with the given (secret) 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. |
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 delegateprovider
- the provideralgorithm
- the algorithmMethod Detail |
public final String getAlgorithm()
This is the same name that was specified in one of the getInstance calls that created this Mac object.
public static final Mac getInstance(String algorithm) throws NoSuchAlgorithmException
algorithm
- the standard name of the requested MAC
algorithm. See Appendix A in the Java Cryptography
Extension API Specification & Reference for information
about standard algorithm names.public static final Mac getInstance(String algorithm, String provider) throws NoSuchAlgorithmException, NoSuchProviderException
algorithm
- the standard name of the requested MAC
algorithm. See Appendix A in the Java Cryptography
Extension API Specification & Reference for information
about standard algorithm names.provider
- the providerpublic final Provider getProvider()
public final int getMacLength()
public final void init(Key key) throws InvalidKeyException
key
- the (secret) key.public final void init(Key key, AlgorithmParameterSpec params) throws InvalidKeyException, InvalidAlgorithmParameterException
key
- the (secret) key.params
- the algorithm parameters.public final void update(byte input) throws IllegalStateException
input
- the input byte to be processed.public final void update(byte[] input) throws IllegalStateException
input
- the array of bytes to be processed.public final void update(byte[] input, int offset, int len) throws IllegalStateException
input
- the input buffer.offset
- the offset in input where the input starts.len
- the number of bytes to process.public final byte[] doFinal() throws IllegalStateException
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).
public final void doFinal(byte[] output, int outOffset) throws ShortBufferException, IllegalStateException
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).
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 storedpublic final byte[] doFinal(byte[] input) throws IllegalStateException
Processes 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).
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).
public Object clone() throws CloneNotSupportedException
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