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., MD5 or SHA-1, in combination with a secret shared key. HMAC is specified in RFC 2104.
Android provides the following Mac
algorithms:
Algorithm | Supported API Levels |
---|---|
DESMAC | 1-8 |
DESMAC/CFB8 | 1-8 |
DESedeMAC | 1-8 |
DESedeMAC/CFB8 | 1-8 |
DESedeMAC64 | 1-8 |
DESwithISO9797 | 1-8 |
HmacMD5 | 1+ |
HmacSHA1 | 1+ |
HmacSHA224 | 1-8,22+ |
HmacSHA256 | 1+ |
HmacSHA384 | 1+ |
HmacSHA512 | 1+ |
ISO9797ALG3MAC | 1-8 |
PBEwithHmacSHA | 1+ |
PBEwithHmacSHA1 | 1+ |
PBEwithHmacSHA224 | 26+ |
PBEwithHmacSHA256 | 26+ |
PBEwithHmacSHA384 | 26+ |
PBEwithHmacSHA512 | 26+ |
Protected Constructor Summary
Public Method Summary
final Object |
clone()
Returns a clone if the provider implementation is cloneable.
|
final byte[] |
doFinal(byte[] input)
Processes the given array of bytes and finishes the MAC operation.
|
final void |
doFinal(byte[] output, int outOffset)
Finishes the MAC operation.
|
final byte[] |
doFinal()
Finishes the MAC operation.
|
final String |
getAlgorithm()
Returns the algorithm name of this
Mac object. |
final static Mac | |
final static Mac |
getInstance(String algorithm, String provider)
Returns a
Mac object that implements the
specified MAC algorithm. |
final static Mac |
getInstance(String algorithm, Provider provider)
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(Key key, AlgorithmParameterSpec params)
Initializes this
Mac object with the given key and
algorithm parameters. |
final void | |
final void |
reset()
Resets this
Mac object. |
final void |
update(byte[] input)
Processes the given array of bytes.
|
final void |
update(byte[] input, int offset, int len)
Processes the first
len bytes in input ,
starting at offset inclusive. |
final void |
update(ByteBuffer input)
Processes
input.remaining() bytes in the ByteBuffer
input , starting at input.position() . |
final void |
update(byte input)
Processes the given byte.
|
Inherited Method Summary
Protected Constructors
Public Methods
public final Object clone ()
Returns a clone if the provider implementation is cloneable.
Returns
- a clone if the provider implementation is cloneable.
Throws
CloneNotSupportedException | if this is called on a
delegate that does not support Cloneable .
|
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public final byte[] doFinal (byte[] input)
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)
.
Parameters
input | data in bytes |
---|
Returns
- the MAC result.
Throws
IllegalStateException | if this Mac has not been
initialized.
|
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public final void doFinal (byte[] output, int outOffset)
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.
Parameters
output | the buffer where the MAC result is stored |
---|---|
outOffset | the offset in output where the MAC is
stored |
Throws
ShortBufferException | if the given output buffer is too small to hold the result |
---|---|
IllegalStateException | if this Mac has not been
initialized.
|
public final byte[] doFinal ()
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)
.
Returns
- the MAC result.
Throws
IllegalStateException | if this Mac has not been
initialized.
|
---|
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.
public static final Mac getInstance (String algorithm)
Returns 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
public static final Mac getInstance (String algorithm, String provider)
Returns 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
public static final Mac getInstance (String algorithm, Provider provider)
Returns 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
public final int getMacLength ()
Returns the length of the MAC in bytes.
Returns
- the MAC length in bytes.
public final Provider getProvider ()
Returns the provider of this Mac
object.
Returns
- the provider of this
Mac
object.
public final void init (Key key, AlgorithmParameterSpec params)
Initializes 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. |
public final void init (Key key)
Initializes this Mac
object with the given key.
Parameters
key | the key. |
---|
Throws
InvalidKeyException | if the given key is inappropriate for initializing this MAC. |
---|
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 final void update (byte[] input)
Processes the given array of bytes.
Parameters
input | the array of bytes to be processed. |
---|
Throws
IllegalStateException | if this Mac has not been
initialized.
|
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public final void update (byte[] input, int offset, int len)
Processes the first len
bytes in input
,
starting at offset
inclusive.
Parameters
input | the input buffer. |
---|---|
offset | the offset in input where the input starts. |
len | the number of bytes to process. |
Throws
IllegalStateException | if this Mac has not been
initialized.
|
---|
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. |
---|
public final void update (byte input)
Processes the given byte.
Parameters
input | the input byte to be processed. |
---|
Throws
IllegalStateException | if this Mac has not been
initialized.
|
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