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Class javax.crypto.KeyGenerator
java.lang.Object
|
+----javax.crypto.KeyGenerator
- public class KeyGenerator
- extends Object
This class provides the functionality of a (symmetric) key generator.
Key generators are constructed using one of the getInstance class methods
of this class.
KeyGenerator objects are reusable, i.e., after a key has been generated, the
same KeyGenerator object can be re-used to generate further keys.
There are two ways to generate a key: in an algorithm-independent manner,
and in an algorithm-specific manner. The only difference between the two is
the initialisation of the object:
Algorithm-Independent Initialisation
All key generators share the concepts of a "strength" and a source of
randomness. The measure of strength is universally shared by all
algorithms, though it is interpreted differently for different algorithms.
There is an init method in this KeyGenerator class that takes these two
universally shared types of arguments. There is also one that takes just a
strength argument, and uses a system-provided source of randomness,
and one that takes just a source of randomness.
Since no other parameters are specified when you call the above
algorithm-independent init methods, it is up to the provider what to do
about the algorithm-specific parameters (if any) to be associated with
each of the keys.
Algorithm-Specific Initialisation
For situations where a set of algorithm-specific parameters already
exists, there are two init methods that have an
AlgorithmParameterSpec argument. One also has a SecureRandom
argument, while the source of randomness is system-provided for the
other.
In case the client does not explicitly initialise the KeyGenerator (via a
call to an init method), each provider must supply (and document) a default
initialisation.
- See Also:
- SecretKey
-
ident
-
-
KeyGenerator(KeyGeneratorSpi, Provider, String)
- Creates a KeyGenerator object using the given provider,
KeyGeneratorSpi and for the specified algorithm.
-
generateKey()
- Generates a secret key.
-
getAlgorithm()
- Returns the algorithm name of this KeyGenerator object.
-
getInstance(String)
- Generates a KeyGenerator object for the specified algorithm.
-
getInstance(String, String)
- Generates a KeyGenerator object for the specified key algorithm from
the specified provider.
-
getProvider()
- Returns the provider of this KeyGenerator object.
-
init(AlgorithmParameterSpec)
- Initialises the key generator with the specified parameter set,
using a system-provided source of randomness.
-
init(AlgorithmParameterSpec, SecureRandom)
- Initialises the key generator with the specified parameter set
and a user-provided source of randomness.
-
init(int)
- Initialises this key generator for a certain strength, using a
system-provided source of randomness.
-
init(int, SecureRandom)
- Initialises this key generator for a certain strength, using a
user-provided source of randomness.
-
init(SecureRandom)
- Initialises the key generator.
ident
public static final String ident
KeyGenerator
protected KeyGenerator(KeyGeneratorSpi spi,
Provider provider,
String algorithm)
- Creates a KeyGenerator object using the given provider,
KeyGeneratorSpi and for the specified algorithm.
- Parameters:
- spi - the KeyGeneratorSpi to use
- provider - the provider to use
- algorithm - the standard name of the key algorithm. See
Appendix A in the Java Cryptography Architecture API
Specification & Reference for information about standard
algorithm names.
getAlgorithm
public final String getAlgorithm()
- Returns the algorithm name of this KeyGenerator object.
This is the same name that was specified in one of the getInstance
calls that created this KeyGenerator object.
- Returns:
- the algorithm name of this KeyGenerator object.
getInstance
public static KeyGenerator getInstance(String algorithm) throws NoSuchAlgorithmException
- Generates a KeyGenerator object for the specified algorithm. If the
default provider package provides an implementation of the requested
key generator, an instance of KeyGenerator containing that
implementation is returned. If the requested key generator is not
available in the default provider package, other provider packages are
searched.
- Parameters:
- algorithm - the standard name of the requested key algorithm.
See Appendix A in the Java Cryptography Extension API
Specification & Reference for information about standard
algorithm names.
- Returns:
- the new KeyGenerator object
- Throws: NoSuchAlgorithmException
- if a key generator for
the specified algorithm is not available in the default provider
package or any of the other provider packages that were searched.
getInstance
public static KeyGenerator getInstance(String algorithm,
String provider) throws NoSuchAlgorithmException, NoSuchProviderException
- Generates a KeyGenerator object for the specified key algorithm from
the specified provider.
- Parameters:
- algorithm - the standard name of the requested key algorithm.
See Appendix A in the Java Cryptography Extension API
Specification & Reference for information about standard
algorithm names.
- provider - the name of the provider
- Throws: NoSuchAlgorithmException
- if a key generator for the
requested algorithm is not available.
- Throws: NoSuchProviderException
- if the requested provider is
not available
- See Also:
- Provider
getProvider
public final Provider getProvider()
- Returns the provider of this KeyGenerator object.
- Returns:
- the provider of this KeyGenerator object
init
public final void init(SecureRandom random)
- Initialises the key generator.
- Parameters:
- random - the source of randomness for this generator.
init
public final void init(AlgorithmParameterSpec params) throws InvalidAlgorithmParameterException
- Initialises the key generator with the specified parameter set,
using a system-provided source of randomness.
- Parameters:
- params - the key generation parameters
- Throws: InvalidAlgorithmParameterException
- if the given
parameters are inappropriate for this key generator.
init
public final void init(AlgorithmParameterSpec params,
SecureRandom random) throws InvalidAlgorithmParameterException
- Initialises the key generator with the specified parameter set
and a user-provided source of randomness.
- Parameters:
- params - the key generation parameters
- random - the source of randomness for this key generator
- Throws: InvalidAlgorithmParameterException
- if params is
inappropriate for this key generator.
init
public final void init(int strength)
- Initialises this key generator for a certain strength, using a
system-provided source of randomness.
- Parameters:
- strength - the strength of the key. This is an algorithm-specific
metric specified in number of bits.
init
public final void init(int strength,
SecureRandom random)
- Initialises this key generator for a certain strength, using a
user-provided source of randomness.
- Parameters:
- strength - the strength of the key. This is an algorithm-specific
metric specified in number of bits.
- random - the source of randomness for this key generator
generateKey
public SecretKey generateKey()
- Generates a secret key.
- Returns:
- the new key
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