JavaTM 2 Platform
Std. Ed. v1.4.2

javax.crypto
Class KeyGenerator

java.lang.Object
  extended byjavax.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 initialization of the object:

In case the client does not explicitly initialize the KeyGenerator (via a call to an init method), each provider must supply (and document) a default initialization.

Since:
1.4
See Also:
SecretKey

Constructor Summary
protected KeyGenerator(KeyGeneratorSpi keyGenSpi, Provider provider, String algorithm)
          Creates a KeyGenerator object.
 
Method Summary
 SecretKey generateKey()
          Generates a secret key.
 String getAlgorithm()
          Returns the algorithm name of this KeyGenerator object.
static KeyGenerator getInstance(String algorithm)
          Generates a KeyGenerator object for the specified algorithm.
static KeyGenerator getInstance(String algorithm, Provider provider)
          Generates a KeyGenerator object for the specified key algorithm from the specified provider.
static KeyGenerator getInstance(String algorithm, String provider)
          Generates a KeyGenerator object for the specified key algorithm from the specified provider.
 Provider getProvider()
          Returns the provider of this KeyGenerator object.
 void init(AlgorithmParameterSpec params)
          Initializes this key generator with the specified parameter set.
 void init(AlgorithmParameterSpec params, SecureRandom random)
          Initializes this key generator with the specified parameter set and a user-provided source of randomness.
 void init(int keysize)
          Initializes this key generator for a certain keysize.
 void init(int keysize, SecureRandom random)
          Initializes this key generator for a certain keysize, using a user-provided source of randomness.
 void init(SecureRandom random)
          Initializes this key generator.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

KeyGenerator

protected KeyGenerator(KeyGeneratorSpi keyGenSpi,
                       Provider provider,
                       String algorithm)
Creates a KeyGenerator object.

Parameters:
keyGenSpi - the delegate
provider - the provider
algorithm - the algorithm
Method Detail

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 final 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 Reference Guide 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 final 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 Reference Guide for information about standard algorithm names.
provider - the name of the provider
Returns:
the new KeyGenerator object
Throws:
NoSuchAlgorithmException - if a key generator for the specified algorithm is not available from the specified provider.
NoSuchProviderException - if the specified provider has not been configured.
IllegalArgumentException - if the provider is null.

getInstance

public static final KeyGenerator getInstance(String algorithm,
                                             Provider provider)
                                      throws NoSuchAlgorithmException
Generates a KeyGenerator object for the specified key algorithm from the specified provider. Note: the provider doesn't have to be registered.

Parameters:
algorithm - the standard name of the requested key algorithm. See Appendix A in the Java Cryptography Extension Reference Guide for information about standard algorithm names.
provider - the provider
Returns:
the new KeyGenerator object
Throws:
NoSuchAlgorithmException - if a key generator for the specified algorithm is not available from the specified provider.
IllegalArgumentException - if the provider is null.

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)
Initializes this key generator.

Parameters:
random - the source of randomness for this generator

init

public final void init(AlgorithmParameterSpec params)
                throws InvalidAlgorithmParameterException
Initializes this key generator with the specified parameter set.

If this key generator requires any random bytes, it will get them using the SecureRandom implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness will be used.)

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
Initializes this 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 keysize)
Initializes this key generator for a certain keysize.

If this key generator requires any random bytes, it will get them using the SecureRandom implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness will be used.)

Parameters:
keysize - the keysize. This is an algorithm-specific metric, specified in number of bits.
Throws:
InvalidParameterException - if the keysize is wrong or not supported.

init

public final void init(int keysize,
                       SecureRandom random)
Initializes this key generator for a certain keysize, using a user-provided source of randomness.

Parameters:
keysize - the keysize. This is an algorithm-specific metric, specified in number of bits.
random - the source of randomness for this key generator
Throws:
InvalidParameterException - if the keysize is wrong or not supported.

generateKey

public final SecretKey generateKey()
Generates a secret key.

Returns:
the new key

JavaTM 2 Platform
Std. Ed. v1.4.2

Submit a bug or feature
For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

Copyright 2003 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.


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