java.security

Class KeyPairGenerator

java.lang.Object

java.security.KeyPairGeneratorSpi

java.security.KeyPairGenerator

public abstract class KeyPairGenerator
extends KeyPairGeneratorSpi

The KeyPairGenerator class is used to generate pairs of public and private keys. Key pair generators are constructed using the getInstance factory methods (static methods that return instances of a given class).

A Key pair generator for a particular algorithm creates a public/private key pair that can be used with this algorithm. It also associates algorithm-specific parameters with each of the generated keys.

In case the client does not explicitly initialize the KeyPairGenerator (via a call to an initialize method), each provider must supply (and document) a default initialization. For example, the Sun provider uses a default modulus size (keysize) of 1024 bits.

Note that this class is abstract and extends from KeyPairGeneratorSpi for historical reasons. Application developers should only take notice of the methods defined in this KeyPairGenerator class; all the methods in the superclass are intended for cryptographic service providers who wish to supply their own implementations of key pair generators.

Author:

Benjamin Renaud

See Also:

AlgorithmParameterSpec

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	KeyPairGenerator(String algorithm) Creates a KeyPairGenerator object for the specified algorithm.

Method Summary

Modifier and Type	Method and Description
KeyPair	generateKeyPair() Generates a key pair.
KeyPair	genKeyPair() Generates a key pair.
static KeyPairGenerator	getInstance(String algorithm) Returns a KeyPairGenerator object that generates public/private key pairs for the specified algorithm.
void	initialize(AlgorithmParameterSpec params) Initializes the key pair generator using the specified parameter set and the SecureRandom implementation of the highest-priority installed provider as the source of randomness.
void	initialize(AlgorithmParameterSpec params, SecureRandom random) Initializes the key pair generator with the given parameter set and source of randomness.
void	initialize(int keysize) Initializes the key pair generator for a certain keysize using a default parameter set and the SecureRandom implementation of the highest-priority installed provider as the source of randomness.
void	initialize(int keysize, SecureRandom random) Initializes the key pair generator for a certain keysize with the given source of randomness (and a default parameter set).

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

KeyPairGenerator

protected KeyPairGenerator(String algorithm)

Creates a KeyPairGenerator object for the specified algorithm.

Parameters:

algorithm - the standard string name of the algorithm. See the KeyPairGenerator section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.

Method Detail

getInstance

public static KeyPairGenerator getInstance(String algorithm)
                                    throws NoSuchAlgorithmException

Returns a KeyPairGenerator object that generates public/private key pairs for the specified algorithm.

This method traverses the list of registered security Providers, starting with the most preferred Provider. A new KeyPairGenerator object encapsulating the KeyPairGeneratorSpi 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() Security.getProviders()} method.

Parameters:

algorithm - the standard string name of the algorithm. See the KeyPairGenerator section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.

Returns:

the new KeyPairGenerator object.

Throws:

NoSuchAlgorithmException - if no Provider supports a KeyPairGeneratorSpi implementation for the specified algorithm.

initialize

public void initialize(int keysize)

Initializes the key pair generator for a certain keysize using a default parameter set and 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 is used.)

Parameters:

keysize - the keysize. This is an algorithm-specific metric, such as modulus length, specified in number of bits.

Throws:

InvalidParameterException - if the keysize is not supported by this KeyPairGenerator object.

initialize

public void initialize(int keysize,
                       SecureRandom random)

Initializes the key pair generator for a certain keysize with the given source of randomness (and a default parameter set).

Specified by:

initialize in class KeyPairGeneratorSpi

Parameters:

keysize - the keysize. This is an algorithm-specific metric, such as modulus length, specified in number of bits.

random - the source of randomness.

Throws:

InvalidParameterException - if the keysize is not supported by this KeyPairGenerator object.

Since:

1.2

initialize

public void initialize(AlgorithmParameterSpec params)
                throws InvalidAlgorithmParameterException

Initializes the key pair generator using the specified parameter set and 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 is used.).

This concrete method has been added to this previously-defined abstract class. This method calls the KeyPairGeneratorSpi initialize method, passing it params and a source of randomness (obtained from the highest-priority installed provider or system-provided if none of the installed providers supply one). That initialize method always throws an UnsupportedOperationException if it is not overridden by the provider.

Parameters:

params - the parameter set used to generate the keys.

Throws:

InvalidAlgorithmParameterException - if the given parameters are inappropriate for this key pair generator.

Since:

1.2

initialize

public void initialize(AlgorithmParameterSpec params,
                       SecureRandom random)
                throws InvalidAlgorithmParameterException

Initializes the key pair generator with the given parameter set and source of randomness.

This concrete method has been added to this previously-defined abstract class. This method calls the KeyPairGeneratorSpi initialize method, passing it params and random. That initialize method always throws an UnsupportedOperationException if it is not overridden by the provider.

Overrides:

initialize in class KeyPairGeneratorSpi

Parameters:

params - the parameter set used to generate the keys.

random - the source of randomness.

Throws:

InvalidAlgorithmParameterException - if the given parameters are inappropriate for this key pair generator.

Since:

1.2

genKeyPair

public final KeyPair genKeyPair()

Generates a key pair.

If this KeyPairGenerator has not been initialized explicitly, provider-specific defaults will be used for the size and other (algorithm-specific) values of the generated keys.

This will generate a new key pair every time it is called.

This method is functionally equivalent to generateKeyPair.

Returns:

the generated key pair

Since:

1.2

generateKeyPair

public KeyPair generateKeyPair()

Generates a key pair.

If this KeyPairGenerator has not been initialized explicitly, provider-specific defaults will be used for the size and other (algorithm-specific) values of the generated keys.

This will generate a new key pair every time it is called.

This method is functionally equivalent to genKeyPair.

Specified by:

generateKeyPair in class KeyPairGeneratorSpi

Returns:

the generated key pair