KeyPairGenerator JDK 1.6)

Description

publicabstract abstract class KeyPairGenerator

The KeyPairGenerator class is used to generate pairs of public and private keys.

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.

There are two ways to generate a key pair: in an algorithm-independent manner, and in an algorithm-specific manner. The only difference between the two is the initialization of the object:

Algorithm-Independent Initialization
All key pair generators share the concepts of a keysize and a source of randomness. The keysize is interpreted differently for different algorithms (e.g., in the case of the DSA algorithm, the keysize corresponds to the length of the modulus). There is an initialize method in this KeyPairGenerator class that takes these two universally shared types of arguments. There is also one that takes just a keysize argument, and uses 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.)
Since no other parameters are specified when you call the above algorithm-independent initialize 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.
If the algorithm is the DSA algorithm, and the keysize (modulus size) is 512, 768, or 1024, then the Sun provider uses a set of precomputed values for the p, q, and g parameters. If the modulus size is not one of the above values, the Sun provider creates a new set of parameters. Other providers might have precomputed parameter sets for more than just the three modulus sizes mentioned above. Still others might not have a list of precomputed parameters at all and instead always create new parameter sets.
Algorithm-Specific Initialization
For situations where a set of algorithm-specific parameters already exists (e.g., so-called community parameters in DSA), there are two initialize methods that have an AlgorithmParameterSpec argument. One also has a SecureRandom argument, while the the other uses 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.)

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.

See also: AlgorithmParameterSpec

Methods

Hide/Show inherited methods

pack-private void disableFailover ()

public KeyPair generateKeyPair () [Specified in KeyPairGeneratorSpi]

Generates a key pair.

publicfinal KeyPair genKeyPair ()

Generates a key pair.

public String getAlgorithm ()

Returns the standard name of the algorithm for this key pair generator.

publicstatic KeyPairGenerator getInstance (String algorithm) throws NoSuchAlgorithmException

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

publicstatic KeyPairGenerator getInstance (String algorithm, Provider provider) throws NoSuchAlgorithmException

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

publicstatic KeyPairGenerator getInstance (String algorithm, String provider) throws NoSuchAlgorithmException NoSuchProviderException

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

publicfinal Provider getProvider ()

Returns the provider of this key pair generator object.

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.

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

public void initialize (AlgorithmParameterSpec params, SecureRandom random) throws InvalidAlgorithmParameterException [Overrides KeyPairGeneratorSpi]

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

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.

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.

public void initialize (int keysize, SecureRandom random) [Specified in KeyPairGeneratorSpi]

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

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