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java.lang.Object | +----java.security.KeyPairGeneratorSpi | +----java.security.KeyPairGenerator
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:
All key pair 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
initialize
method in this KeyPairGenerator 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.
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 strength (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.
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
source of randomness is system-provided for the other.
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 (strength)
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, and ignore all the methods in
the superclass.
Constructor Summary | |
KeyPairGenerator(String algorithm)
|
Method Summary | |
KeyPair | genKeyPair()
|
String | getAlgorithm()
|
static KeyPairGenerator | getInstance(String algorithm)
|
static KeyPairGenerator | getInstance(String algorithm,
String provider)
|
Provider | getProvider()
|
void | initialize(int strength)
|
void | initialize(AlgorithmParameterSpec params)
|
Methods inherited from class java.security.KeyPairGeneratorSpi |
generateKeyPair, initialize, initialize |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
protected KeyPairGenerator(String algorithm)
algorithm
- the standard string name of the algorithm.
See Appendix A in the
Java Cryptography Architecture API Specification & Reference
for information about standard algorithm names.
Method Detail |
public String getAlgorithm()
public static KeyPairGenerator getInstance(String algorithm) throws NoSuchAlgorithmException
algorithm
- the standard string name of the algorithm.
See Appendix A in the
Java Cryptography Architecture API Specification & Reference
for information about standard algorithm names.
public static KeyPairGenerator getInstance(String algorithm, String provider) throws NoSuchAlgorithmException, NoSuchProviderException
algorithm
- the standard string name of the algorithm.
See Appendix A in the
Java Cryptography Architecture API Specification & Reference
for information about standard algorithm names.
provider
- the string name of the provider.
public final Provider getProvider()
public void initialize(int strength)
strength
- the strength of the key. This is an
algorithm-specific metric, such as modulus length, specified in
number of bits.
public void initialize(AlgorithmParameterSpec params) throws InvalidAlgorithmParameterException
This concrete method has been added to this previously-defined
abstract class.
This method calls initialize,
passing it params
and a
system-provided source of randomness. That initialize
method always throws an
UnsupportedOperationException if it is not overridden by the provider.
params
- the parameter set used to generate the keys.
public final KeyPair genKeyPair()
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