java.lang.Object | +--java.security.KeyPairGeneratorSpi | +--java.security.KeyPairGenerator
Untamed: 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:
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.
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.
java.security.spec.AlgorithmParameterSpecprotected
KeyPairGenerator(String algorithm)
String
getAlgorithm()
static KeyPairGenerator
getInstance(String algorithm)
static KeyPairGenerator
getInstance(String algorithm,
Provider provider)
static KeyPairGenerator
getInstance(String algorithm,
String provider)
void
initialize(AlgorithmParameterSpec params)
SecureRandom
implementation of the highest-priority installed provider as the source
of randomness.
void
initialize(AlgorithmParameterSpec params,
SecureRandom random)
void
initialize(int keysize)
SecureRandom
implementation of the highest-priority installed provider as the source
of randomness.
void
initialize(int keysize,
SecureRandom random)
private String algorithm
private Provider provider
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.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.
NoSuchAlgorithmExceptionpublic 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.
NoSuchAlgorithmException
NoSuchProviderExceptionProviderpublic static KeyPairGenerator getInstance(String algorithm, Provider provider) throws NoSuchAlgorithmException
provider doesn't have to be registered.
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 provider.
NoSuchAlgorithmExceptionProviderpublic final Provider getProvider()
public void initialize(int keysize)
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.)
keysize - the keysize. This is an
algorithm-specific metric, such as modulus length, specified in
number of bits.public void initialize(int keysize, SecureRandom random)
initialize in class KeyPairGeneratorSpikeysize - the keysize. This is an
algorithm-specific metric, such as modulus length, specified in
number of bits.random - the source of randomness.public void initialize(AlgorithmParameterSpec params) throws InvalidAlgorithmParameterException
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(java.security.spec.AlgorithmParameterSpec,
java.security.SecureRandom) 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.
params - the parameter set used to generate the keys.
InvalidAlgorithmParameterExceptionpublic void initialize(AlgorithmParameterSpec params, SecureRandom random) throws InvalidAlgorithmParameterException
This concrete method has been added to this previously-defined
abstract class.
This method calls the KeyPairGeneratorSpi initialize(java.security.spec.AlgorithmParameterSpec,
java.security.SecureRandom) initialize method,
passing it params and random.
That initialize
method always throws an
UnsupportedOperationException if it is not overridden by the provider.
initialize in class KeyPairGeneratorSpiparams - the parameter set used to generate the keys.random - the source of randomness.
InvalidAlgorithmParameterExceptionpublic final KeyPair genKeyPair()
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.
public KeyPair generateKeyPair()
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.
generateKeyPair in class KeyPairGeneratorSpi