public abstract class KeyPairGenerator extends KeyPairGeneratorSpi
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, 1024, or 2048, 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
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 for DSA key pairs.
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.
Every implementation of the Java platform is required to support the
following standard KeyPairGenerator
algorithms and keysizes in
parentheses:
DiffieHellman
(1024, 2048, 4096)DSA
(1024, 2048)RSA
(1024, 2048, 4096)AlgorithmParameterSpec
Modifier | Constructor | Description |
---|---|---|
protected |
KeyPairGenerator(String algorithm) |
Creates a KeyPairGenerator object for the specified algorithm.
|
Modifier and Type | Method | Description |
---|---|---|
KeyPair |
generateKeyPair() |
Generates a key pair.
|
KeyPair |
genKeyPair() |
Generates a key pair.
|
String |
getAlgorithm() |
Returns the standard name of the algorithm for this key pair generator.
|
static KeyPairGenerator |
getInstance(String algorithm) |
Returns a KeyPairGenerator object that generates public/private
key pairs for the specified algorithm.
|
static KeyPairGenerator |
getInstance(String algorithm,
String provider) |
Returns a KeyPairGenerator object that generates public/private
key pairs for the specified algorithm.
|
static KeyPairGenerator |
getInstance(String algorithm,
Provider provider) |
Returns a KeyPairGenerator object that generates public/private
key pairs for the specified algorithm.
|
Provider |
getProvider() |
Returns the provider of this key pair generator object.
|
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).
|
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.
|
protected KeyPairGenerator(String algorithm)
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.public String getAlgorithm()
public static KeyPairGenerator getInstance(String algorithm) throws NoSuchAlgorithmException
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()
method.
jdk.security.provider.preferred
Security
property to determine
the preferred provider order for the specified algorithm. This
may be different than the order of providers returned by
Security.getProviders()
.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.KeyPairGenerator
objectNoSuchAlgorithmException
- if no Provider
supports a
KeyPairGeneratorSpi
implementation for the
specified algorithmNullPointerException
- if algorithm
is null
Provider
public static KeyPairGenerator getInstance(String algorithm, String provider) throws NoSuchAlgorithmException, NoSuchProviderException
A new KeyPairGenerator object encapsulating the KeyPairGeneratorSpi implementation from the specified provider is returned. The specified provider must be registered in the security provider list.
Note that the list of registered providers may be retrieved via
the Security.getProviders()
method.
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.provider
- the string name of the provider.KeyPairGenerator
objectIllegalArgumentException
- if the provider name is null
or emptyNoSuchAlgorithmException
- if a KeyPairGeneratorSpi
implementation for the specified algorithm is not
available from the specified providerNoSuchProviderException
- if the specified provider is not
registered in the security provider listNullPointerException
- if algorithm
is null
Provider
public static KeyPairGenerator getInstance(String algorithm, Provider provider) throws NoSuchAlgorithmException
A new KeyPairGenerator object encapsulating the KeyPairGeneratorSpi implementation from the specified Provider object is returned. Note that the specified Provider object does not have to be registered in the provider list.
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.provider
- the provider.KeyPairGenerator
objectIllegalArgumentException
- if the specified provider is
null
NoSuchAlgorithmException
- if a KeyPairGeneratorSpi
implementation for the specified algorithm is not available
from the specified Provider
objectNullPointerException
- if algorithm
is null
Provider
public 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.InvalidParameterException
- if the keysize
is not
supported by this KeyPairGenerator object.public void initialize(int keysize, SecureRandom random)
initialize
in class KeyPairGeneratorSpi
keysize
- the keysize. This is an
algorithm-specific metric, such as modulus length, specified in
number of bits.random
- the source of randomness.InvalidParameterException
- if the keysize
is not
supported by this KeyPairGenerator object.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
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.InvalidAlgorithmParameterException
- if the given parameters
are inappropriate for this key pair generator.public 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
method,
passing it params
and random
.
That initialize
method always throws an
UnsupportedOperationException if it is not overridden by the provider.
initialize
in class KeyPairGeneratorSpi
params
- the parameter set used to generate the keys.random
- the source of randomness.InvalidAlgorithmParameterException
- if the given parameters
are inappropriate for this key pair generator.public 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
Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
Copyright © 1993, 2017, Oracle and/or its affiliates. 500 Oracle Parkway
Redwood Shores, CA 94065 USA. All rights reserved.
DRAFT 9-internal+0-adhoc.mlchung.jdk9-jdeps