java.security
Class KeyPairGenerator
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 GNU 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 GNU
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
GNU 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.
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() .
|
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() .
|
String | getAlgorithm() - Returns the standard name of the algorithm for this key pair generator.
|
static KeyPairGenerator | getInstance(String algorithm) - Generates a
KeyPairGenerator object that implements the
specified digest algorithm.
|
static KeyPairGenerator | getInstance(String algorithm, String provider) - Generates a
KeyPairGenerator object implementing the
specified algorithm, as supplied from the specified provider, if
such an algorithm is available from the provider.
|
static KeyPairGenerator | getInstance(String algorithm, Provider provider) - Generates a
KeyPairGenerator object implementing the specified
algorithm, as supplied from the specified provider, if such an algorithm is
available from the provider.
|
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.
This concrete method has been added to this previously-defined abstract
class.
|
clone , equals , finalize , getClass , hashCode , notify , notifyAll , toString , wait , wait , wait |
KeyPairGenerator
protected KeyPairGenerator(String algorithm)
Creates a KeyPairGenerator
object for the specified
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.
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()
.
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()
.
- generateKeyPair in interface KeyPairGeneratorSpi
getAlgorithm
public String getAlgorithm()
Returns the standard name of the algorithm for this key pair generator.
See Appendix A in the Java Cryptography Architecture API Specification
& Reference for information about standard algorithm names.
- the standard string name of the algorithm.
getInstance
public static KeyPairGenerator getInstance(String algorithm)
throws NoSuchAlgorithmException
Generates a KeyPairGenerator
object that implements the
specified digest algorithm. If the default provider package provides an
implementation of the requested digest algorithm, an instance of
KeyPairGenerator
containing that implementation is returned.
If the algorithm is not available in the default package, other packages
are searched.
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.
- the new
KeyPairGenerator
object.
getInstance
public static KeyPairGenerator getInstance(String algorithm,
String provider)
throws NoSuchAlgorithmException,
NoSuchProviderException
Generates a KeyPairGenerator
object implementing the
specified algorithm, as supplied from the specified provider, if
such an algorithm is available from the provider.
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.
- the new
KeyPairGenerator
object.
getInstance
public static KeyPairGenerator getInstance(String algorithm,
Provider provider)
throws NoSuchAlgorithmException
Generates a KeyPairGenerator
object implementing the specified
algorithm, as supplied from the specified provider, if such an algorithm is
available from the provider. Note: the 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.
- the new
KeyPairGenerator
object.
getProvider
public final Provider getProvider()
Returns the provider of this key pair generator object.
- the provider of this key pair generator object.
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.)
keysize
- the keysize. This is an algorithm-specific metric, such as
modulus length, specified in number of bits.
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).
- initialize in interface KeyPairGeneratorSpi
keysize
- the keysize. This is an algorithm-specific metric, such as
modulus length, specified in number of bits.random
- the source of randomness.
KeyPairGenerator.java --- Key Pair Generator Class
Copyright (C) 1999, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
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