Java example source code file (KeyPairGenerator.java)
The KeyPairGenerator.java Java example source code/*
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package java.security;
import java.util.*;
import java.security.spec.AlgorithmParameterSpec;
import java.security.Provider.Service;
import sun.security.jca.*;
import sun.security.jca.GetInstance.Instance;
/**
* The KeyPairGenerator class is used to generate pairs of
* public and private keys. Key pair generators are constructed using the
* {@code getInstance} factory methods (static methods that
* return instances of a given class).
*
* <p>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.
*
* <p>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:
*
* <ul>
* <li>Algorithm-Independent Initialization
* <p>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 <i>DSA algorithm, the keysize
* corresponds to the length of the modulus).
* There is an
* {@link #initialize(int, java.security.SecureRandom) initialize}
* method in this KeyPairGenerator class that takes these two universally
* shared types of arguments. There is also one that takes just a
* {@code keysize} argument, and uses the {@code SecureRandom}
* implementation of the highest-priority installed provider as the source
* of randomness. (If none of the installed providers supply an implementation
* of {@code SecureRandom}, a system-provided source of randomness is
* used.)
*
* <p>Since no other parameters are specified when you call the above
* algorithm-independent {@code 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.
*
* <p>If the algorithm is the DSA algorithm, and the keysize (modulus
* size) is 512, 768, or 1024, then the <i>Sun provider uses a set of
* precomputed values for the {@code p}, {@code q}, and
* {@code g} parameters. If the modulus size is not one of the above
* values, the <i>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.
*
* <li>Algorithm-Specific Initialization
* <p>For situations where a set of algorithm-specific parameters already
* exists (e.g., so-called <i>community parameters in DSA), there are two
* {@link #initialize(java.security.spec.AlgorithmParameterSpec)
* initialize} methods that have an {@code AlgorithmParameterSpec}
* argument. One also has a {@code SecureRandom} argument, while the
* the other uses the {@code SecureRandom}
* implementation of the highest-priority installed provider as the source
* of randomness. (If none of the installed providers supply an implementation
* of {@code SecureRandom}, a system-provided source of randomness is
* used.)
* </ul>
*
* <p>In case the client does not explicitly initialize the KeyPairGenerator
* (via a call to an {@code initialize} method), each provider must
* supply (and document) a default initialization.
* For example, the <i>Sun provider uses a default modulus size (keysize)
* of 1024 bits.
*
* <p>Note that this class is abstract and extends from
* {@code KeyPairGeneratorSpi} for historical reasons.
* Application developers should only take notice of the methods defined in
* this {@code 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.
*
* <p> Every implementation of the Java platform is required to support the
* following standard {@code KeyPairGenerator} algorithms and keysizes in
* parentheses:
* <ul>
* <li>{@code DiffieHellman} (1024)
* <li>{@code DSA} (1024)
* <li>{@code RSA} (1024, 2048)
* </ul>
* These algorithms are described in the <a href=
* "{@docRoot}/../technotes/guides/security/StandardNames.html#KeyPairGenerator">
* KeyPairGenerator section</a> of the
* Java Cryptography Architecture Standard Algorithm Name Documentation.
* Consult the release documentation for your implementation to see if any
* other algorithms are supported.
*
* @author Benjamin Renaud
*
* @see java.security.spec.AlgorithmParameterSpec
*/
public abstract class KeyPairGenerator extends KeyPairGeneratorSpi {
private final String algorithm;
// The provider
Provider provider;
/**
* Creates a KeyPairGenerator object for the specified algorithm.
*
* @param algorithm the standard string name of the algorithm.
* See the KeyPairGenerator section in the <a href=
* "{@docRoot}/../technotes/guides/security/StandardNames.html#KeyPairGenerator">
* Java Cryptography Architecture Standard Algorithm Name Documentation</a>
* for information about standard algorithm names.
*/
protected KeyPairGenerator(String algorithm) {
this.algorithm = algorithm;
}
/**
* Returns the standard name of the algorithm for this key pair generator.
* See the KeyPairGenerator section in the <a href=
* "{@docRoot}/../technotes/guides/security/StandardNames.html#KeyPairGenerator">
* Java Cryptography Architecture Standard Algorithm Name Documentation</a>
* for information about standard algorithm names.
*
* @return the standard string name of the algorithm.
*/
public String getAlgorithm() {
return this.algorithm;
}
private static KeyPairGenerator getInstance(Instance instance,
String algorithm) {
KeyPairGenerator kpg;
if (instance.impl instanceof KeyPairGenerator) {
kpg = (KeyPairGenerator)instance.impl;
} else {
KeyPairGeneratorSpi spi = (KeyPairGeneratorSpi)instance.impl;
kpg = new Delegate(spi, algorithm);
}
kpg.provider = instance.provider;
return kpg;
}
/**
* Returns a KeyPairGenerator object that generates public/private
* key pairs for the specified algorithm.
*
* <p> 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.
*
* <p> Note that the list of registered providers may be retrieved via
* the {@link Security#getProviders() Security.getProviders()} method.
*
* @param algorithm the standard string name of the algorithm.
* See the KeyPairGenerator section in the <a href=
* "{@docRoot}/../technotes/guides/security/StandardNames.html#KeyPairGenerator">
* Java Cryptography Architecture Standard Algorithm Name Documentation</a>
* for information about standard algorithm names.
*
* @return the new KeyPairGenerator object.
*
* @exception NoSuchAlgorithmException if no Provider supports a
* KeyPairGeneratorSpi implementation for the
* specified algorithm.
*
* @see Provider
*/
public static KeyPairGenerator getInstance(String algorithm)
throws NoSuchAlgorithmException {
List<Service> list =
GetInstance.getServices("KeyPairGenerator", algorithm);
Iterator<Service> t = list.iterator();
if (t.hasNext() == false) {
throw new NoSuchAlgorithmException
(algorithm + " KeyPairGenerator not available");
}
// find a working Spi or KeyPairGenerator subclass
NoSuchAlgorithmException failure = null;
do {
Service s = t.next();
try {
Instance instance =
GetInstance.getInstance(s, KeyPairGeneratorSpi.class);
if (instance.impl instanceof KeyPairGenerator) {
return getInstance(instance, algorithm);
} else {
return new Delegate(instance, t, algorithm);
}
} catch (NoSuchAlgorithmException e) {
if (failure == null) {
failure = e;
}
}
} while (t.hasNext());
throw failure;
}
/**
* Returns a KeyPairGenerator object that generates public/private
* key pairs for the specified algorithm.
*
* <p> 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.
*
* <p> Note that the list of registered providers may be retrieved via
* the {@link Security#getProviders() Security.getProviders()} method.
*
* @param algorithm the standard string name of the algorithm.
* See the KeyPairGenerator section in the <a href=
* "{@docRoot}/../technotes/guides/security/StandardNames.html#KeyPairGenerator">
* Java Cryptography Architecture Standard Algorithm Name Documentation</a>
* for information about standard algorithm names.
*
* @param provider the string name of the provider.
*
* @return the new KeyPairGenerator object.
*
* @exception NoSuchAlgorithmException if a KeyPairGeneratorSpi
* implementation for the specified algorithm is not
* available from the specified provider.
*
* @exception NoSuchProviderException if the specified provider is not
* registered in the security provider list.
*
* @exception IllegalArgumentException if the provider name is null
* or empty.
*
* @see Provider
*/
public static KeyPairGenerator getInstance(String algorithm,
String provider)
throws NoSuchAlgorithmException, NoSuchProviderException {
Instance instance = GetInstance.getInstance("KeyPairGenerator",
KeyPairGeneratorSpi.class, algorithm, provider);
return getInstance(instance, algorithm);
}
/**
* Returns a KeyPairGenerator object that generates public/private
* key pairs for the specified algorithm.
*
* <p> 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.
*
* @param algorithm the standard string name of the algorithm.
* See the KeyPairGenerator section in the <a href=
* "{@docRoot}/../technotes/guides/security/StandardNames.html#KeyPairGenerator">
* Java Cryptography Architecture Standard Algorithm Name Documentation</a>
* for information about standard algorithm names.
*
* @param provider the provider.
*
* @return the new KeyPairGenerator object.
*
* @exception NoSuchAlgorithmException if a KeyPairGeneratorSpi
* implementation for the specified algorithm is not available
* from the specified Provider object.
*
* @exception IllegalArgumentException if the specified provider is null.
*
* @see Provider
*
* @since 1.4
*/
public static KeyPairGenerator getInstance(String algorithm,
Provider provider) throws NoSuchAlgorithmException {
Instance instance = GetInstance.getInstance("KeyPairGenerator",
KeyPairGeneratorSpi.class, algorithm, provider);
return getInstance(instance, algorithm);
}
/**
* Returns the provider of this key pair generator object.
*
* @return the provider of this key pair generator object
*/
public final Provider getProvider() {
disableFailover();
return this.provider;
}
void disableFailover() {
// empty, overridden in Delegate
}
/**
* Initializes the key pair generator for a certain keysize using
* a default parameter set and the {@code SecureRandom}
* implementation of the highest-priority installed provider as the source
* of randomness.
* (If none of the installed providers supply an implementation of
* {@code SecureRandom}, a system-provided source of randomness is
* used.)
*
* @param keysize the keysize. This is an
* algorithm-specific metric, such as modulus length, specified in
* number of bits.
*
* @exception InvalidParameterException if the {@code keysize} is not
* supported by this KeyPairGenerator object.
*/
public void initialize(int keysize) {
initialize(keysize, JCAUtil.getSecureRandom());
}
/**
* Initializes the key pair generator for a certain keysize with
* the given source of randomness (and a default parameter set).
*
* @param keysize the keysize. This is an
* algorithm-specific metric, such as modulus length, specified in
* number of bits.
* @param random the source of randomness.
*
* @exception InvalidParameterException if the {@code keysize} is not
* supported by this KeyPairGenerator object.
*
* @since 1.2
*/
public void initialize(int keysize, SecureRandom random) {
// This does nothing, because either
// 1. the implementation object returned by getInstance() is an
// instance of KeyPairGenerator which has its own
// initialize(keysize, random) method, so the application would
// be calling that method directly, or
// 2. the implementation returned by getInstance() is an instance
// of Delegate, in which case initialize(keysize, random) is
// overridden to call the corresponding SPI method.
// (This is a special case, because the API and SPI method have the
// same name.)
}
/**
* Initializes the key pair generator using the specified parameter
* set and the {@code SecureRandom}
* implementation of the highest-priority installed provider as the source
* of randomness.
* (If none of the installed providers supply an implementation of
* {@code SecureRandom}, a system-provided source of randomness is
* used.).
*
* <p>This concrete method has been added to this previously-defined
* abstract class.
* This method calls the KeyPairGeneratorSpi
* {@link KeyPairGeneratorSpi#initialize(
* java.security.spec.AlgorithmParameterSpec,
* java.security.SecureRandom) initialize} method,
* passing it {@code 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 {@code initialize} method always throws an
* UnsupportedOperationException if it is not overridden by the provider.
*
* @param params the parameter set used to generate the keys.
*
* @exception InvalidAlgorithmParameterException if the given parameters
* are inappropriate for this key pair generator.
*
* @since 1.2
*/
public void initialize(AlgorithmParameterSpec params)
throws InvalidAlgorithmParameterException {
initialize(params, JCAUtil.getSecureRandom());
}
/**
* Initializes the key pair generator with the given parameter
* set and source of randomness.
*
* <p>This concrete method has been added to this previously-defined
* abstract class.
* This method calls the KeyPairGeneratorSpi {@link
* KeyPairGeneratorSpi#initialize(
* java.security.spec.AlgorithmParameterSpec,
* java.security.SecureRandom) initialize} method,
* passing it {@code params} and {@code random}.
* That {@code initialize}
* method always throws an
* UnsupportedOperationException if it is not overridden by the provider.
*
* @param params the parameter set used to generate the keys.
* @param random the source of randomness.
*
* @exception InvalidAlgorithmParameterException if the given parameters
* are inappropriate for this key pair generator.
*
* @since 1.2
*/
public void initialize(AlgorithmParameterSpec params,
SecureRandom random)
throws InvalidAlgorithmParameterException
{
// This does nothing, because either
// 1. the implementation object returned by getInstance() is an
// instance of KeyPairGenerator which has its own
// initialize(params, random) method, so the application would
// be calling that method directly, or
// 2. the implementation returned by getInstance() is an instance
// of Delegate, in which case initialize(params, random) is
// overridden to call the corresponding SPI method.
// (This is a special case, because the API and SPI method have the
// same name.)
}
/**
* Generates a key pair.
*
* <p>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.
*
* <p>This will generate a new key pair every time it is called.
*
* <p>This method is functionally equivalent to
* {@link #generateKeyPair() generateKeyPair}.
*
* @return the generated key pair
*
* @since 1.2
*/
public final KeyPair genKeyPair() {
return generateKeyPair();
}
/**
* Generates a key pair.
*
* <p>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.
*
* <p>This will generate a new key pair every time it is called.
*
* <p>This method is functionally equivalent to
* {@link #genKeyPair() genKeyPair}.
*
* @return the generated key pair
*/
public KeyPair generateKeyPair() {
// This does nothing (except returning null), because either:
//
// 1. the implementation object returned by getInstance() is an
// instance of KeyPairGenerator which has its own implementation
// of generateKeyPair (overriding this one), so the application
// would be calling that method directly, or
//
// 2. the implementation returned by getInstance() is an instance
// of Delegate, in which case generateKeyPair is
// overridden to invoke the corresponding SPI method.
//
// (This is a special case, because in JDK 1.1.x the generateKeyPair
// method was used both as an API and a SPI method.)
return null;
}
/*
* The following class allows providers to extend from KeyPairGeneratorSpi
* rather than from KeyPairGenerator. It represents a KeyPairGenerator
* with an encapsulated, provider-supplied SPI object (of type
* KeyPairGeneratorSpi).
* If the provider implementation is an instance of KeyPairGeneratorSpi,
* the getInstance() methods above return an instance of this class, with
* the SPI object encapsulated.
*
* Note: All SPI methods from the original KeyPairGenerator class have been
* moved up the hierarchy into a new class (KeyPairGeneratorSpi), which has
* been interposed in the hierarchy between the API (KeyPairGenerator)
* and its original parent (Object).
*/
//
// error failover notes:
//
// . we failover if the implementation throws an error during init
// by retrying the init on other providers
//
// . we also failover if the init succeeded but the subsequent call
// to generateKeyPair() fails. In order for this to work, we need
// to remember the parameters to the last successful call to init
// and initialize() the next spi using them.
//
// . although not specified, KeyPairGenerators could be thread safe,
// so we make sure we do not interfere with that
//
// . failover is not available, if:
// . getInstance(algorithm, provider) was used
// . a provider extends KeyPairGenerator rather than
// KeyPairGeneratorSpi (JDK 1.1 style)
// . once getProvider() is called
//
private static final class Delegate extends KeyPairGenerator {
// The provider implementation (delegate)
private volatile KeyPairGeneratorSpi spi;
private final Object lock = new Object();
private Iterator<Service> serviceIterator;
private final static int I_NONE = 1;
private final static int I_SIZE = 2;
private final static int I_PARAMS = 3;
private int initType;
private int initKeySize;
private AlgorithmParameterSpec initParams;
private SecureRandom initRandom;
// constructor
Delegate(KeyPairGeneratorSpi spi, String algorithm) {
super(algorithm);
this.spi = spi;
}
Delegate(Instance instance, Iterator<Service> serviceIterator,
String algorithm) {
super(algorithm);
spi = (KeyPairGeneratorSpi)instance.impl;
provider = instance.provider;
this.serviceIterator = serviceIterator;
initType = I_NONE;
}
/**
* Update the active spi of this class and return the next
* implementation for failover. If no more implemenations are
* available, this method returns null. However, the active spi of
* this class is never set to null.
*/
private KeyPairGeneratorSpi nextSpi(KeyPairGeneratorSpi oldSpi,
boolean reinit) {
synchronized (lock) {
// somebody else did a failover concurrently
// try that spi now
if ((oldSpi != null) && (oldSpi != spi)) {
return spi;
}
if (serviceIterator == null) {
return null;
}
while (serviceIterator.hasNext()) {
Service s = serviceIterator.next();
try {
Object inst = s.newInstance(null);
// ignore non-spis
if (inst instanceof KeyPairGeneratorSpi == false) {
continue;
}
if (inst instanceof KeyPairGenerator) {
continue;
}
KeyPairGeneratorSpi spi = (KeyPairGeneratorSpi)inst;
if (reinit) {
if (initType == I_SIZE) {
spi.initialize(initKeySize, initRandom);
} else if (initType == I_PARAMS) {
spi.initialize(initParams, initRandom);
} else if (initType != I_NONE) {
throw new AssertionError
("KeyPairGenerator initType: " + initType);
}
}
provider = s.getProvider();
this.spi = spi;
return spi;
} catch (Exception e) {
// ignore
}
}
disableFailover();
return null;
}
}
void disableFailover() {
serviceIterator = null;
initType = 0;
initParams = null;
initRandom = null;
}
// engine method
public void initialize(int keysize, SecureRandom random) {
if (serviceIterator == null) {
spi.initialize(keysize, random);
return;
}
RuntimeException failure = null;
KeyPairGeneratorSpi mySpi = spi;
do {
try {
mySpi.initialize(keysize, random);
initType = I_SIZE;
initKeySize = keysize;
initParams = null;
initRandom = random;
return;
} catch (RuntimeException e) {
if (failure == null) {
failure = e;
}
mySpi = nextSpi(mySpi, false);
}
} while (mySpi != null);
throw failure;
}
// engine method
public void initialize(AlgorithmParameterSpec params,
SecureRandom random) throws InvalidAlgorithmParameterException {
if (serviceIterator == null) {
spi.initialize(params, random);
return;
}
Exception failure = null;
KeyPairGeneratorSpi mySpi = spi;
do {
try {
mySpi.initialize(params, random);
initType = I_PARAMS;
initKeySize = 0;
initParams = params;
initRandom = random;
return;
} catch (Exception e) {
if (failure == null) {
failure = e;
}
mySpi = nextSpi(mySpi, false);
}
} while (mySpi != null);
if (failure instanceof RuntimeException) {
throw (RuntimeException)failure;
}
// must be an InvalidAlgorithmParameterException
throw (InvalidAlgorithmParameterException)failure;
}
// engine method
public KeyPair generateKeyPair() {
if (serviceIterator == null) {
return spi.generateKeyPair();
}
RuntimeException failure = null;
KeyPairGeneratorSpi mySpi = spi;
do {
try {
return mySpi.generateKeyPair();
} catch (RuntimeException e) {
if (failure == null) {
failure = e;
}
mySpi = nextSpi(mySpi, true);
}
} while (mySpi != null);
throw failure;
}
}
}
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