package javax.crypto; import java.security.Provider; import java.security.InvalidKeyException; import java.security.NoSuchAlgorithmException; import java.security.NoSuchProviderException; import java.security.spec.KeySpec; import java.security.spec.InvalidKeySpecException; /** * This class represents a factory for secret keys. * *
* Key factories are used to convert keys (opaque
* cryptographic keys of type Key
) into key specifications
* (transparent representations of the underlying key material), and vice versa.
* Secret key factories operate only on secret (symmetric) keys.
*
* Key factories are bi-directional, i.e., they allow to build an opaque * key object from a given key specification (key material), or to retrieve * the underlying key material of a key object in a suitable format. *
* Application developers should refer to their provider's documentation
* to find out which key specifications are supported by the
* generateSecret and
* getKeySpec methods.
* For example, the DES secret-key factory supplied by the "SunJCE" provider
* supports DESKeySpec
as a transparent representation of DES
* keys, and that provider's secret-key factory for Triple DES keys supports
* DESedeKeySpec
as a transparent representation of Triple DES keys.
*
* @see SecretKey
* @see javax.crypto.spec.DESKeySpec
* @see javax.crypto.spec.DESedeKeySpec
* @see javax.crypto.spec.PBEKeySpec
*/
public class SecretKeyFactory
{
SecretKeyFactorySpi keyFacSpi;
Provider provider;
String algorithm;
/**
* Creates a SecretKeyFactory object.
*
* @param keyFacSpi the delegate
* @param provider the provider
* @param algorithm the secret-key algorithm
*/
protected SecretKeyFactory(
SecretKeyFactorySpi keyFacSpi,
Provider provider,
String algorithm)
{
this.keyFacSpi = keyFacSpi;
this.provider = provider;
this.algorithm = algorithm;
}
/**
* Generates a SecretKeyFactory
object for the specified secret-key algorithm.
* If the default provider package provides an implementation of the
* requested factory, an instance of SecretKeyFactory
* containing that implementation is returned.
* If the requested factory is not available in the default provider
* package, other provider packages are searched.
*
* @param algorithm the standard name of the requested secret-key algorithm.
* See Appendix A in the Java Cryptography Extension API Specification & Reference
* for information about standard algorithm names.
* @return a SecretKeyFactory
object for the specified secret-key algorithm.
* @exception NoSuchAlgorithmException if a secret-key factory for the specified algorithm
* is not available in the default provider package or any of the other provider packages
* that were searched.
*/
public static final SecretKeyFactory getInstance(
String algorithm)
throws NoSuchAlgorithmException
{
try
{
JCEUtil.Implementation imp = JCEUtil.getImplementation("SecretKeyFactory", algorithm, (String) null);
if (imp == null)
{
throw new NoSuchAlgorithmException(algorithm + " not found");
}
SecretKeyFactory keyFact = new SecretKeyFactory(
(SecretKeyFactorySpi)imp.getEngine(), imp.getProvider(), algorithm);
return keyFact;
}
catch (NoSuchProviderException e)
{
throw new NoSuchAlgorithmException(algorithm + " not found");
}
}
/**
* Generates a SecretKeyFactory
object for the specified
* secret-key algorithm from the specified provider.
*
* @param algorithm the standard name of the requested secret-key algorithm.
* See Appendix A in the Java Cryptography Extension API Specification & Reference
* for information about standard algorithm names.
* @param provider the name of the provider.
* @return a SecretKeyFactory
object for the specified secret-key algorithm.
* @exception NoSuchAlgorithmException if a secret-key factory for the specified algorithm is not
* available from the specified provider.
* @exception NoSuchProviderException if the specified provider has not been configured.
*/
public static final SecretKeyFactory getInstance(
String algorithm,
String provider)
throws NoSuchAlgorithmException, NoSuchProviderException
{
if (provider == null)
{
throw new IllegalArgumentException("No provider specified to SecretKeyFactory.getInstance()");
}
JCEUtil.Implementation imp = JCEUtil.getImplementation("SecretKeyFactory", algorithm, provider);
if (imp == null)
{
throw new NoSuchAlgorithmException(algorithm + " not found");
}
SecretKeyFactory keyFact = new SecretKeyFactory(
(SecretKeyFactorySpi)imp.getEngine(), imp.getProvider(), algorithm);
return keyFact;
}
/**
* Generates a SecretKeyFactory
object for the specified
* secret-key algorithm from the specified provider.
*
* @param algorithm the standard name of the requested secret-key algorithm.
* See Appendix A in the Java Cryptography Extension API Specification & Reference
* for information about standard algorithm names.
* @param provider the provider.
* @return a SecretKeyFactory
object for the specified secret-key algorithm.
* @exception NoSuchAlgorithmException if a secret-key factory for the specified algorithm is not
* available from the specified provider.
*/
public static final SecretKeyFactory getInstance(
String algorithm,
Provider provider)
throws NoSuchAlgorithmException
{
if (provider == null)
{
throw new IllegalArgumentException("No provider specified to SecretKeyFactory.getInstance()");
}
JCEUtil.Implementation imp = JCEUtil.getImplementation("SecretKeyFactory", algorithm, provider);
if (imp == null)
{
throw new NoSuchAlgorithmException(algorithm + " not found");
}
SecretKeyFactory keyFact = new SecretKeyFactory(
(SecretKeyFactorySpi)imp.getEngine(), imp.getProvider(), algorithm);
return keyFact;
}
/**
* Returns the provider of this SecretKeyFactory
object.
*
* @return the provider of this SecretKeyFactory
object
*/
public final Provider getProvider()
{
return provider;
}
/**
* Returns the algorithm name of this SecretKeyFactory
object.
*
* This is the same name that was specified in one of the getInstance
calls
* that created this SecretKeyFactory
object.
*
* @return the algorithm name of this SecretKeyFactory
object.
*/
public final String getAlgorithm()
{
return algorithm;
}
/**
* Generates a SecretKey
object from the provided key specification (key material).
*
* @param keySpec the specification (key material) of the secret key
* @return the secret key
* @exception InvalidKeySpecException if the given key specification
* is inappropriate for this secret-key factory to produce a secret key.
*/
public final SecretKey generateSecret(
KeySpec keySpec)
throws InvalidKeySpecException
{
return keyFacSpi.engineGenerateSecret(keySpec);
}
/**
* Returns a specification (key material) of the given key object
* in the requested format.
*
* @param key the key
* @param keySpec the requested format in which the key material shall be
* returned
* @return the underlying key specification (key material) in the requested format
* @exception InvalidKeySpecException if the requested key specification is inappropriate for
* the given key (e.g., the algorithms associated with key
and keySpec
do
* not match, or key
references a key on a cryptographic hardware device whereas
* keySpec
is the specification of a software-based key), or the given key cannot be dealt with
* (e.g., the given key has an algorithm or format not supported by this secret-key factory).
*/
public final KeySpec getKeySpec(
SecretKey key,
Class keySpec)
throws InvalidKeySpecException
{
return keyFacSpi.engineGetKeySpec(key, keySpec);
}
/**
* Translates a key object, whose provider may be unknown or potentially
* untrusted, into a corresponding key object of this secret-key factory.
*
* @param key the key whose provider is unknown or untrusted
* @return the translated key
* @exception InvalidKeyException if the given key cannot be processed by this secret-key factory.
*/
public final SecretKey translateKey(
SecretKey key)
throws InvalidKeyException
{
return keyFacSpi.engineTranslateKey(key);
}
}