Key) into key specifications
(transparent representations of the underlying key material), and vice
versa.
Key factories are bidirectional. That is, they allow you 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.
Multiple compatible key specifications may exist for the same key.
For example, a DSA public key may be specified using
DSAPublicKeySpec or
X509EncodedKeySpec. A key factory can be used to translate
between compatible key specifications.
The following is an example of how to use a key factory in order to instantiate a DSA public key from its encoding. Assume Alice has received a digital signature from Bob. Bob also sent her his public key (in encoded format) to verify his signature. Alice then performs the following actions:
X509EncodedKeySpec bobPubKeySpec = new X509EncodedKeySpec(bobEncodedPubKey);
KeyFactory keyFactory = KeyFactory.getInstance("DSA");
PublicKey bobPubKey = keyFactory.generatePublic(bobPubKeySpec);
Signature sig = Signature.getInstance("DSA");
sig.initVerify(bobPubKey);
sig.update(data);
sig.verify(signature);
Every implementation of the Java platform is required to support the
following standard KeyFactory algorithms:
DiffieHellmanDSARSA
- Since:
- 1.2
- See Also:
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Constructor Summary
ConstructorsModifierConstructorDescriptionprotectedKeyFactory(KeyFactorySpi keyFacSpi, Provider provider, String algorithm) Creates aKeyFactoryobject. -
Method Summary
Modifier and TypeMethodDescriptionfinal PrivateKeygeneratePrivate(KeySpec keySpec) Generates a private key object from the provided key specification (key material).final PublicKeygeneratePublic(KeySpec keySpec) Generates a public key object from the provided key specification (key material).final StringGets the name of the algorithm associated with thisKeyFactory.static KeyFactorygetInstance(String algorithm) Returns aKeyFactoryobject that converts public/private keys of the specified algorithm.static KeyFactorygetInstance(String algorithm, String provider) Returns aKeyFactoryobject that converts public/private keys of the specified algorithm.static KeyFactorygetInstance(String algorithm, Provider provider) Returns aKeyFactoryobject that converts public/private keys of the specified algorithm.final <T extends KeySpec>
TgetKeySpec(Key key, Class<T> keySpec) Returns a specification (key material) of the given key object.final ProviderReturns the provider of this key factory object.final KeytranslateKey(Key key) Translates a key object, whose provider may be unknown or potentially untrusted, into a corresponding key object of this key factory.
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Constructor Details
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KeyFactory
Creates aKeyFactoryobject.- Parameters:
keyFacSpi- the delegateprovider- the provideralgorithm- the name of the algorithm to associate with thisKeyFactory
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Method Details
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getInstance
Returns aKeyFactoryobject that converts public/private keys of the specified algorithm.This method traverses the list of registered security providers, starting with the most preferred provider. A new
KeyFactoryobject encapsulating theKeyFactorySpiimplementation 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.- Implementation Note:
- The JDK Reference Implementation additionally uses the
jdk.security.provider.preferredSecurityproperty to determine the preferred provider order for the specified algorithm. This may be different from the order of providers returned bySecurity.getProviders(). - Parameters:
algorithm- the name of the requested key algorithm. See the KeyFactory section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.- Returns:
- the new
KeyFactoryobject - Throws:
NoSuchAlgorithmException- if noProvidersupports aKeyFactorySpiimplementation for the specified algorithmNullPointerException- ifalgorithmisnull- See Also:
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getInstance
public static KeyFactory getInstance(String algorithm, String provider) throws NoSuchAlgorithmException, NoSuchProviderException Returns aKeyFactoryobject that converts public/private keys of the specified algorithm.A new
KeyFactoryobject encapsulating theKeyFactorySpiimplementation 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.- Parameters:
algorithm- the name of the requested key algorithm. See the KeyFactory section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.provider- the name of the provider.- Returns:
- the new
KeyFactoryobject - Throws:
IllegalArgumentException- if the provider name isnullor emptyNoSuchAlgorithmException- if aKeyFactorySpiimplementation for the specified algorithm is not available from the specified providerNoSuchProviderException- if the specified provider is not registered in the security provider listNullPointerException- ifalgorithmisnull- See Also:
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getInstance
public static KeyFactory getInstance(String algorithm, Provider provider) throws NoSuchAlgorithmException Returns aKeyFactoryobject that converts public/private keys of the specified algorithm.A new
KeyFactoryobject encapsulating theKeyFactorySpiimplementation from the specified provider is returned. Note that the specified provider does not have to be registered in the provider list.- Parameters:
algorithm- the name of the requested key algorithm. See the KeyFactory section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.provider- the provider.- Returns:
- the new
KeyFactoryobject - Throws:
IllegalArgumentException- if the specified provider isnullNoSuchAlgorithmException- if aKeyFactorySpiimplementation for the specified algorithm is not available from the specifiedProviderobjectNullPointerException- ifalgorithmisnull- Since:
- 1.4
- See Also:
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getProvider
Returns the provider of this key factory object.- Returns:
- the provider of this key factory object
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getAlgorithm
Gets the name of the algorithm associated with thisKeyFactory.- Returns:
- the name of the algorithm associated with this
KeyFactory
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generatePublic
Generates a public key object from the provided key specification (key material).- Parameters:
keySpec- the specification (key material) of the public key.- Returns:
- the public key.
- Throws:
InvalidKeySpecException- if the given key specification is inappropriate for this key factory to produce a public key.
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generatePrivate
Generates a private key object from the provided key specification (key material).- Parameters:
keySpec- the specification (key material) of the private key.- Returns:
- the private key.
- Throws:
InvalidKeySpecException- if the given key specification is inappropriate for this key factory to produce a private key.
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getKeySpec
public final <T extends KeySpec> T getKeySpec(Key key, Class<T> keySpec) throws InvalidKeySpecException Returns a specification (key material) of the given key object.keySpecidentifies the specification class in which the key material should be returned. It could, for example, beDSAPublicKeySpec.class, to indicate that the key material should be returned in an instance of theDSAPublicKeySpecclass.- Type Parameters:
T- the type of the key specification to be returned- Parameters:
key- the key.keySpec- the specification class in which the key material should be returned.- Returns:
- the underlying key specification (key material) in an instance of the requested specification class.
- Throws:
InvalidKeySpecException- if the requested key specification is inappropriate for the given key, or the given key cannot be processed (e.g., the given key has an unrecognized algorithm or format).
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translateKey
Translates a key object, whose provider may be unknown or potentially untrusted, into a corresponding key object of this key factory.- Parameters:
key- the key whose provider is unknown or untrusted.- Returns:
- the translated key.
- Throws:
InvalidKeyException- if the given key cannot be processed by this key factory.
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