KeyFactory JDK 1.6)

Description

public class KeyFactory

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.

Key factories are bi-directional. 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);

See also: Key PublicKey PrivateKey KeySpec DSAPublicKeySpec X509EncodedKeySpec

Methods

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publicfinal PrivateKey generatePrivate (KeySpec keySpec) throws InvalidKeySpecException

Generates a private key object from the provided key specification (key material).

publicfinal PublicKey generatePublic (KeySpec keySpec) throws InvalidKeySpecException

Generates a public key object from the provided key specification (key material).

publicfinal String getAlgorithm ()

Gets the name of the algorithm associated with this KeyFactory.

publicstatic KeyFactory getInstance (String algorithm) throws NoSuchAlgorithmException

Returns a KeyFactory object that converts public/private keys of the specified algorithm.

publicstatic KeyFactory getInstance (String algorithm, Provider provider) throws NoSuchAlgorithmException

Returns a KeyFactory object that converts public/private keys of the specified algorithm.

publicstatic KeyFactory getInstance (String algorithm, String provider) throws NoSuchAlgorithmException NoSuchProviderException

Returns a KeyFactory object that converts public/private keys of the specified algorithm.

publicfinal T getKeySpec (Key key, Class< T> keySpec) throws InvalidKeySpecException

Returns a specification (key material) of the given key object.

Returns a specification (key material) of the given key object.
keySpec identifies the specification class in which
the key material should be returned. It could, for example, be
DSAPublicKeySpec.class, to indicate that the
key material should be returned in an instance of the
DSAPublicKeySpec class.
Returns: the underlying key specification (key material) in an instance of the requested specification class.
Parameters:
- key - the key.
- keySpec - the specification class in which the key material should be returned.
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).

publicfinal Provider getProvider ()

Returns the provider of this key factory object.

publicfinal Key translateKey (Key key) throws InvalidKeyException

Translates a key object, whose provider may be unknown or potentially untrusted, into a corresponding key object of this key factory.