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## java.security
Class KeyFactorySpi

    java.lang.Object
      java.security.KeyFactorySpi

    public abstract class KeyFactorySpi

extends Object

This class defines the Service Provider Interface (SPI) for the `KeyFactory` class. All the abstract methods in this class must be implemented by each cryptographic service provider who wishes to supply the implementation of a key factory for a particular algorithm.

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.

A provider should document all the key specifications supported by its key factory.

Since:
  1.2
See Also:
  `KeyFactory`, `Key`, `PublicKey`, `PrivateKey`, `KeySpec`, `DSAPublicKeySpec`, `X509EncodedKeySpec`

Constructor Summary
`KeyFactorySpi()`

Method Summary
`protected abstract PrivateKey` | `engineGeneratePrivate(KeySpec keySpec)` Generates a private key object from the provided key specification (key material).
`protected abstract PublicKey` | `engineGeneratePublic(KeySpec keySpec)` Generates a public key object from the provided key specification (key material).
`protected abstract
`<T extends KeySpec> T`
` | `engineGetKeySpec(Key key, Class<T> keySpec)` Returns a specification (key material) of the given key object.
`protected abstract Key` | `engineTranslateKey(Key key)` Translates a key object, whose provider may be unknown or potentially untrusted, into a corresponding key object of this key factory.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### KeyFactorySpi

    public KeyFactorySpi()

Method Detail

### engineGeneratePublic

    protected abstract PublicKey engineGeneratePublic(KeySpec keySpec)
                                               throws InvalidKeySpecException

  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.

### engineGeneratePrivate

    protected abstract PrivateKey engineGeneratePrivate(KeySpec keySpec)
                                                 throws InvalidKeySpecException

  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.

### engineGetKeySpec

    protected abstract <T extends KeySpec> T engineGetKeySpec(Key key,
                                                              Class<T> keySpec)
                                                   throws InvalidKeySpecException

  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.

  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 dealt with (e.g., the given key has an unrecognized format).

### engineTranslateKey

    protected abstract Key engineTranslateKey(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.

  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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For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

Copyright 2004 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.