KeyFactorySpi


1   /*
2    * @(#)KeyFactorySpi.java   1.12 04/05/05
3    *
4    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6    */
7   
8   package java.security;
9   
10  import java.security.spec.KeySpec  ;
11  import java.security.spec.InvalidKeySpecException  ;
12  
13  /**
14   * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)
15   * for the <code>KeyFactory</code> class.
16   * All the abstract methods in this class must be implemented by each 
17   * cryptographic service provider who wishes to supply the implementation
18   * of a key factory for a particular algorithm.
19   *
20   * <P> Key factories are used to convert <I>keys</I> (opaque
21   * cryptographic keys of type <code>Key</code>) into <I>key specifications</I>
22   * (transparent representations of the underlying key material), and vice
23   * versa.
24   *
25   * <P> Key factories are bi-directional. That is, they allow you to build an
26   * opaque key object from a given key specification (key material), or to
27   * retrieve the underlying key material of a key object in a suitable format.
28   *
29   * <P> Multiple compatible key specifications may exist for the same key.
30   * For example, a DSA public key may be specified using
31   * <code>DSAPublicKeySpec</code> or
32   * <code>X509EncodedKeySpec</code>. A key factory can be used to translate
33   * between compatible key specifications.
34   *
35   * <P> A provider should document all the key specifications supported by its
36   * key factory.
37   *
38   * @author Jan Luehe
39   *
40   * @version 1.12, 05/05/04
41   *
42   * @see KeyFactory
43   * @see Key
44   * @see PublicKey
45   * @see PrivateKey
46   * @see java.security.spec.KeySpec
47   * @see java.security.spec.DSAPublicKeySpec
48   * @see java.security.spec.X509EncodedKeySpec
49   *
50   * @since 1.2
51   */
52  
53  public abstract class KeyFactorySpi {
54  
55      /**
56       * Generates a public key object from the provided key
57       * specification (key material).
58       *
59       * @param keySpec the specification (key material) of the public key.
60       *
61       * @return the public key.
62       *
63       * @exception InvalidKeySpecException if the given key specification
64       * is inappropriate for this key factory to produce a public key.
65       */
66      protected abstract PublicKey   engineGeneratePublic(KeySpec   keySpec)
67          throws InvalidKeySpecException  ;
68  
69      /**
70       * Generates a private key object from the provided key
71       * specification (key material).
72       *
73       * @param keySpec the specification (key material) of the private key.
74       *
75       * @return the private key.
76       *
77       * @exception InvalidKeySpecException if the given key specification
78       * is inappropriate for this key factory to produce a private key.
79       */
80      protected abstract PrivateKey   engineGeneratePrivate(KeySpec   keySpec)
81          throws InvalidKeySpecException  ;
82  
83      /**
84       * Returns a specification (key material) of the given key
85       * object.
86       * <code>keySpec</code> identifies the specification class in which 
87       * the key material should be returned. It could, for example, be
88       * <code>DSAPublicKeySpec.class</code>, to indicate that the
89       * key material should be returned in an instance of the 
90       * <code>DSAPublicKeySpec</code> class.
91       *
92       * @param key the key.
93       *
94       * @param keySpec the specification class in which 
95       * the key material should be returned.
96       *
97       * @return the underlying key specification (key material) in an instance
98       * of the requested specification class.
99  
100      * @exception InvalidKeySpecException if the requested key specification is
101      * inappropriate for the given key, or the given key cannot be dealt with
102      * (e.g., the given key has an unrecognized format).
103      */
104     protected abstract <T extends KeySpec  >
105     T engineGetKeySpec(Key   key, Class  <T> keySpec)
106     throws InvalidKeySpecException  ;
107 
108     /**
109      * Translates a key object, whose provider may be unknown or
110      * potentially untrusted, into a corresponding key object of this key
111      * factory.
112      *
113      * @param key the key whose provider is unknown or untrusted.
114      *
115      * @return the translated key.
116      *
117      * @exception InvalidKeyException if the given key cannot be processed
118      * by this key factory.
119      */
120     protected abstract Key   engineTranslateKey(Key   key)
121     throws InvalidKeyException  ;
122 
123 }
124
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