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25 
26 package java.security;
27 
28 import java.security.spec.AlgorithmParameterSpec;
29 
30 /**
31  * <p> This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)
32  * for the {@code KeyPairGenerator} class, which is used to generate
33  * pairs of public and private keys.
34  *
35  * <p> All the abstract methods in this class must be implemented by each
36  * cryptographic service provider who wishes to supply the implementation
37  * of a key pair generator for a particular algorithm.
38  *
39  * <p> In case the client does not explicitly initialize the KeyPairGenerator
40  * (via a call to an {@code initialize} method), each provider must
41  * supply (and document) a default initialization.
42  * For example, the <i>Sun</i> provider uses a default modulus size (keysize)
43  * of 1024 bits.
44  *
45  * @author Benjamin Renaud
46  *
47  *
48  * @see KeyPairGenerator
49  * @see java.security.spec.AlgorithmParameterSpec
50  */
51 
52 public abstract class KeyPairGeneratorSpi {
53 
54     /**
55      * Initializes the key pair generator for a certain keysize, using
56      * the default parameter set.
57      *
58      * @param keysize the keysize. This is an
59      * algorithm-specific metric, such as modulus length, specified in
60      * number of bits.
61      *
62      * @param random the source of randomness for this generator.
63      *
64      * @exception InvalidParameterException if the {@code keysize} is not
65      * supported by this KeyPairGeneratorSpi object.
66      */
initialize(int keysize, SecureRandom random)67     public abstract void initialize(int keysize, SecureRandom random);
68 
69     /**
70      * Initializes the key pair generator using the specified parameter
71      * set and user-provided source of randomness.
72      *
73      * <p>This concrete method has been added to this previously-defined
74      * abstract class. (For backwards compatibility, it cannot be abstract.)
75      * It may be overridden by a provider to initialize the key pair
76      * generator. Such an override
77      * is expected to throw an InvalidAlgorithmParameterException if
78      * a parameter is inappropriate for this key pair generator.
79      * If this method is not overridden, it always throws an
80      * UnsupportedOperationException.
81      *
82      * @param params the parameter set used to generate the keys.
83      *
84      * @param random the source of randomness for this generator.
85      *
86      * @exception InvalidAlgorithmParameterException if the given parameters
87      * are inappropriate for this key pair generator.
88      *
89      * @since 1.2
90      */
initialize(AlgorithmParameterSpec params, SecureRandom random)91     public void initialize(AlgorithmParameterSpec params,
92                            SecureRandom random)
93         throws InvalidAlgorithmParameterException {
94             throw new UnsupportedOperationException();
95     }
96 
97     /**
98      * Generates a key pair. Unless an initialization method is called
99      * using a KeyPairGenerator interface, algorithm-specific defaults
100      * will be used. This will generate a new key pair every time it
101      * is called.
102      *
103      * @return the newly generated {@code KeyPair}
104      */
generateKeyPair()105     public abstract KeyPair generateKeyPair();
106 }
107