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25 
26 package java.security.spec;
27 
28 import java.security.InvalidParameterException;
29 import java.util.Objects;
30 import java.util.Optional;
31 
32 /**
33  * A class used to specify EdDSA signature and verification parameters. All
34  * algorithm modes in <a href="https://tools.ietf.org/html/rfc8032">RFC 8032:
35  * Edwards-Curve Digital Signature Algorithm (EdDSA)</a> can be specified using
36  * combinations of the settings in this class.
37  *
38  * <ul>
39  * <li>If prehash is true, then the mode is Ed25519ph or Ed448ph</li>
40  * <li>Otherwise, if a context is present, the mode is Ed25519ctx or Ed448</li>
41  * <li>Otherwise, the mode is Ed25519 or Ed448</li>
42  * </ul>
43  *
44  * @since 15
45  */
46 
47 public class EdDSAParameterSpec implements AlgorithmParameterSpec {
48 
49     private final boolean prehash;
50     private final byte[] context;
51 
52     /**
53      * Construct an {@code EdDSAParameterSpec} by specifying whether the prehash mode
54      * is used. No context is provided so this constructor specifies a mode
55      * in which the context is null. Note that this mode may be different
56      * than the mode in which an empty array is used as the context.
57      *
58      * @param prehash whether the prehash mode is specified.
59      */
EdDSAParameterSpec(boolean prehash)60     public EdDSAParameterSpec(boolean prehash) {
61         this.prehash = prehash;
62         this.context = null;
63     }
64 
65     /**
66      * Construct an {@code EdDSAParameterSpec} by specifying a context and whether the
67      * prehash mode is used. The context may not be null, but it may be an
68      * empty array. The mode used when the context is an empty array may not be
69      * the same as the mode used when the context is absent.
70      *
71      * @param prehash whether the prehash mode is specified.
72      * @param context the context is copied and bound to the signature.
73      * @throws NullPointerException if context is null.
74      * @throws InvalidParameterException if context length is greater than 255.
75      */
EdDSAParameterSpec(boolean prehash, byte[] context)76     public EdDSAParameterSpec(boolean prehash, byte[] context) {
77 
78         Objects.requireNonNull(context, "context may not be null");
79         if (context.length > 255) {
80             throw new InvalidParameterException("context length cannot be " +
81                 "greater than 255");
82         }
83 
84         this.prehash = prehash;
85         this.context = context.clone();
86     }
87 
88     /**
89      * Get whether the prehash mode is specified.
90      *
91      * @return whether the prehash mode is specified.
92      */
isPrehash()93     public boolean isPrehash() {
94         return prehash;
95     }
96 
97     /**
98      * Get the context that the signature will use.
99      *
100      * @return {@code Optional} contains a copy of the context or empty
101      * if context is null.
102      */
getContext()103     public Optional<byte[]> getContext() {
104         if (context == null) {
105             return Optional.empty();
106         } else {
107             return Optional.of(context.clone());
108         }
109     }
110 }
111