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25 package java.security.spec;
26 
27 import java.math.BigInteger;
28 
29 /**
30  * This immutable class specifies the set of domain parameters
31  * used with elliptic curve cryptography (ECC).
32  *
33  * @see AlgorithmParameterSpec
34  *
35  * @author Valerie Peng
36  *
37  * @since 1.5
38  */
39 public class ECParameterSpec implements AlgorithmParameterSpec {
40 
41     private final EllipticCurve curve;
42     private final ECPoint g;
43     private final BigInteger n;
44     private final int h;
45 
46     /**
47      * Creates elliptic curve domain parameters based on the
48      * specified values.
49      * @param curve the elliptic curve which this parameter
50      * defines.
51      * @param g the generator which is also known as the base point.
52      * @param n the order of the generator {@code g}.
53      * @param h the cofactor.
54      * @throws    NullPointerException if {@code curve},
55      * {@code g}, or {@code n} is null.
56      * @throws    IllegalArgumentException if {@code n}
57      * or {@code h} is not positive.
58      */
ECParameterSpec(EllipticCurve curve, ECPoint g, BigInteger n, int h)59     public ECParameterSpec(EllipticCurve curve, ECPoint g,
60                            BigInteger n, int h) {
61         if (curve == null) {
62             throw new NullPointerException("curve is null");
63         }
64         if (g == null) {
65             throw new NullPointerException("g is null");
66         }
67         if (n == null) {
68             throw new NullPointerException("n is null");
69         }
70         if (n.signum() != 1) {
71             throw new IllegalArgumentException("n is not positive");
72         }
73         if (h <= 0) {
74             throw new IllegalArgumentException("h is not positive");
75         }
76         this.curve = curve;
77         this.g = g;
78         this.n = n;
79         this.h = h;
80     }
81 
82     /**
83      * Returns the elliptic curve that this parameter defines.
84      * @return the elliptic curve that this parameter defines.
85      */
getCurve()86     public EllipticCurve getCurve() {
87         return curve;
88     }
89 
90     /**
91      * Returns the generator which is also known as the base point.
92      * @return the generator which is also known as the base point.
93      */
getGenerator()94     public ECPoint getGenerator() {
95         return g;
96     }
97 
98     /**
99      * Returns the order of the generator.
100      * @return the order of the generator.
101      */
getOrder()102     public BigInteger getOrder() {
103         return n;
104     }
105 
106     /**
107      * Returns the cofactor.
108      * @return the cofactor.
109      */
getCofactor()110     public int getCofactor() {
111         return h;
112     }
113 }
114