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26 package java.security.spec;
27 
28 import java.math.BigInteger;
29 
30 /**
31  * This immutable class specifies the set of domain parameters
32  * used with elliptic curve cryptography (ECC).
33  *
34  * @see AlgorithmParameterSpec
35  *
36  * @author Valerie Peng
37  *
38  * @since 1.5
39  */
40 public class ECParameterSpec implements AlgorithmParameterSpec {
41 
42     private final EllipticCurve curve;
43     private final ECPoint g;
44     private final BigInteger n;
45     private final int h;
46 
47     /**
48      * Creates elliptic curve domain parameters based on the
49      * specified values.
50      * @param curve the elliptic curve which this parameter
51      * defines.
52      * @param g the generator which is also known as the base point.
53      * @param n the order of the generator <code>g</code>.
54      * @param h the cofactor.
55      * @exception NullPointerException if <code>curve</code>,
56      * <code>g</code>, or <code>n</code> is null.
57      * @exception IllegalArgumentException if <code>n</code>
58      * or <code>h</code> is not positive.
59      */
ECParameterSpec(EllipticCurve curve, ECPoint g, BigInteger n, int h)60     public ECParameterSpec(EllipticCurve curve, ECPoint g,
61                            BigInteger n, int h) {
62         if (curve == null) {
63             throw new NullPointerException("curve is null");
64         }
65         if (g == null) {
66             throw new NullPointerException("g is null");
67         }
68         if (n == null) {
69             throw new NullPointerException("n is null");
70         }
71         if (n.signum() != 1) {
72             throw new IllegalArgumentException("n is not positive");
73         }
74         if (h <= 0) {
75             throw new IllegalArgumentException("h is not positive");
76         }
77         this.curve = curve;
78         this.g = g;
79         this.n = n;
80         this.h = h;
81     }
82 
83     /**
84      * Returns the elliptic curve that this parameter defines.
85      * @return the elliptic curve that this parameter defines.
86      */
getCurve()87     public EllipticCurve getCurve() {
88         return curve;
89     }
90 
91     /**
92      * Returns the generator which is also known as the base point.
93      * @return the generator which is also known as the base point.
94      */
getGenerator()95     public ECPoint getGenerator() {
96         return g;
97     }
98 
99     /**
100      * Returns the order of the generator.
101      * @return the order of the generator.
102      */
getOrder()103     public BigInteger getOrder() {
104         return n;
105     }
106 
107     /**
108      * Returns the cofactor.
109      * @return the cofactor.
110      */
getCofactor()111     public int getCofactor() {
112         return h;
113     }
114     // ----- BEGIN android -----
115     private String curveName;
116 
117     /**
118      * Used to set the curve name if available.
119      *
120      * @hide
121      */
setCurveName(String curveName)122     public void setCurveName(String curveName) {
123         this.curveName = curveName;
124     }
125 
126     /**
127      * Returns the name of the curve if this is a named curve. Returns
128      * {@code null} if this is not known to be a named curve.
129      *
130      * @hide
131      */
getCurveName()132     public String getCurveName() {
133         return curveName;
134     }
135     // ----- END android -----
136 }
137