1 /*
2 * Copyright 2003 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25 package java.security.spec;
26
27 import java.math.BigInteger;
28 import java.util.Arrays;
29
30 /**
31 * This immutable class defines an elliptic curve (EC) prime
32 * finite field.
33 *
34 * @see ECField
35 *
36 * @author Valerie Peng
37 *
38 * @since 1.5
39 */
40 public class ECFieldFp implements ECField {
41
42 private BigInteger p;
43
44 /**
45 * Creates an elliptic curve prime finite field
46 * with the specified prime <code>p</code>.
47 * @param p the prime.
48 * @exception NullPointerException if <code>p</code> is null.
49 * @exception IllegalArgumentException if <code>p</code>
50 * is not positive.
51 */
52 public ECFieldFp(BigInteger p) {
53 if (p.signum() != 1) {
54 throw new IllegalArgumentException("p is not positive");
55 }
56 this.p = p;
57 }
58
59 /**
60 * Returns the field size in bits which is size of prime p
61 * for this prime finite field.
62 * @return the field size in bits.
63 */
64 public int getFieldSize() {
65 return p.bitLength();
66 };
67
68 /**
69 * Returns the prime <code>p</code> of this prime finite field.
70 * @return the prime.
71 */
72 public BigInteger getP() {
73 return p;
74 }
75
76 /**
77 * Compares this prime finite field for equality with the
78 * specified object.
79 * @param obj the object to be compared.
80 * @return true if <code>obj</code> is an instance
81 * of ECFieldFp and the prime value match, false otherwise.
82 */
83 public boolean equals(Object obj) {
84 if (this == obj) return true;
85 if (obj instanceof ECFieldFp) {
86 return (p.equals(((ECFieldFp)obj).p));
87 }
88 return false;
89 }
90
91 /**
92 * Returns a hash code value for this prime finite field.
93 * @return a hash code value.
94 */
95 public int hashCode() {
96 return p.hashCode();
97 }
98 }
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