001 /*
002 * Copyright 2003 Sun Microsystems, Inc. All Rights Reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation. Sun designates this
008 * particular file as subject to the "Classpath" exception as provided
009 * by Sun in the LICENSE file that accompanied this code.
010 *
011 * This code is distributed in the hope that it will be useful, but WITHOUT
012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014 * version 2 for more details (a copy is included in the LICENSE file that
015 * accompanied this code).
016 *
017 * You should have received a copy of the GNU General Public License version
018 * 2 along with this work; if not, write to the Free Software Foundation,
019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020 *
021 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022 * CA 95054 USA or visit www.sun.com if you need additional information or
023 * have any questions.
024 */
025 package java.security.spec;
026
027 import java.math.BigInteger;
028 import java.util.Arrays;
029
030 /**
031 * This immutable class defines an elliptic curve (EC) prime
032 * finite field.
033 *
034 * @see ECField
035 *
036 * @author Valerie Peng
037 * @version 1.10, 05/05/07
038 *
039 * @since 1.5
040 */
041 public class ECFieldFp implements ECField {
042
043 private BigInteger p;
044
045 /**
046 * Creates an elliptic curve prime finite field
047 * with the specified prime <code>p</code>.
048 * @param p the prime.
049 * @exception NullPointerException if <code>p</code> is null.
050 * @exception IllegalArgumentException if <code>p</code>
051 * is not positive.
052 */
053 public ECFieldFp(BigInteger p) {
054 if (p.signum() != 1) {
055 throw new IllegalArgumentException("p is not positive");
056 }
057 this .p = p;
058 }
059
060 /**
061 * Returns the field size in bits which is size of prime p
062 * for this prime finite field.
063 * @return the field size in bits.
064 */
065 public int getFieldSize() {
066 return p.bitLength();
067 };
068
069 /**
070 * Returns the prime <code>p</code> of this prime finite field.
071 * @return the prime.
072 */
073 public BigInteger getP() {
074 return p;
075 }
076
077 /**
078 * Compares this prime finite field for equality with the
079 * specified object.
080 * @param obj the object to be compared.
081 * @return true if <code>obj</code> is an instance
082 * of ECFieldFp and the prime value match, false otherwise.
083 */
084 public boolean equals(Object obj) {
085 if (this == obj)
086 return true;
087 if (obj instanceof ECFieldFp) {
088 return (p.equals(((ECFieldFp) obj).p));
089 }
090 return false;
091 }
092
093 /**
094 * Returns a hash code value for this prime finite field.
095 * @return a hash code value.
096 */
097 public int hashCode() {
098 return p.hashCode();
099 }
100 }
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