1 /*
   2  * Copyright (c) 2003, Oracle and/or its affiliates. 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.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * 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 }