J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 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 | |
| 29 | /** |
| 30 | * This immutable class represents a point on an elliptic curve (EC) |
| 31 | * in affine coordinates. Other coordinate systems can |
| 32 | * extend this class to represent this point in other |
| 33 | * coordinates. |
| 34 | * |
| 35 | * @author Valerie Peng |
| 36 | * |
| 37 | * @since 1.5 |
| 38 | */ |
| 39 | public class ECPoint { |
| 40 | |
| 41 | private final BigInteger x; |
| 42 | private final BigInteger y; |
| 43 | |
| 44 | /** |
| 45 | * This defines the point at infinity. |
| 46 | */ |
| 47 | public static final ECPoint POINT_INFINITY = new ECPoint(); |
| 48 | |
| 49 | // private constructor for constructing point at infinity |
| 50 | private ECPoint() { |
| 51 | this.x = null; |
| 52 | this.y = null; |
| 53 | } |
| 54 | |
| 55 | /** |
| 56 | * Creates an ECPoint from the specified affine x-coordinate |
| 57 | * <code>x</code> and affine y-coordinate <code>y</code>. |
| 58 | * @param x the affine x-coordinate. |
| 59 | * @param y the affine y-coordinate. |
| 60 | * @exception NullPointerException if <code>x</code> or |
| 61 | * <code>y</code> is null. |
| 62 | */ |
| 63 | public ECPoint(BigInteger x, BigInteger y) { |
| 64 | if ((x==null) || (y==null)) { |
| 65 | throw new NullPointerException("affine coordinate x or y is null"); |
| 66 | } |
| 67 | this.x = x; |
| 68 | this.y = y; |
| 69 | } |
| 70 | |
| 71 | /** |
| 72 | * Returns the affine x-coordinate <code>x</code>. |
| 73 | * Note: POINT_INFINITY has a null affine x-coordinate. |
| 74 | * @return the affine x-coordinate. |
| 75 | */ |
| 76 | public BigInteger getAffineX() { |
| 77 | return x; |
| 78 | } |
| 79 | |
| 80 | /** |
| 81 | * Returns the affine y-coordinate <code>y</code>. |
| 82 | * Note: POINT_INFINITY has a null affine y-coordinate. |
| 83 | * @return the affine y-coordinate. |
| 84 | */ |
| 85 | public BigInteger getAffineY() { |
| 86 | return y; |
| 87 | } |
| 88 | |
| 89 | /** |
| 90 | * Compares this elliptic curve point for equality with |
| 91 | * the specified object. |
| 92 | * @param obj the object to be compared. |
| 93 | * @return true if <code>obj</code> is an instance of |
| 94 | * ECPoint and the affine coordinates match, false otherwise. |
| 95 | */ |
| 96 | public boolean equals(Object obj) { |
| 97 | if (this == obj) return true; |
| 98 | if (this == POINT_INFINITY) return false; |
| 99 | if (obj instanceof ECPoint) { |
| 100 | return ((x.equals(((ECPoint)obj).x)) && |
| 101 | (y.equals(((ECPoint)obj).y))); |
| 102 | } |
| 103 | return false; |
| 104 | } |
| 105 | |
| 106 | /** |
| 107 | * Returns a hash code value for this elliptic curve point. |
| 108 | * @return a hash code value. |
| 109 | */ |
| 110 | public int hashCode() { |
| 111 | if (this == POINT_INFINITY) return 0; |
| 112 | return x.hashCode() << 5 + y.hashCode(); |
| 113 | } |
| 114 | } |