114 lines
3.5 KiB
Java
114 lines
3.5 KiB
Java
/*
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* Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.security.spec;
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import java.math.BigInteger;
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/**
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* This immutable class represents a point on an elliptic curve (EC)
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* in affine coordinates. Other coordinate systems can
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* extend this class to represent this point in other
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* coordinates.
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*
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* @author Valerie Peng
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*
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* @since 1.5
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*/
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public class ECPoint {
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private final BigInteger x;
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private final BigInteger y;
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/**
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* This defines the point at infinity.
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*/
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public static final ECPoint POINT_INFINITY = new ECPoint();
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// private constructor for constructing point at infinity
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private ECPoint() {
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this.x = null;
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this.y = null;
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}
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/**
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* Creates an ECPoint from the specified affine x-coordinate
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* {@code x} and affine y-coordinate {@code y}.
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* @param x the affine x-coordinate.
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* @param y the affine y-coordinate.
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* @throws NullPointerException if {@code x} or
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* {@code y} is null.
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*/
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public ECPoint(BigInteger x, BigInteger y) {
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if ((x==null) || (y==null)) {
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throw new NullPointerException("affine coordinate x or y is null");
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}
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this.x = x;
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this.y = y;
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}
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/**
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* Returns the affine x-coordinate {@code x}.
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* Note: POINT_INFINITY has a null affine x-coordinate.
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* @return the affine x-coordinate.
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*/
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public BigInteger getAffineX() {
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return x;
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}
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/**
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* Returns the affine y-coordinate {@code y}.
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* Note: POINT_INFINITY has a null affine y-coordinate.
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* @return the affine y-coordinate.
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*/
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public BigInteger getAffineY() {
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return y;
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}
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/**
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* Compares this elliptic curve point for equality with
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* the specified object.
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* @param obj the object to be compared.
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* @return true if {@code obj} is an instance of
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* ECPoint and the affine coordinates match, false otherwise.
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*/
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public boolean equals(Object obj) {
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if (this == obj) return true;
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if (this == POINT_INFINITY) return false;
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return obj instanceof ECPoint other
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&& ((x.equals(other.x))
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&& (y.equals(other.y)));
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}
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/**
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* Returns a hash code value for this elliptic curve point.
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* @return a hash code value.
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*/
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public int hashCode() {
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if (this == POINT_INFINITY) return 0;
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return x.hashCode() << 5 + y.hashCode();
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}
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}
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