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ECPoint.java
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114 lines (104 loc) · 2.61 KB
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/*
* Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package java.security.spec;
import java.math.BigInteger;
/**
* This immutable class represents a point on an elliptic curve (EC)
* in affine coordinates. Other coordinate systems can
* extend this class to represent this point in other
* coordinates.
*
* @author Valerie Peng
*
* @since 1.5
*/
public class ECPoint {
private final BigInteger x;
private final BigInteger y;
/**
* This defines the point at infinity.
*/
public static final ECPoint POINT_INFINITY = new ECPoint();
// private constructor for constructing point at infinity
private ECPoint() {
this.x = null;
this.y = null;
}
/**
* Creates an ECPoint from the specified affine x-coordinate
* {@code x} and affine y-coordinate {@code y}.
* @param x the affine x-coordinate.
* @param y the affine y-coordinate.
* @exception NullPointerException if {@code x} or
* {@code y} is null.
*/
public ECPoint(BigInteger x, BigInteger y) {
if ((x==null) || (y==null)) {
throw new NullPointerException("affine coordinate x or y is null");
}
this.x = x;
this.y = y;
}
/**
* Returns the affine x-coordinate {@code x}.
* Note: POINT_INFINITY has a null affine x-coordinate.
* @return the affine x-coordinate.
*/
public BigInteger getAffineX() {
return x;
}
/**
* Returns the affine y-coordinate {@code y}.
* Note: POINT_INFINITY has a null affine y-coordinate.
* @return the affine y-coordinate.
*/
public BigInteger getAffineY() {
return y;
}
/**
* Compares this elliptic curve point for equality with
* the specified object.
* @param obj the object to be compared.
* @return true if {@code obj} is an instance of
* ECPoint and the affine coordinates match, false otherwise.
*/
public boolean equals(Object obj) {
if (this == obj) return true;
if (this == POINT_INFINITY) return false;
if (obj instanceof ECPoint) {
return ((x.equals(((ECPoint)obj).x)) &&
(y.equals(((ECPoint)obj).y)));
}
return false;
}
/**
* Returns a hash code value for this elliptic curve point.
* @return a hash code value.
*/
public int hashCode() {
if (this == POINT_INFINITY) return 0;
return x.hashCode() << 5 + y.hashCode();
}
}