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/*
* Protocol-Attacker - A Framework to create Protocol Analysis Tools
*
* Copyright 2023-2023 Ruhr University Bochum, Paderborn University, Technology Innovation Institute, and Hackmanit GmbH
*
* Licensed under Apache License, Version 2.0
* http://www.apache.org/licenses/LICENSE-2.0.txt
*/
package de.rub.nds.protocol.crypto.ec;
import de.rub.nds.protocol.constants.GroupParameters;
import de.rub.nds.protocol.crypto.CyclicGroup;
import jakarta.xml.bind.annotation.XmlAccessType;
import jakarta.xml.bind.annotation.XmlAccessorType;
import jakarta.xml.bind.annotation.XmlElement;
import jakarta.xml.bind.annotation.XmlElements;
import jakarta.xml.bind.annotation.XmlRootElement;
import java.io.Serializable;
import java.math.BigInteger;
import java.util.Objects;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
/**
* Can be used to store a point of an elliptic curve.
*
* Affine points store their x and y coordinates. The projective z-coordinate (equal to 1) will
* not be stored. The point at infinity [0:1:0] (the only point with z-coordinate 0) does not store
* any of it's coordinates.
*/
@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class Point implements Serializable {
private static final Logger LOGGER = LogManager.getLogger();
public static Point createPoint(
BigInteger x, BigInteger y, GroupParameters curveParameters) {
CyclicGroup group = curveParameters.getGroup();
EllipticCurve curve;
if (group instanceof EllipticCurve) {
curve = (EllipticCurve) group;
} else {
LOGGER.warn("Cannot create point for non-elliptic curve");
return null;
}
return curve.getPoint(x, y);
}
/*
* Point objects are immutable. This should make deep copies in the methods of the EllipticCurve class unnecessary.
*/
@XmlElements(
value = {
@XmlElement(type = FieldElementF2m.class, name = "xFieldElementF2m"),
@XmlElement(type = FieldElementFp.class, name = "xFieldElementFp")
})
private final FieldElement fieldX;
@XmlElements(
value = {
@XmlElement(type = FieldElementF2m.class, name = "yFieldElementF2m"),
@XmlElement(type = FieldElementFp.class, name = "yFieldElementFp")
})
private final FieldElement fieldY;
private final boolean infinity;
/** Instantiates the point at infinity. */
public Point() {
this.infinity = true;
this.fieldX = null;
this.fieldY = null;
}
/**
* Instantiates an affine point with coordinates x and y. Calling EllipticCurve.getPoint()
* should always be preferred over using this constructor.
*
* @param x A FieldElement representing the x-coordinate of the point.
* @param y A FieldElement representing the y-coordinate of the point. x and y must be elements
* of the same field.
*/
public Point(FieldElement x, FieldElement y) {
this.fieldX = x;
this.fieldY = y;
this.infinity = false;
}
/**
* Returns true if the point is the point at infinity. Returns false if the point is an affine
* point.
*/
public boolean isAtInfinity() {
return this.infinity;
}
public FieldElement getFieldX() {
return this.fieldX;
}
public FieldElement getFieldY() {
return this.fieldY;
}
@Override
public int hashCode() {
int hash = 7;
hash = 89 * hash + Objects.hashCode(this.fieldX);
hash = 89 * hash + Objects.hashCode(this.fieldY);
hash = 89 * hash + (this.infinity ? 1 : 0);
return hash;
}
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj == null) {
return false;
}
if (getClass() != obj.getClass()) {
return false;
}
final Point other = (Point) obj;
if (this.infinity != other.infinity) {
return false;
}
if (!Objects.equals(this.fieldX, other.fieldX)) {
return false;
}
if (!Objects.equals(this.fieldY, other.fieldY)) {
return false;
}
return true;
}
@Override
public String toString() {
if (this.isAtInfinity()) {
return "Point: Infinity";
} else {
return "Point: ("
+ this.getFieldX().toString()
+ ", "
+ this.getFieldY().toString()
+ ")";
}
}
}