146 lines
3.6 KiB
JavaScript
146 lines
3.6 KiB
JavaScript
'use strict';
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var BN = require('./bn');
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var BufferUtil = require('../util/buffer');
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var ec = require('elliptic').curves.secp256k1;
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var ecPoint = ec.curve.point.bind(ec.curve);
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var ecPointFromX = ec.curve.pointFromX.bind(ec.curve);
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/**
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*
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* Instantiate a valid secp256k1 Point from the X and Y coordinates.
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*
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* @param {BN|String} x - The X coordinate
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* @param {BN|String} y - The Y coordinate
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* @link https://github.com/indutny/elliptic
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* @augments elliptic.curve.point
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* @throws {Error} A validation error if exists
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* @returns {Point} An instance of Point
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* @constructor
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*/
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var Point = function Point(x, y, isRed) {
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var point = ecPoint(x, y, isRed);
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point.validate();
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return point;
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};
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Point.prototype = Object.getPrototypeOf(ec.curve.point());
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/**
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*
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* Instantiate a valid secp256k1 Point from only the X coordinate
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*
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* @param {boolean} odd - If the Y coordinate is odd
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* @param {BN|String} x - The X coordinate
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* @throws {Error} A validation error if exists
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* @returns {Point} An instance of Point
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*/
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Point.fromX = function fromX(odd, x){
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var point = ecPointFromX(odd, x);
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point.validate();
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return point;
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};
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/**
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*
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* Will return a secp256k1 ECDSA base point.
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*
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* @link https://en.bitcoin.it/wiki/Secp256k1
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* @returns {Point} An instance of the base point.
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*/
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Point.getG = function getG() {
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return ec.curve.g;
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};
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/**
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*
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* Will return the max of range of valid private keys as governed by the secp256k1 ECDSA standard.
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*
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* @link https://en.bitcoin.it/wiki/Private_key#Range_of_valid_ECDSA_private_keys
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* @returns {BN} A BN instance of the number of points on the curve
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*/
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Point.getN = function getN() {
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return new BN(ec.curve.n.toArray());
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};
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Point.prototype._getX = Point.prototype.getX;
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/**
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*
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* Will return the X coordinate of the Point
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*
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* @returns {BN} A BN instance of the X coordinate
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*/
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Point.prototype.getX = function getX() {
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return new BN(this._getX().toArray());
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};
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Point.prototype._getY = Point.prototype.getY;
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/**
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*
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* Will return the Y coordinate of the Point
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*
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* @returns {BN} A BN instance of the Y coordinate
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*/
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Point.prototype.getY = function getY() {
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return new BN(this._getY().toArray());
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};
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/**
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*
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* Will determine if the point is valid
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*
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* @link https://www.iacr.org/archive/pkc2003/25670211/25670211.pdf
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* @param {Point} An instance of Point
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* @throws {Error} A validation error if exists
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* @returns {Point} An instance of the same Point
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*/
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Point.prototype.validate = function validate() {
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if (this.isInfinity()){
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throw new Error('Point cannot be equal to Infinity');
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}
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if (this.getX().cmp(BN.Zero) === 0 || this.getY().cmp(BN.Zero) === 0){
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throw new Error('Invalid x,y value for curve, cannot equal 0.');
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}
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var p2 = ecPointFromX(this.getY().isOdd(), this.getX());
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if (p2.y.cmp(this.y) !== 0) {
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throw new Error('Invalid y value for curve.');
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}
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var xValidRange = (this.getX().gt(BN.Minus1) && this.getX().lt(Point.getN()));
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var yValidRange = (this.getY().gt(BN.Minus1) && this.getY().lt(Point.getN()));
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if ( !xValidRange || !yValidRange ) {
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throw new Error('Point does not lie on the curve');
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}
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//todo: needs test case
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if (!(this.mul(Point.getN()).isInfinity())) {
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throw new Error('Point times N must be infinity');
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}
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return this;
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};
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Point.pointToCompressed = function pointToCompressed(point) {
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var xbuf = point.getX().toBuffer({size: 32});
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var ybuf = point.getY().toBuffer({size: 32});
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var prefix;
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var odd = ybuf[ybuf.length - 1] % 2;
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if (odd) {
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prefix = new Buffer([0x03]);
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} else {
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prefix = new Buffer([0x02]);
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}
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return BufferUtil.concat([prefix, xbuf]);
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};
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module.exports = Point;
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