bitcoincashjs/lib/pubkey.js

var Point = require('./point');
var bn = require('./bn');
var privkey = require('./privkey');

var Pubkey = function Pubkey(point) {
  if (!(this instanceof Pubkey))
    return new Pubkey(point);
  if (point instanceof Point)
    this.point = point;
  else if (point) {
    var obj = point;
    this.set(obj);
  }
};

Pubkey.prototype.set = function(obj) {
  if (obj.point && !obj.point.getX() && !obj.point.getY())
    throw new Error('Invalid point');
  this.point = obj.point || this.point;
  this.compressed = typeof obj.compressed !== 'undefined' ? obj.compressed : this.compressed;
  return this;
};

Pubkey.prototype.fromPrivkey = function(privkey) {
  this.set({
    point: Point.getG().mul(privkey.bn),
    compressed: privkey.compressed}
  );
  return this;
};

Pubkey.prototype.fromBuffer = function(buf) {
  return this.fromDER(buf);
};

Pubkey.prototype.fromDER = function(buf) {
  if (buf[0] == 0x04) {
    var xbuf = buf.slice(1, 33);
    var ybuf = buf.slice(33, 65);
    if (xbuf.length !== 32 || ybuf.length !== 32 || buf.length !== 65)
      throw new Error('Length of x and y must be 32 bytes');
    var x = bn(xbuf);
    var y = bn(ybuf);
    this.point = Point(x, y);
    this.compressed = false;
  } else if (buf[0] == 0x03) {
    var xbuf = buf.slice(1);
    var x = bn(xbuf);
    this.fromX(true, x);
    this.compressed = true;
  } else if (buf[0] == 0x02) {
    var xbuf = buf.slice(1);
    var x = bn(xbuf);
    this.fromX(false, x);
    this.compressed = true;
  } else {
    throw new Error('Invalid DER format pubkey');
  }
  return this;
};

Pubkey.prototype.fromString = function(str) {
  this.fromDER(new Buffer(str, 'hex'));
};

Pubkey.prototype.fromX = function(odd, x) {
  if (typeof odd !== 'boolean')
    throw new Error('Must specify whether y is odd or not (true or false)');
  this.point = Point.fromX(odd, x);
};

Pubkey.prototype.toBuffer = function() {
  var compressed = typeof this.compressed === 'undefined' ? true : this.compressed;
  return this.toDER(compressed);
};

Pubkey.prototype.toDER = function(compressed) {
  compressed = typeof this.compressed === 'undefined' ? compressed : this.compressed;
  if (typeof compressed !== 'boolean')
    throw new Error('Must specify whether the public key is compressed or not (true or false)');

  var x = this.point.getX();
  var y = this.point.getY();

  var xbuf = x.toBuffer({size: 32});
  var ybuf = y.toBuffer({size: 32});

  if (!compressed) {
    var prefix = new Buffer([0x04]);
    return Buffer.concat([prefix, xbuf, ybuf]);
  } else {
    var odd = ybuf[ybuf.length - 1] % 2;
    if (odd)
      var prefix = new Buffer([0x03]);
    else
      var prefix = new Buffer([0x02]);
    return Buffer.concat([prefix, xbuf]);
  }
};

Pubkey.prototype.toString = function() {
  var compressed = typeof this.compressed === 'undefined' ? true : this.compressed;
  return this.toDER(compressed).toString('hex');
};

//https://www.iacr.org/archive/pkc2003/25670211/25670211.pdf
Pubkey.prototype.validate = function() {
  if (this.point.isInfinity())
    throw new Error('point: Point cannot be equal to Infinity');
  if (this.point.eq(Point(bn(0), bn(0))))
    throw new Error('point: Point cannot be equal to 0, 0');
  this.point.validate();
  return this;
};

module.exports = Pubkey;