bitcoincashjs/lib/browser/Key.js

var SecureRandom = require('../SecureRandom');
var bignum = require('bignum');
var elliptic = require('elliptic');
var Point = require('./Point');
var CommonKey = require('../common/Key');
var util = require('util');

var Key = function() {
  this._pub = null;
  this._compressed = true; // default
};

for (var i in CommonKey) {
  if (CommonKey.hasOwnProperty(i))
    Key[i] = CommonKey[i];
}

var bufferToArray = Key.bufferToArray = function(buffer) {
  var ret = [];

  var l = buffer.length;
  for (var i = 0; i < l; i++) {
    ret.push(buffer.readUInt8(i));
  }

  return ret;
}

Object.defineProperty(Key.prototype, 'public', {
  set: function(p) {
    if (!Buffer.isBuffer(p)) {
      throw new Error('Arg should be a buffer');
    }
    var type = p[0];
    this._compressed = type !== 0x04;
    this._pub = p;
  },
  get: function() {
    return this._pub;
  }
});

Object.defineProperty(Key.prototype, 'compressed', {
  set: function(c) {
    var oldc = this._compressed;
    this._compressed = !!c;
    if (oldc == this._compressed)
      return;
    var oldp = this._pub;
    if (this._pub) {
      if (this._compressed) {
        var xbuf = this._pub.slice(1, 33);
        var ybuf = this._pub.slice(33, 65);
        var x = new bignum(xbuf);
        var y = new bignum(ybuf);
        var p = new Point(x, y);
        this._pub = p.toCompressedPubKey();
      } else {
        var ec = elliptic.curves.secp256k1;
        var xbuf = this._pub.slice(1, 33);
        var odd = this._pub[0] == 3 ? true : false;
        var p = ec.curve.pointFromX(odd, xbuf);
        var ybuf = new Buffer(p.y.toArray());
        var xb = new bignum(xbuf);
        var yb = new bignum(ybuf);
        var pb = new Point(xb, yb);
        this._pub = pb.toUncompressedPubKey();
      }
    }
    if (!this._compressed) {
      //bug in eckey
      //oldp.slice(1).copy(this._pub, 1);
    }
  },
  get: function() {
    return this._compressed;
  }
});

Key.generateSync = function() {
  var privbuf;

  var ec = elliptic.curves.secp256k1;
  while (true) {
    privbuf = SecureRandom.getRandomBuffer(32);
    if ((bignum.fromBuffer(privbuf, {
      size: 32
    })).cmp(ec.n) < 0)
      break;
  }

  var key = new Key();
  key.private = privbuf;
  key.regenerateSync();
  return key;
};

Key.prototype.regenerateSync = function() {
  if (!this.private) {
    throw new Error('Key does not have a private key set');
  }

  var ec = elliptic.curves.secp256k1;
  var g = ec.g;
  var ecp = ec.g.mul(this.private);
  var x = new bignum(ecp.x.toArray());
  var y = new bignum(ecp.y.toArray());
  var p = new Point(x, y);
  if (this.compressed)
    this._pub = p.toCompressedPubKey();
  else
    this._pub = p.toUncompressedPubKey();

  return this;
};

Key.prototype.signSync = function(hash) {
  var ec = elliptic.curves.secp256k1;

  if (!this.private) {
    throw new Error('Key does not have a private key set');
  }

  if (!Buffer.isBuffer(hash) || hash.length !== 32) {
    throw new Error('Arg should be a 32 bytes hash buffer');
  }
  var privnum = new bignum(this.private);
  var sigrs = Key.sign(hash, privnum);
  var der = Key.rs2DER(sigrs.r, sigrs.s);

  return der;
};

Key.prototype.verifySignature = function(hash, sig, callback) {
  try {
    var result = this.verifySignatureSync(hash, sig);
    callback(null, result);
  } catch (e) {
    callback(e);
  }
};

Key.prototype.verifySignatureSync = function(hash, sig) {
  var ec = new elliptic.ec(elliptic.curves.secp256k1);
  var msg = hash.toString('hex');
  var pub = this._pub.toString('hex');
  var sig = sig.toString('hex');
  var v = ec.verify(msg, sig, pub);
  return v;
};

Key.sign = function(hash, priv, k) {
  var d = priv;
  var n = Point.getN();
  var e = new bignum(hash);

  do {
    var k = k || Key.genk();
    var G = Point.getG();
    var Q = Point.multiply(G, k);
    var r = Q.x.mod(n);
    var s = k.invm(n).mul(e.add(d.mul(r))).mod(n);
  } while (r.cmp(new bignum(0)) <= 0 || s.cmp(new bignum(0)) <= 0);

  return {r: r, s: s};
};

Key.signCompressed = function(hash, priv, k) {
  var sig = Key.sign(hash, priv, k);
  var r = sig.r;
  var s = sig.s;
  var e = bignum.fromBuffer(hash);

  var G = Point.getG();
  var Q = Point.multiply(G, priv);

  var i = Key.calcPubKeyRecoveryParam(e, r, s, Q);

  var rbuf = r.toBuffer({size: 32});
  var sbuf = s.toBuffer({size: 32});
  var ibuf = new Buffer([i]);
  var buf = Buffer.concat([ibuf, rbuf, sbuf]);
  return buf;
};

Key.verifyCompressed = function(hash, sigbuf) {
  if (sigbuf.length !== 1 + 32 + 32)
    throw new Error("Invalid length for sigbuf");

  var i = sigbuf[0];
  if (i < 0 || i > 3)
    throw new Error("Invalid value for i");

  var rbuf = sigbuf.slice(1, 1 + 32);
  var sbuf = sigbuf.slice(1 + 32, 1 + 32 + 32);
  var r = bignum.fromBuffer(rbuf);
  var s = bignum.fromBuffer(sbuf);

  var sigDER = Key.rs2DER(r, s);

  var e = bignum.fromBuffer(hash);

  var key = new Key();
  var pub = Key.recoverPubKey(e, r, s, i);
  var pubbuf = pub.toCompressedPubKey();
  key.public = pubbuf;

  return key.verifySignatureSync(hash, sigDER);
};

module.exports = Key;