Brainwallet bitcoinsig with bitcoinjs-lib 1.0.3 - And a bug

gistfile1.js

/**
 * Created by Kevin Tam on 08/08/2014.
 */

var Base58 = require('bs58');
var Crypto = require('crypto');
var BigInteger = require('bigi');
var assert = require('assert');
var Bitcoin = require('../../')

function msg_numToVarInt(i) {
    if (i < 0xfd) {
        return [i];
    } else if (i <= 0xffff) {
        // can't use numToVarInt from bitcoinjs, BitcoinQT wants big endian here (!)
        return [0xfd, i & 255, i >>> 8];
    } else {
        throw ("message too large");
    }
}

function sha256(b) {
    return Bitcoin.crypto.sha256(b);
}


function msg_bytes(message) {
    var b = new Buffer(message, 'UTF8');
    return Buffer.concat([new Buffer(msg_numToVarInt(b.length)), b]);
}

function msg_digest(message) {
    //var b = msg_bytes("Bitcoin Signed Message:\n").concat(msg_bytes(message));
    var b = Buffer.concat([msg_bytes("Bitcoin Signed Message:\n"), msg_bytes(message)]);
    // console.log("To hash:" + new Buffer(b).toString("base64"));
    return sha256(sha256(new Buffer(b)));
}

function bitcoinsig_test() {
    var k = '5JeWZ1z6sRcLTJXdQEDdB986E6XfLAkj9CgNE4EHzr5GmjrVFpf';
    var a = '17mDAmveV5wBwxajBsY7g1trbMW1DVWcgL';
    var s = 'HDiv4Oe9SjM1FFVbKk4m3N34efYiRgkQGGoEm564ldYt44jHVTuX23+WnihNMi4vujvpUs1M529P3kftjDezn9E=';
    var m = 'test message';
    // Beware passing this into other libs! http://www.mattesch.info/blog/the-instanceof-trap-in-node-js/
    var Ecurve = require("ecurve");
    var secp256k1 = Ecurve.getCurveByName('secp256k1');
    // When dcousen fixes it, replace ECurve with this
    //var secp256k1 = Bitcoin.ECKey.curve;

    // Part un - Verify pre-signed message
    var siginfo = new Bitcoin.ECSignature.parseCompact(new Buffer(s,"base64"));
    var hash =  msg_digest(m);
    assert.equal(hash.toString("base64"), "EiYXnd9jg/vPUQLJSSU4tyBsc5rnnrBkQIwqvWfTm+0=");
    // hash.toString("base64") ‌9YdKhI6dqPsHun4O6UIhoLHRyx8VOaEBpJPd/7z4TQU=
    var e = BigInteger.fromBuffer(hash);
    var pubkeyQ = Bitcoin.ecdsa.recoverPubKey(secp256k1, e, siginfo.signature, siginfo.i);
    // FIXME: bitcoinjs-lib 1.0.3 throws a instanceof exception on next line due to external Ecurve
    var pubkey = new Bitcoin.ECPubKey(pubkeyQ, siginfo.compressed);
    assert.equal(pubkey.getAddress().toBase58Check(), a, "Extract pub address from signature should match pub addr");
    var v1 = Bitcoin.ecdsa.verify(secp256k1, hash, siginfo.signature, pubkeyQ);
    assert(v1, "Signature should pass");
    // Part deux - do signing and reverify
    var payload = Base58.decode(k);
    var priv = Bitcoin.ECKey.fromWIF(k)
    var sig = priv.sign(hash);
    var v2 = Bitcoin.ecdsa.verify(secp256k1, hash, siginfo.signature, pubkeyQ);
    assert(v2, "Signature should pass after re-signing")
}

bitcoinsig_test();