var crypto = require('crypto');
var int64 = require('int64-native');

var md5Hash = crypto.createHash('md5');
var steamId = new int64('76561197996545192'); // The steamid must be a STRING! not a number!

md5Hash.update('BE');
for (var i = 0; i < 8; i++) {
	md5Hash.update(String.fromCharCode(steamId.and(0xFF).toNumber()));
	steamId = steamId.shiftRight(8);
}

console.log(md5Hash.digest('hex'));