最近项目，经常用到了加密板块，这里收集了一下常规的用法

var crypto = require('crypto');
exports.encrypt = function (str, secret) {
  var cipher = crypto.createCipher('aes192', secret);
  var enc = cipher.update(str, 'utf8', 'hex');
  enc += cipher.final('hex');
  return enc;
};

exports.decrypt = function (str, secret) {
  var decipher = crypto.createDecipher('aes192', secret);
  var dec = decipher.update(str, 'hex', 'utf8');
  dec += decipher.final('utf8');
  return dec;
};

exports.md5 = function (str) {
  var md5sum = crypto.createHash('md5');
  md5sum.update(str);
  str = md5sum.digest('hex');
  return str;
};

exports.randomString = function (size) {
  size = size || 6;
  var code_string = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
  var max_num = code_string.length + 1;
  var new_pass = '';
  while (size > 0) {
  new_pass += code_string.charAt(Math.floor(Math.random() * max_num));
  size–;
};