code: function(key, data) {
          var shaObj = new Sha('SHA-256', 'TEXT');
          shaObj.setHMACKey(key, 'TEXT');
          shaObj.update(data);
          return shaObj.getHMAC('HEX');
      }
docs: Generate a SHA256 HMAC hash from the given data
  
  @param  {String} key
  @param  {String} data
  @return {String}