code: function signTransaction (trs, secret) {
  	var keys = crypto.getKeys(secret);
  	var signature = crypto.multiSign(trs, keys);
  
  	return {
  		transaction: trs.id,
  		signature: signature
  	};
  }
docs: @method createDapp
  @param trs transaction object
  @param secret
  
  @return {string}