CriticismWhat's keeping this thief from cutting your rope, or the fabric of your backpack, for that matter?
Potential SolutionThat being said, if a knot and a padlock was your only option, I would tie two alpine butterfly knots (
https://en.wikipedia.org/wiki/Butterfly_loop), one on each cord, and put your lock through the loops. Because of the structure of the knot, it could not be untied without removing your padlock. The drawstring bag would only be able to open a little bit if the knots were tied near the opening. Not enough for the thief to steal your laptop or whatever.
Drawbacks of Solution- The cord can be cut
- The thief could potentially work slack through the knots and move them to the bottom of the cord, allowing them to open your bag
- They would have to be untied and re-tied every time you opened/closed your bag.