Idea of Padlock Icon
This icon looks just like a padlock. The base of the lock is a square with slightly rounded edges. There is a circular shape in the center that looks just like where you would place a key. The hasp of the lock is on top and is simply a half circle tilted slightly to the left to indicate the lock is open.
This page shows the different variations of the Padlock from an Icons8 icon pack. Feel free to resize and recolor the icon, and then download the icon in PNG format for free.