This is a Padlock icon. We've made it in iOS style, first introduced in iOS version 7 and supported in all later releases up until now (at least iOS 11). This style is based on thin two-pixel lines and is optimized for 50x50 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 12,700 icons, all in the same style and quality.
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.