That's what the Secret Knock Activated Drawer Lock does. It hides all of the lock mechanism away and can only be unlocked by something you know: a secret pattern of knocks.
A solenoid locks secures the drawer while a piezo buzzer listens for knocks. A Trinket compares the knock pattern to the stored secret knock and if they match the solenoid latch retracts and the drawer can be opened. Setting your own custom knock is as simple as holding down a button and tapping the new rhythm.
The project is relatively straight forward and you should be able to complete it in an afternoon.
As always, read and understand this guide completely before starting the project.