Tired of coming up with random computer passwords, then having to remember them and/or find a place to hide them when you write them down? How would you like to be able to keep your computer passwords written in plain sight — but no one but you can read them?

This is an idea I came up with a while back. The idea is to place it flat against a sheet of paper and write a computer password in the slots. Then remove the key chain and fill in the spaces between the password letters.

The result isn’t unbreakable, but a would-be codebreaker would need to try millions of combinations to figure out the password without the help of the key.

In action, it works like this:

Originally, I intended this to be 3D printed for the Makerbot, which still sounds like a fun idea, but then I realized that all you really need is to cut a 3×5 notecard down to wallet size and write (scrawl?) ‘tick’ marks along the lower edge, so that it would work like so:

Of course, if someone finds your password key chain and/or card, they can read all your passwords. But when I was working in a corporate office, a lot of people kept their passwords openly written on sheets of paper taped to those little slider tables that pull out from desks.

Or they used 123456789 for a password. That’s ineffective too.