"Much of the work was top secret," says fish. "We could do engineering and manufacturing bill-of-material implosions on not-yet-made-public warplanes."

And naturally, the security extends to the DP department's physical offices, where the door opens with a keypad. "My boss, the supervisor of technical support, reset the code every week," fish says.

"One morning when I was entering the pass code, I fat-fingered the keys and hit two at once. I entered the remainder of the code correctly.

"The door opened!"

Fish immediately generalizes what he's observed: There are four numbers in the keycode. Apparently it doesn't matter what other keys are pressed, so long as the correct key is punched.