The title is a statement of Kerkhoffs' principle. A cryptographic system is only secure if the security of the system doesn't depend on the whole system being secret. And there's an interesting lesson there for Diebold. You see Diebold sells ATMs and voting machines. And they posted pictures of the key that allegedly opens every voting machine they sell.
Ross Kinard looked at the key (they're for sale on Diebold's web site) and using some blank keys from Ace Hardware, made some keys, and sent them to Alex Haldeman, who blogs about it in "Diebold Shows How to Make Your Own Voting Machine Key." Alex also reports that Diebold has removed the picture, now all over the internet, of their key.
I hope it can be easily changed, and I wonder if there's a single key for ATM machines?
Also, thanks to the several friends who sent this to me!