Someday I want to make a micro enigma cipher machine with an AVR. It would have a display, small lampboard, small keyboard, and even a small plugboard you could connect up with some of those flexible breadboard wires. For anyone who doesn't know what a plugboard is, it is basically 26 sockets (one for each letter of the alphabet) that you can swap with another of the 26 sockets. So you can plug A into G, O into Q with a jumper wire. Obviously if I used 26 i/o pins I could just set one to output and then read the other 25 to see if that one pin is connected to any others. That would take 26 i/o pins though. Is there another method or a matrix method that could be done to accomplish the same task with less i/o pins?