The KIM Uno is capable of displaying 4 hexadecimal digits on the left and two hexadecimal digits on the right. Below it has a hexadecimal keyboard as well as 8 control keys.

This got me thinking. The four digits can represent rotors in an encrypting machine and the two digits on the right can represent the input number and the encrypted version.

The keys below the display can be used to move the rotors. The first row of keys [GO] [ST] [RS] [SST] cannot be used because the ST and RS keys stop a running program and resets the CPU respectively.

The [AD] [DA] [PC] [+] keys have no effect on a running program and can be read. The same situation applies to the row below [C] [D] [E] [F}.

So, we will use [AD]/[C] to increment/decrement the leftmost rotor value. [DA]/[D], [PC]/[E] and [+]/[F] to alter the remaining rotors.

Pressing a 0..9 key will encrypt it and [A] and [B] will be unused for the moment.