SUNY Geneseo Department of Mathematics
Friday, October 29
INTD 105 17
Fall 2021
Prof. Doug Baldwin
(No.)
Try to get a sense of what actually using an Enigma machine would have been like, especially some of the issues surrounding how to fit the machine into a larger communication problem.
Enigma was used to protect radio communications in the German military. The problem with radio is that it’s a broadcast form of communication, i.e., anyone with a radio receiver can hear what other people send. We’ll simulate that by “broadcasting” messages in a shared, projected, Google doc.
In order to have someone to communicate with, pick a person or small group somewhere else in the classroom as a “partner.” Your goal is to use Enigma encryption to send them messages through the “broadcast” Google doc without anyone else knowing what you’re saying.
To encrypt and decrypt with Enigma, use the simulator at
https://www.101computing.net/enigma-machine-emulator/
To send a message, use the simulator to encrypt it, then type the encrypted message into the Google doc. To read a message, copy it from the Google doc to the simulator. Try to resist the urge to use copy and paste in this, since actual Enigma operators didn’t have copy and paste between the Enigma machines and their radios.
Things we noticed while doing this exercise:
There’s a very low tolerance for error. Typos either have to be accepted, or require restarting the entire message. Even worse, small mistakes in setting up an Enigma can make a message completely indecipherable to its recipient.
Small things in how you use Enigma make a difference. For example, inserting spaces between ciphertext words gives cryptanalysts a big clue about your message, whereas just sending in uniform groups of 4 letters (as was actually done) eliminates that clue but assumes that recipients can guess where word boundaries are.
Some amount of communication between parties is inevitably unencrypted. In our example that included things like requests to put messages in a particular place so the recipient would recognize that the message was for them; in actual use it included things like call signs to identify sender and receiver.
Start talking about Alan Turing, one of the key figures at Bletchley Park, although one we haven’t learned much about yet.
Please read Act 1 of “Breaking the Code” for Monday.