Class Openers

Class Opener – Day 52 – “Impossible” Codebreaking

It’s day 3 of codebreaking openers, and time to up the ante! After offering Jolly Ranchers (who should provide me stock, with all the great pub I give them in my classroom) and candy bars for codebreaking challenges, we’re ready for the big time….


And BOOM goes the dynamite!

“That’s a filthy lie!”

Wait…do my students not trust me? Well, I suppose my students have good reason to NOT trust me, as it’s not everyday practice to hand out gift cards for solving problems.  But the cell phones came out, typing in the phrase with faint hopes of Googling an answer.  Many students had questions about yesterday’s code – a Hill cipher – wanting to know how letters become numbers, and great questions about the role of inverses. And while I gave very few clues about today’s challenge, I assured them that it was NOT done with a Hill cipher – something much more complex is going on.


I was feeling a little generous (just a little), and left a small clue on a side board for them to consider. But just how helpful is it?  What are rotors? And what’s with the Roman numerals?  Just a small clue that today’s challenge was coded using an Engima machine – or at least an online applet simulation of one. This is a challenge I have done before, and for the last 12 years, and have yet to give out a gift card.  This is the first year I have given out at least a little information – rotor positions – and I am still supremely confident that my message will not be broken.

I’m giving away some of the explanation, but I am not worried – unless my students are REALLY persistent. While classwork was done today, many students had great questions about the problem, finding ideas on their phones (which I endorse!).  And I admit I started to get a little nervous when I saw a photo of an Enigma machine on one phone.  Am I tempting fate?  We’ll find out by tomorrow.


By Bob Lochel

HS Math Teacher. Hatboro-Horsham School District, Horsham, PA.

2 replies on “Class Opener – Day 52 – “Impossible” Codebreaking”

I just explained the process to them, so the contest is now closed. And now, for 12 consecutive years, I have not given away a gift card. But I feel like I am tempting fate with the improvement of technology.

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