Cipher Challenge: teacher guide

📘 In short

Eight codebreaking challenges tell one story, set in the city of Aurora in 2084. Each challenge teaches one idea and has three steps:

Begin with Briefing 0: Introduction, which sets out the story and how the challenge works.

🖨 Printable pack📽 Briefing 0👩‍🏫 Class codes and solutions🧰 Toolkit

✏️ Paper first, tools for help and checking

The challenge works best when students crack the messages on paper, in pencil: spotting patterns, counting letters and testing guesses is where the thinking happens, and pairs talk more over a shared sheet than over a screen.

• Print the challenges and resources before each session from the printable pack: each message prints with a line under every letter and a frequency table to fill in, and the pack has a cipher wheel to cut out (two discs and a split pin) and a Vigenère square. Every challenge page also has its own 🖨 Print button.
• Use the online tools for help: the shift wheel, letter counts, the letter swap board, the alphabet maker (it can find an affine key from two guessed letters), rearranging for transpositions, keyword shifts for Vigenère, and a word finder for words with a given pattern.
• Use the site to check: once every letter is filled in online, ✔ Check my answer says whether the whole message is right, and then shows it properly written out. It never says how many letters are right, so it can’t be used to guess the answer letter by letter.
• 💡 Hints: three per message, from a nudge to the method. You can see who used them.

The later challenges (Vigenère, Challenges 7 and 8) need a lot of counting: let students use the online tools for the counting, and keep the reasoning on paper.

🕐 A typical session (about an hour)

Eight challenges plus the introduction fill about a term at one session a week. Part B messages are good for students to carry on with between sessions.

👥 Class codes (optional)

On Class codes, make a code for your group. Students join at mrwellsmaths.com/join (like every class activity) with the code and their first name and the first letter of their surname; their work is saved as they go, and joining with the same name on another device carries on where they left off.

• Open the challenges one at a time, so the class stays together and nobody reads ahead in the story.
• 📝 Paper only: tick it and students in the class see no coded message or tools on screen at first, so they can’t just turn the wheel until it works. They crack the message on the printed sheet, then press “I’ve cracked it on paper: I’m ready”: the message and the tools appear, and they set the wheel (or the key) to what they worked out and press Fill, or fill in the letter table, and it is checked at once. Right: well done, on to Part B. Wrong: “That doesn’t work”, the message and tools hide again, and they go back to their sheet. Untick it whenever you want them to have the tools again.
• See each student’s progress: the % of letters right so far, ✅ when solved, and hints used. Press a box to see their work letter by letter, with wrong letters in red.
• 🔑 Solutions: every message’s key and plain text, which you can print.
• 🖥 Present shows a leaderboard on the board, with no answers.

🧮 The maths in it