Shift-alphabet wheel
Apply and reverse one fixed wraparound letter substitution.
Adult planning suggestion: about9–12 · Language & storytelling
- Players
- 2–3 per group
- Time
- 12–20 minutes
- Materials
- Two A–Z strips, shift label+3 and message log.
Prepare
Align plain alphabet A–Z with shifted alphabet D–Z,A,B,C. Label the direction plain→cipher and key+3. This activity transforms uppercase Latin letters only; preserve spaces and punctuation. In the Chinese guide use the supplied Latin-letter examples rather than pretending to rotate Chinese characters.
Play
For each plaintext letter find its position on the plain strip and copy the letter underneath. The same mapping applies every time. To decode, find the ciphertext on the shifted strip and read above. Do not add another three when decoding. Rotate sender, receiver and checker after each short message.
Worked example
CAMP becomes FDPS. XYZ becomes ABC by wraparound. Decoding ABC gives XYZ, not DEF. A correct round trip restores every original letter and space; simply producing a word that looks plausible is not enough to verify the direction.
Finish and check
Exchange two messages and compare the decoded text with the original after reveal. Count a corrected mismatch as a successful repair, not a penalty. If changing the key, relabel both strips before another message and use a fresh check. Stop after everyone has decoded once.
Adaptation and limits
Use large strips or a partner scribe. This historical-style substitution is easy to break and is not suitable for passwords, private information or real security. The technical source supports the cipher idea; the strips and examples are independently prepared.
Purpose, observation and provenance
Within this activity: Apply and reverse one fixed wraparound letter substitution.
Ask the learner to state the mapping direction and reverse a wraparound example.
Our rules, examples and printable diagrams are separately prepared. The earliest inventor of the broader mechanism is not established here.
Computer Science Field Guide — Substitution ciphers — Technical Caesar-substitution background; our strips and classroom examples are original.
Age bands are planning suggestions. Goals describe observable actions, not measured long-term gains or institutional endorsement.
Free alternative: Copy the supplied grids, labels and cards onto reused paper. No specialist product is needed. Adults may prepare pieces or act as a scribe.
Printable materials
Preview at 100% scale, with browser headers and footers off. Cut with suitable help. Keep host keys separate. This is a manual tabletop kit, not an online opponent, automatic judge or solver.
Player materials · Shift-alphabet wheel
Plain ABCDEFGHIJKLMNOPQRSTUVWXYZ
Cipher DEFGHIJKLMNOPQRSTUVWXYZABC
Encode CAMP and XYZ; decode ABC.
| Plain | Cipher+3 | Plain | Cipher+3 |
|---|---|---|---|
| A | D | N | Q |
| B | E | O | R |
| C | F | P | S |
| D | G | Q | T |
| E | H | R | U |
| F | I | S | V |
| G | J | T | W |
| H | K | U | X |
| I | L | V | Y |
| J | M | W | Z |
| K | N | X | A |
| L | O | Y | B |
| M | P | Z | C |
Player record · keep host key separate
| Message | Direction/key | Result |
|---|---|---|
| ________ | ________ | ________ |
| ________ | ________ | ________ |
| ________ | ________ | ________ |
| ________ | ________ | ________ |
| ________ | ________ | ________ |
| ________ | ________ | ________ |
| ________ | ________ | ________ |
| ________ | ________ | ________ |
Host key · separate from players
CAMP→FDPS; XYZ→ABC; ABC decoded→XYZ. Spaces stay unchanged.
Run the round
Align plain alphabet A–Z with shifted alphabet D–Z,A,B,C. Label the direction plain→cipher and key+3. This activity transforms uppercase Latin letters only; preserve spaces and punctuation. In the Chinese guide use the supplied Latin-letter examples rather than pretending to rotate Chinese characters.
For each plaintext letter find its position on the plain strip and copy the letter underneath. The same mapping applies every time. To decode, find the ciphertext on the shifted strip and read above. Do not add another three when decoding. Rotate sender, receiver and checker after each short message.
CAMP becomes FDPS. XYZ becomes ABC by wraparound. Decoding ABC gives XYZ, not DEF. A correct round trip restores every original letter and space; simply producing a word that looks plausible is not enough to verify the direction.
Exchange two messages and compare the decoded text with the original after reveal. Count a corrected mismatch as a successful repair, not a penalty. If changing the key, relabel both strips before another message and use a fresh check. Stop after everyone has decoded once.
Use large strips or a partner scribe. This historical-style substitution is easy to break and is not suitable for passwords, private information or real security. The technical source supports the cipher idea; the strips and examples are independently prepared.