Each Vigenère question supplies a repeating key, so you can focus on lining it up and subtracting the right shifts. Sets use short keys such as LEMON, MAP, STAR, and CLOUD. Keep each key beside its question as you work.
Write the key row first
Write the repeated key under the message letters before calculating. Leave spaces without a key letter and keep the sequence going across words. This makes it much easier to spot a key that has slipped by one position.
Sample with a short key
HELLOKey MAP; printed ciphertext TEAXOTEAXO| Row | Value |
|---|---|
| Ciphertext | TEAXO |
| Repeated key | MAPMA |
| Plaintext | HELLO |
What to do
- Label the alphabet A = 0 through Z = 25.
- Subtract the matching key index from each ciphertext index.
- Wrap negative results into 0–25.
- Read the resulting letters and encode them again with the same key.
For the third letter, A = 0 uses key P = 15. Subtract to get −15, then wrap around to 11, or L. A negative result along the way is normal; adding 26 brings it back into the alphabet.
A quick extra question
Encode MAP using the one-letter key B.
Keep the work visible
Leave space for a key row and the letter positions used in the calculation. If an answer looks nearly right, compare the key alignment first. Restarting the key at a new word is an easy mistake to miss.
Make a known-key practice set
Set a seed and question count, then generate the Vigenère sheet. Record the seed, worksheet type, count, and generator version to get the same questions again. Both A4 and Letter are available, with an optional answer key that starts on its own pages.