Caesar & Substitution
📋 What it is
A Caesar cipher shifts each letter a fixed amount; a substitution cipher swaps each letter for another by a fixed map.
🗣️ Coach says
The Caesar cipher shifts every letter the same number (shift 3: A→D). A substitution cipher is more general — each letter maps to another by a secret table. Both share one idea: a CONSISTENT rule you reverse to decode.
🧠 Memory hook
Caesar = shift every letter the same amount. Reverse the shift to decode.
😂 Giggle
What do you call a spy who sleeps under a blanket?
An undercover agent!
😲 Whoa!
Julius Caesar really used a shift-of-3 cipher for military orders 2,000 years ago — which is why the whole family of shift ciphers is named after him.
✅ Quick check: With a Caesar shift of 3 (A→D), decode “KHOOR”.
Say your answer out loud first — then reveal.
“HELLO” — shift each letter back by 3: K→H, H→E, O→L, O→L, R→O.
Reversing the fixed shift decodes each letter exactly.
🪄 Trick question: If you don’t know a Caesar cipher’s shift, is it unbreakable?
Careful — think it through, then reveal.
No — there are only 25 shifts, so you can try them all (brute force) until it reads. Small keys are weak.
A tiny key space means every option can be tested.
🧪 Try it! (2 minutes)
Encode your name with a shift-of-5 cipher, then have a friend decode it with the key “5”.