Cipher Engine — Julius Caesar, 58 BC

The Art of Hidden Words

Transform any message into an uncrackable code using the world's oldest and most elegant substitution cipher. Shift every letter by a secret number — simple, powerful, timeless.

26 possible keys Symmetric cipher Letter substitution
13
shift
/ 01 — Cipher Engine
Encode & Decode
Shift
13
Encoded message appears here
/ 02 — Cipher Key
The Substitution Key
Shift = 13
/ 03 — How It Works
1 ✍️
Write your message

Type any text — letters, words, sentences. The cipher works on every alphabetic character while leaving spaces and punctuation untouched.

2 🔢
Choose your shift

Pick a number from 1 to 25. This is your secret key. Each letter is replaced by the letter that sits N positions ahead in the alphabet.

3 🔐
Send the cipher

Share your encoded message. Only someone who knows the shift value can decode it — sliding each letter back by the same number to reveal the original.

/ 04 — By The Numbers
58 BC First recorded use
ROT13 Most famous variant
25 Possible key values
26 Letters in cipher
∞ Messages encodable