Classical Ciphers
Encrypt and decrypt text with seven historical ciphers — Caesar, Vigenère and more.
How many positions each letter moves along the alphabet — 3 was the shift Julius Caesar himself is said to have used.
What are classical ciphers
Classical ciphers are the encryption methods used before computers — from simple substitutions in the Roman Empire to pen-and-paper ciphers of the early 20th century. All of them were broken long ago, some in minutes with just paper and pencil, but they remain the best entry point for understanding the concepts behind modern cryptography: key, substitution, transposition, and what actually makes a method secure.
How it works: Caesar
Every letter of the text is shifted a fixed number of positions along the alphabet — with shift 3, A becomes D, B becomes E, and so on, wrapping back to the start after Z. Decrypting just shifts in the opposite direction.
History: Caesar
According to the Roman historian Suetonius, Julius Caesar used this shift (with value 3) to correspond with his generals, reasoning that an enemy intercepting the message wouldn't know where to even start reading it. With only 25 possible shifts, it's broken in seconds today — by trying all of them at once, exactly what this page's brute-force mode shows.
Frequently asked questions
No. Every one of them was broken centuries or decades ago and exists here purely for education, recreation (CTF, geocaching, escape rooms) or historical curiosity. To protect a real secret, use the Encrypt/Decrypt tool (AES-256).
Every classical cipher here operates on the 26-letter A-Z alphabet — the same alphabet used in the original historical examples. Any character outside it (accented letter, punctuation, digit, space) passes through unchanged, and decrypting always returns the text exactly as typed.
No — every encryption/decryption happens in your browser. No text, key, or result ever leaves your computer.
Every language has letters that appear more often than others (in English, E and T are the most common). In a substitution cipher, that distribution survives encryption — only the letters' labels change, not the proportions. Comparing the ciphertext's chart against the reference distributions is how a cryptanalyst figures out where to start breaking the cipher.
With only 25 possible shifts (26 minus shift 0, which wouldn't encrypt anything), it's faster to generate all of them and read which one makes sense than to guess one at a time — exactly how a computer (or a patient person) would break this cipher in practice.
Yes — that's one of the audiences this tool has in mind. Caesar's brute-force mode and the Substitution/Vigenère frequency chart were designed to help crack a puzzle, not just to encrypt one.