Classical Cipher Tool: Caesar, ROT13, Vigenere & Atbash
Encrypt or decrypt text with the Caesar cipher, ROT13, ROT47, Vigenere cipher, or Atbash. If you do not know a Caesar shift, the brute-force list shows all 25 candidates at once. Classical ciphers are for puzzles, learning, and fun, and they are not secure. For real encryption, use the Text Encryptor & Decryptor (AES); for plain encoding, try the Base64 Encoder/Decoder.
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Brute force (all 25 shifts)
Your input decrypted with every shift from 1 to 25. The row that reads as real text shows the shift that was used.
How to use
- Choose a cipher. For Caesar, set the shift; for Vigenere, enter a key.
- Choose Encrypt or Decrypt, then enter your text.
- Check the result and copy it. If the shift is unknown, scan the brute-force list below.
Notes
- Every classical cipher here is trivial to break today. Do not use them to protect passwords or personal data; use a modern cipher such as AES-GCM for real encryption.
- The Caesar, ROT13, Vigenere, and Atbash ciphers only change English letters (A-Z, a-z). Digits, symbols, and non-Latin text pass through unchanged, and letter case is preserved.
- ROT47 works on all printable ASCII characters (! to ~), so digits and symbols change too. ROT13, ROT47, and Atbash are their own inverse: encrypting and decrypting are the same operation.
- Only letters in the Vigenere key are used, and the key does not advance on non-letter characters such as spaces or punctuation.
Glossary
Caesar cipher
A substitution cipher that shifts every letter a fixed number of places along the alphabet. The shift is the key, and with only 25 possibilities it is broken instantly by brute force.
ROT13
A Caesar cipher with a shift of 13. Because the alphabet has 26 letters, applying it twice returns the original text. It is used for light obfuscation such as hiding spoilers.
Vigenere cipher
A polyalphabetic cipher that uses each letter of a keyword as the shift for the matching position, switching between Caesar shifts. It is harder to break than a single Caesar shift, but still not secure today.
Atbash cipher
A cipher that maps the alphabet onto its reverse (A becomes Z, B becomes Y). It has no key, and encrypting and decrypting are the same operation.
FAQ
How do I crack a Caesar cipher when I do not know the shift?
Choose the Caesar cipher and paste the text: the brute-force list shows the input decrypted with all 25 shifts. The row that reads as real text is the answer, and its shift is the key. With only 25 candidates, it takes seconds even by eye.
What does ROT13 do to digits and non-English text?
ROT13 rotates only the English letters A-Z and a-z by 13. Digits, symbols, and Japanese or other non-Latin characters are left as they are. ROT47 also rotates digits and symbols across printable ASCII (! to ~), but non-ASCII text is still untouched.
What happens if a Vigenere key contains digits or symbols?
Only the letters A-Z in the key are used (case does not matter); digits, symbols, and spaces are ignored. A key with no letters at all shows an error. Also note that the key does not advance on spaces or punctuation in your text, so results can differ from tools that count every character.
Can a classical cipher protect passwords or personal data?
No. The Caesar, ROT13, Vigenere, and Atbash ciphers can be broken in seconds today. Use them for puzzles, learning, or hiding spoilers, and use a modern AES-based encryptor when you need real protection.
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