How atbash cipher works
The Atbash cipher is an ancient substitution cipher that maps each letter to its reverse position in the alphabet: A becomes Z, B becomes Y, C becomes X, and so on, so the first and last letters swap, the second and second-last swap, and so forth. It was originally applied to the Hebrew alphabet and appears in biblical texts.
Because the mapping is its own inverse (Z maps back to A, Y back to B), the same operation both encrypts and decrypts — there is no separate decryption step. Only letters are affected; upper and lower case are preserved and all other characters pass through unchanged.
Atbash has no key, so it offers no real security and is trivially broken. It survives today as a puzzle, a teaching example of monoalphabetic substitution, and a cipher used in geocaching and escape-room style games. All processing happens in your browser.
Frequently asked questions
What is the Atbash cipher?
A substitution cipher that replaces each letter with the letter the same distance from the opposite end of the alphabet — A↔Z, B↔Y, C↔X. It is one of the oldest known ciphers and was originally used with the Hebrew alphabet.
How do I decrypt Atbash?
Apply Atbash again. The reverse-alphabet mapping is its own inverse, so encryption and decryption are the identical operation. Paste the ciphertext into this tool and convert to recover the plaintext.
Does Atbash have a key?
No. The substitution is fixed (A↔Z always), so there is no key to choose. This also means Atbash provides no real security — it is a historical and recreational cipher, not a way to protect data.
Are numbers and punctuation changed?
No. Only alphabetic letters are mirrored; digits, punctuation, spaces, and symbols are left exactly as they are, which preserves the structure of the original text.
