🔡Security

Atbash Cipher Decoder

Decode and create messages in the Atbash cipher, which swaps each letter for its opposite in the alphabet (A↔Z, B↔Y). Shows the full map and the result.

Text

Decodificado

—

Atbash: the alphabet read backwards

Atbash swaps each letter for its mirror in the alphabet: A becomes Z, B becomes Y, C becomes X and so on to the middle, where the process reflects. The name comes from the Hebrew letters aleph, tav, bet and shin, the first two pairs of that swap — the cipher appears in biblical texts, where some proper names are written in this form.

Paste the text and the page converts it, showing the start of the correspondence map. There is no key and no direction option, and that is not a limitation: the cipher is its own inverse. Applying Atbash to already-enciphered text returns the original, because the alphabet's symmetry undoes itself when applied twice.

As protection it is worth nothing — there is no key, so anyone who recognises the method reads straight through. What makes it interesting is something else: it is the oldest documented example of a substitution cipher, some two and a half thousand years old, and it shows that the idea of systematically swapping one letter for another long predates any mathematical concern with security.

Frequently asked questions

Why does applying it twice return the original?

Because the swap is symmetric: if A becomes Z, then Z becomes A. Each pair trades mutually, and no letter lands anywhere other than where its partner came from. Ciphers with that property are called involutions — ROT13 is another example.

Does it really appear in the Bible?

Some passages in the book of Jeremiah contain the word Sheshach, which in Hebrew Atbash corresponds to Babel. The most accepted reading is that this was political discretion rather than cryptographic secrecy — the text would be recognisable to anyone who knew the convention.

Is there a version for the 26-letter alphabet?

That is precisely this one. The original Atbash operates on the 22 letters of the Hebrew alphabet; the adaptation to the Latin alphabet applies the same mirroring rule across 26 letters. The idea is identical, only the mapping changes with alphabet size.

Related Tools

🔐

Encrypt Text

Apply classic ciphers (Caesar, ROT13, Atbash) or Base64. Useful for puzzles, CTFs and testing — do not use for real security.

🪞

Atbash Cipher

Apply the Atbash cipher (A↔Z, B↔Y, C↔X...): each letter is mirrored in the alphabet. Ancient Hebrew cipher used in the Bible. Applying twice returns the original. Everything in your browser.

🏛️

Caesar Cipher Brute-Force (All 25 Shifts)

Crack a Caesar cipher by showing all 25 possible shifts at once. Great for breaking coded messages, puzzle games and studying cryptography.

🗝️

Columnar Transposition Cipher

Encrypts or decrypts text by writing it in rows under a keyword and reading the columns in alphabetical key order, padding the last row with X.

🔐

Vigenère Autokey Cipher Encoder and Decoder

Enciphers or deciphers text with the classic autokey variant, where the plaintext extends the keyword instead of repeating it. Letters A to Z only.

🥓

Baconian Cipher, 5-Bit A/B Groups

Encodes each letter as a group of five A and B symbols in Bacon's 24-letter alphabet, where I shares a code with J and U shares one with V.