Atbash cipher online – encoder/decoder
Atbash cipher encoder and decoder online: reverse the alphabet so A becomes Z. Use the full table, a REBUS → IVYFH example and no key.
A cipher hidden in the pages of the Bible
What is the Atbash cipher?
Atbash is a substitution cipher that reverses the alphabet: the first letter becomes the last, the second becomes the second to last, and so on. The method has no key — the only secret is the fact that this particular substitution was used.
How does the mirrored alphabet work?
Write the alphabet from A to Z and, underneath, the same alphabet backwards. Each letter in the top row becomes the letter directly below it: A becomes Z, B becomes Y, M becomes N. The tool works with the 26-letter Latin alphabet.
Example with the word REBUS
The message “REBUS” turns into “IVYFH”: R→I, E→V, B→Y, U→F and S→H. Applying Atbash to the result restores the word “REBUS”. You can reproduce this example with the working tool above.
Complete mirrored alphabet table
The rows read in both directions: a letter on top becomes the letter beneath it, and the same pair works the other way round. In the middle of the alphabet M and N point at each other.
| Plaintext | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Ciphertext | Z | Y | X | W | V | U | T | S | R | Q | P | O | N | M | L | K | J | I | H | G | F | E | D | C | B | A |
How do you decrypt the text?
Decryption needs no separate operation. The substitution is reciprocal, so the same step turns plaintext into ciphertext and ciphertext back into plaintext. Simply run the message through the tool again.
Atbash and the Caesar cipher
Caesar slides the whole alphabet by a chosen number of places, while Atbash flips it, so the distance between a plaintext letter and its replacement differs every time. Atbash has nothing to configure: only one substitution exists, whereas Caesar offers 25 different shifts.
See also: Caesar cipher
How can the Atbash cipher be broken?
Nothing has to be guessed — recognising the method and repeating the substitution is enough. The look of the text often gives it away: a frequent E becomes V and A becomes Z. In longer messages letter-frequency analysis reveals the method as well.
Why is the Atbash cipher insecure?
The cipher has no key space: anyone who knows the rule reads the message immediately. The structure of the text survives untouched — word lengths, repeated letters and language patterns all remain visible. Treat Atbash as a puzzle and an exercise, not as protection.
History of the Atbash cipher
Atbash comes from the Hebrew tradition and its name joins the letters aleph–tav and bet–shin, that is the first with the last and the second with the second to last. A classic example appears in the Book of Jeremiah, where the name “Sheshach” is read as Babel. The Latin version used by the tool is a later adaptation of the rule to a 26-letter alphabet.
Atbash alphabet to print
An A4 worksheet with the reversed alphabet, a worked example, a puzzle and blank fields for practising the cipher.