Atbash Cipher Encoder
Atbash is one of the oldest ciphers on record — used by Hebrew scribes in the book of Jeremiah around 600 BC. It maps every letter to its mirror image in the alphabet: A becomes Z, B becomes Y, and so on. Because the mapping is its own inverse, the same operation both encrypts and decrypts. It is weak by any modern standard but remains a staple of puzzles, escape rooms and introductory cryptography lessons.
How to encode with Atbash
-
1
Enter the plaintext (or ciphertext)
Letters A-Z and a-z are translated; digits, spaces and punctuation pass through unchanged.
-
2
Each letter flips to its mirror
A↔Z, B↔Y, C↔X, ... M↔N.
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3
Copy the result
The tool preserves your original case, so `Atbash` becomes `Zgyzhs`.
-
4
To decode, paste the ciphertext back in
Atbash is self-inverse: applying it twice returns the original.
The mapping
| Plain | Cipher | Plain | Cipher |
|---|---|---|---|
| A | Z | N | M |
| B | Y | O | L |
| C | X | P | K |
| D | W | Q | J |
| E | V | R | I |
| F | U | S | H |
| G | T | T | G |
| H | S | U | F |
| I | R | V | E |
| J | Q | W | D |
| K | P | X | C |
| L | O | Y | B |
| M | N | Z | A |
The name
The word atbash itself is formed from the first (aleph), last (tav), second (bet) and second-last (shin) letters of the Hebrew alphabet — a mnemonic for the flip.
Known plaintext in the Bible
The Hebrew word Sheshach (ששך) in Jeremiah 25:26 and 51:41 is widely considered an Atbash encryption of Babel (בבל) — one of the earliest documented uses of a substitution cipher.
Cryptanalytic strength: zero
Atbash is a monoalphabetic substitution with a fixed, public key. Breaking it is trivial: a five-year-old with a pencil can do it. Do not use Atbash for anything that needs to stay secret. It is fine for puzzles, clues and obfuscation where the audience knows to apply the cipher.
Frequently Asked Questions
No. ROT13 rotates each letter 13 places (A→N, B→O). Atbash reflects across the middle of the alphabet (A→Z, B→Y). Both are self-inverse. Both are trivial to break.
This tool handles ASCII A-Z/a-z. Extending Atbash to Hebrew or other alphabets is straightforward in principle but every language needs its own 26-letter-or-other mapping; non-Latin characters pass through unchanged here.
Because the mapping is symmetric. A ↔ Z means mapping A gives Z, and mapping Z gives A. Any symmetric cipher is its own inverse. The same property makes it a single-key operation with no decode mode needed.
No. Atbash is a letter substitution; digits, spaces, punctuation, emoji and accented characters all pass through untouched. That is why the ciphertext preserves word spacing and looks roughly like the plaintext.
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