Atbash Cipher

Encode and decode text with the Atbash mirror cipher (A↔Z, B↔Y)

What is it and how does it work?

The Atbash cipher is one of the oldest known substitution ciphers, originating in ancient Hebrew tradition around 600 BC. It works by reversing the alphabet: A becomes Z, B becomes Y, C becomes X, and so on through to Z becoming A. The name "Atbash" comes from the Hebrew letters: Aleph (א) → Tav (ת), Bet (ב) → Shin (ש) — the first and last, second and second-to-last Hebrew letters. The critical property of Atbash is that it is its own inverse: applying Atbash to ciphertext produces the original plaintext — encrypt and decrypt are the same operation.

Atbash appears in the Hebrew Bible — the Book of Jeremiah uses it to encode the word "Babel" as "Sheshach" (שׁשׁך) and "Chaldea" as "Lev-Kamai". Despite its historical significance, Atbash provides zero security by modern standards: with only one possible key (the full alphabet reversal), it requires no analysis to crack. This tool applies Atbash to text in any supported alphabet: Latin, Hebrew, Greek, Cyrillic, or Arabic.

Common use cases

• Historical decoding: decode "Sheshach" (שׁשׁך) from the Book of Jeremiah back to "Babel" (בבל) using Hebrew Atbash — one of the earliest documented uses of encryption in literature.
• Puzzle design: use Atbash as a layer in a multi-cipher puzzle — its self-reciprocal property (same operation to encode and decode) makes it elegant for escape room challenges.
• Alphabet learning: apply Atbash to a word and challenge learners to identify the letter pairs — good for teaching alphabet positions and reversal patterns.

Frequently asked questions

Why is Atbash cipher its own inverse?

Atbash maps each letter at position i to the letter at position (n−1−i) where n is the alphabet size. Applying Atbash again maps position (n−1−i) back to position n−1−(n−1−i) = i — the original position. This is the mathematical property of an involution: a function that is its own inverse. The same property holds for ROT13 (a Caesar cipher with shift 13 in a 26-letter alphabet) — both are symmetric self-inverse operations.

How does Atbash differ from other simple ciphers?

Caesar cipher shifts the alphabet by a fixed amount (A→D, B→E with shift 3). Atbash reverses the alphabet (A→Z, B→Y). ROT13 is a Caesar cipher with shift 13. All three are monoalphabetic substitution ciphers — each plaintext letter always maps to the same ciphertext letter. They all have the same weakness: frequency analysis instantly breaks them. The difference is the specific mapping: Atbash has exactly 1 key; Caesar has 25 possible keys; Atbash is a special case where the key happens to be the full reversal.

What is the Atbash cipher for Hebrew?

Hebrew Atbash maps: א (Aleph)↔ת (Tav), ב (Bet)↔ש (Shin), ג (Gimel)↔ר (Resh), ד (Dalet)↔ק (Qof), ה (He)↔צ (Tsadi), ו (Vav)↔פ (Pe), ז (Zayin)↔ע (Ayin), ח (Het)↔ס (Samekh), ט (Tet)↔נ (Nun), י (Yod)↔מ (Mem), כ (Kaf)↔ל (Lamed). The name Atbash itself encodes this: Aleph-Tav-Bet-Shin = the first two pairs of the cipher.

Is Atbash cipher used anywhere today?

Atbash appears in: occult and esoteric traditions (Kabbalah uses Atbash for mystical letter substitutions), puzzle games and escape rooms (its self-inverse property is useful), historical fiction and games set in ancient periods, and occasionally as a simple teaching example in cryptography courses. It has no practical security use — it's trivially broken by inspection since the mapping is fixed and universally known.

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