Atbash Cipher — Reverse-Alphabet Substitution (Self-Inverse)
Encode/decode Atbash cipher: A↔Z, B↔Y, etc. Self-inverse. Hebrew origin. Free, in-browser, no signup.
About Atbash Cipher
The Atbash cipher is one of the oldest known substitution ciphers — originally used in Hebrew (Aleph ↔ Tav, Beth ↔ Shin) and adapted to any alphabet — that maps each letter to its mirror across the alphabet (A ↔ Z, B ↔ Y, ..., M ↔ N). Like ROT13, it is self-inverse: applying Atbash twice returns the original. The ZTools Atbash tool encodes and decodes Latin (English), Hebrew, and Greek alphabets, preserves case, passes non-letters through unchanged, and is suitable for educational demos, puzzles, and casual obfuscation — never for real security.
Use cases
- Religious / historical study. Atbash appears in the Hebrew Bible (Jeremiah uses "Sheshach" as Atbash for Babel). Demonstrate the cipher for Bible-study or history classes.
- Cryptography 101. Teaching substitution ciphers — Atbash is even simpler than Caesar (no shift parameter to choose). One mapping, fixed.
- Puzzles and escape rooms. Hide a clue with Atbash. Solvers decode without needing a key beyond the alphabet itself.
- Hidden spoilers / jokes. Lighter than ROT13 in some communities; same purpose: read only if you choose to decode.
How it works
- Pick alphabet. Latin (A–Z), Hebrew (22 letters), Greek (24 letters).
- Paste text. Text in the chosen alphabet. Other characters pass through.
- Apply Atbash. Each letter maps to its mirror (1st ↔ last, 2nd ↔ second-to-last, etc.).
- Inspect. Side-by-side original / encoded view.
- Decode. Apply Atbash again — self-inverse, so the same operation undoes it.
Examples
Input: HELLO
Output: SVOOL
Input: SVOOL
Output: HELLO (self-inverse)
Input: BABEL → Hebrew Atbash
Output: SHESHACH (Biblical reference: Jeremiah 25:26)
Frequently asked questions
How is Atbash different from Caesar?
Caesar shifts every letter by the same number (configurable 1–25). Atbash mirrors the alphabet — no parameter, fixed mapping. Caesar with shift = 25 looks similar but is not the same; only the symmetric mirror is "Atbash".
Why is it self-inverse?
Because mirroring twice returns the original position. If A → Z then Z → A; both operations use the same rule.
Is Atbash secure?
No — trivially broken by frequency analysis or guessing once you suspect it. Use only for fun and education.
Does it work on lowercase?
Yes — case is preserved. "hello" → "svool".
What about Hebrew or Greek?
Yes — the tool supports both. Hebrew Atbash maps Aleph ↔ Tav. Greek maps Alpha ↔ Omega. Same self-inverse property.
Will it handle accented letters (é, ñ)?
No — they pass through unchanged. Atbash is defined only on the chosen base alphabet.
Pro tips
- For puzzles, pair Atbash with another step — alone it is too easy.
- For Bible study, demonstrate the Sheshach example — a memorable real-world appearance.
- For mixed alphabets, run each segment through its corresponding alphabet setting.
- Use sparingly — once readers know the cipher, decoding takes seconds.
- For real obfuscation, pair with Caesar at a non-13 shift; combinations are slightly more puzzle-friendly.
Reviewed by Ahsan Mahmood · Last updated 2026-05-05 · Part of ZTools.
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