Atbash Cipher Encoder / Decoder

Atbash is one of the oldest known ciphers: it reverses the alphabet, so the first letter becomes the last, the second becomes the second-to-last, and so on. It was first used with the Hebrew alphabet — its name comes from the letter pairs aleph–tav and bet–shin — and appears in the Book of Jeremiah. This tool applies it to Latin, Hebrew and Greek letters while leaving spaces, digits and punctuation alone.

How to use this tool

1. Type or paste the text.
2. Keep all three alphabets, or limit the swap to one of them.
3. Optionally reverse the digits too.
4. Copy the result; run it again to decode.

Formula

For an alphabet of n letters numbered 0 to n − 1, letter i becomes letter n − 1 − i. Latin: A↔Z, B↔Y … M↔N. Hebrew: א↔ת, ב↔ש, ג↔ר … כ↔ל. Greek: Α↔Ω, Β↔Ψ … Μ↔Ν.

Because the mapping is a reflection, encoding and decoding are the same operation. Upper and lower case are kept; Hebrew and Greek final forms are treated as their base letters.

Example

HELLO becomes SVOOL: H (8th letter) ↔ S (8th from the end), E ↔ V, L ↔ O. In Hebrew, בבל (Babel) becomes ששכ, written ששך with a final kaf — the "Sheshach" of Jeremiah 25:26.