Is the reverse alphabet cipher the same as Atbash?

Yes. Atbash, originally an ancient Hebrew cipher, maps each letter to the one at the mirror position in the alphabet: A to Z, B to Y, and so on. This tool builds that mapping explicitly for the Latin alphabet, so the two are identical for English text.

Why is it its own inverse?

Mirroring twice returns to the start. If A maps to Z, then applying the same rule to Z maps it back to A. So encoding and decoding are the exact same operation and you do not need a separate decode mode.

Does it handle case and punctuation?

Yes. Uppercase stays uppercase and lowercase stays lowercase after mirroring, and any non-letter such as a space, digit, or symbol passes through unchanged.

What is the formula for each letter?

For a zero-based letter index i from 0 to 25, the mirrored index is 25 minus i. Equivalently, the new character code is 90 minus (code minus 65) for uppercase, or 122 minus (code minus 97) for lowercase.

No. It is a fixed monoalphabetic substitution with no key, so anyone who recognises the pattern can reverse it instantly. It is useful for puzzles, light obfuscation, and teaching the idea of substitution.

What is the Reverse Alphabet Cipher?

Substitutes each letter with the letter at the mirror position in a reversed alphabet, so A becomes Z, B becomes Y, and so on. This is the Atbash cipher constructed explicitly, and it is its own inverse. Runs in your browser. It runs free in your browser on Gera Tools, with nothing uploaded.

Reverse Alphabet Cipher

Name: Reverse Alphabet Cipher
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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The reverse alphabet cipher replaces every letter with the letter the same distance from the opposite end of the alphabet — A with Z, B with Y, C with X, and so on. It is the Atbash cipher written out as an explicit reversed alphabet, and because mirroring is symmetric it is its own inverse.

How it works

Treat each letter as a zero-based index (A=0 … Z=25) and subtract it from 25 to find its mirror:

plain    = 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
reversed = 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
index i  -> mirror 25 - i

For uppercase letters the new code is 90 - (code - 65), and for lowercase it is 122 - (code - 97). Non-letters are left untouched.

The self-inverse property explained

The most interesting property of this cipher — and the one that makes it particularly clean to implement — is that encoding and decoding are identical operations. This happens because the underlying mapping is a perfect mirror: if A maps to Z, then Z must map to A. If you apply the same rule twice, you return to where you started.

This means you do not need a “decode” mode. Run the ciphertext through the same tool and you get plaintext. Compare this to a Caesar cipher, where encoding with a shift of 3 requires decoding with a shift of negative 3, or with a Vigenère cipher where you need the original key to reverse. Atbash has no key at all — the mapping is fixed and fully public.

Brief history

The Atbash cipher is one of the oldest known cipher systems. It appears in the Hebrew Bible, where scribes used it to substitute letters in the Hebrew alphabet. The word “Atbash” itself is formed from the first and last two letters of the Hebrew alphabet in the same way “ABC” names the English one. The same principle applied to the Latin alphabet produces the tool you see here.

Example and notes

HELLO becomes SVOOL, and running SVOOL back through the tool returns HELLO — no separate decode step is needed.

A few more examples:

Plain	Cipher
HELLO	SVOOL
SECRET	HVXIVG
ABCXYZ	ZYXCBA
Hello World	Svool Dliow

Punctuation, spaces, and digits pass through unchanged. Case is preserved: a lowercase a becomes a lowercase z, not an uppercase Z.

Because there is no key and the mapping never changes, the reverse alphabet cipher offers no real secrecy against anyone who recognises the pattern. It is well-suited for hiding answers in puzzles, light obfuscation of text, or teaching the foundational concept of a monoalphabetic substitution cipher.