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Atbash Cipher

Tool to decrypt/encrypt with Atbash (Mirror code), a substitution cipher replacing the first letter of the alphabet with the last, the second with the penultimate etc.

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Atbash Cipher -

Tag(s) : Substitution Cipher

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# Atbash Cipher

## Atbash Encoder

### What is Atbash cipher (Definition)

Atbash cipher (also called mirror cipher or backwards alphabet or reverse alphabet) is the name given to a monoalphabetical substitution cipher which owes its name and origins to the Hebrew alphabet.

### How to encrypt using Atbash cipher

Atbash encryption uses a substitution alphabet and its reciprocal, a combination of the normal alphabet and its reverse alphabet (mirrored).

Example: The latin alphabet ABCDEFGHIJKLMNOPQRSTUVWXYZ and its reverse: ZYXWVUTSRQPONMLKJIHGFEDCBA are combine in the substitution table:

 Normal ABCDEFGHIJKLMNOPQRSTUVWXYZ Reverse ZYXWVUTSRQPONMLKJIHGFEDCBA

Encryption consists in replacing letters from the first with letters from the other one, with is equivalent to replace the first letter of the alphabet A with the last one Z, the second one B with the penultimate Y etc.

Example: MIRROR becomes NRIILI

### How to decrypt Atbash cipher

Decryption is identical to encryption because of the reversible alphabet (due to the symmetry of the backwards alphabet)

Example: ZGYZHS is decrypted ATBASH

dCode offers an encoder and a decoder, but they are actually one and the same Atbash converter.

### How to recognize an Atbash ciphertext?

An Atbash ciphertext has a coincidence index similar to an unencrypted text.

If the encryption used the classical latin alphabet, letters V,G,R,L,M appear the most frequently.

Otherwise the presence of Hebrew characters or a reference to the Dead Sea can be a clue.

The notions of mirror, reflection, opposite, axis, direction, word written in reverse (hsabta) are also clues.

### Why is this cipher called 'Atbash'?

In the Hebraic alphabet, aleph (first letter) was replaced by tav (last letter) and beth (second letter) with shin (second last), etc. Initials make A,T,B,SH.

### What are Atbash variants?

Atbash is adaptable to any alphabet, so using the Hebrew alphabet is possible.

The atbash cipher is equivalent to an affine cipher with $a = -1$ and $b = -1$

The atbash cipher is equivalent to a monoalphabetic substitution with the alphabet ZYXWVUTSRQPONMLKJIHGFEDCBA

### When was Atbash invented?

Atbash would have been imagined between -1000 and -500 (before Christ).

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NB: for encrypted messages, test our automatic cipher identifier!