Atbash Cipher

This is a complete guide to the Atbash cipher and the tools you need to decode it. From the very earliest days of encryption, people have been using the Atbash cipher to hide the meaning of their text. It’s one of the simplest ciphers to decode – once you’ve worked out that its Atbash that you’re looking at.

You only need a pen and paper to take a crack at decrypting this mirror cipher, but if even that seems like too much work you can always use the tool below.

What is the Atbash cipher?

The Atbash Cipher is a really simple substitution cipher that is sometimes called mirror code. It is believed to be the first cipher ever used, and its use pre-dates Egyptian examples of encryption. To use Atbash, you simply reverse the alphabet, so A encodes to Z, B to Y and so on.

Atbash is considered a special case of Affine Cipher, a monoalphabetic substitution cipher. Affine is encrypted by converting letters to their numerical equivalent (A=1, Z=26 etc.), putting that number through a mathematical formula, and the converting the result into letters. With Atbash, the Affine formula is a = b = (m − 1), where m is the length of the alphabet.

Decoding or Encoding the Atbash Cipher

Text that has been encrypted with Atbash is most easily identified using frequency analysis. The most commonly used letters in English are E, T and A. When these have been encrypted using Atbash, they become V, G and Z. If you find a cipher text with a lot of Vs, there’s a good chance you are looking at Atbash.

This is a simple cipher to decode. All you need to do is create a translation table with the letters of the alphabet written from A to Z across the top and reversed along the bottom. Find the letter in your cipher text on the bottom row and look above it to see it decrypted.

History

While a lot of people look at ancient Egypt for the origins of codes (and that is where the first evidence of encryption was found) Atbash was actually the first cipher. It has its origins in Israel and was originally used to encrypt and decrypt the Hebrew alphabet. That’s where the name comes from, it’s a shortened version of Aleph Taw Bet Shin, The first, last, second, and second-from-last letters in the Hebrew alphabet.

Because of its simplicity, Atbash hasn’t been used for serious encryption purposes but it has been used to disguise words from casual readers. One example of this is in the bible where place names have been encrypted using Atbash in some chapters of Jeremiah. For example, Jeremiah 25:26 reads, ‘The King of Sheshach shall drink after them.’ Decrypting Seshach using Atbash gives you the more recognisable word, ‘Babylon’.

Usage

Like other simple substitution ciphers such as ROT13, Atbash doesn’t have any practical uses for encryption because it is so simple to decrypt. With no key needed to translate it, it is easily broken with just a pen and paper.

You will see Atbash pop up in puzzle games, and if you get practiced enough at it you can use it to hide the meaning of things from prying eyes, but it won’t stand up to any real scrutiny.

Like most substitution ciphers, you can play word games with Atbash – look for words with can be encrypted into other words, for example Hold & Slow, or Glow and Told.

Those who look for hidden meaning in words, such as Kabbalah-ists, use the Atbash cipher to dilute the power & meaning of words. Rather than using a word in its normal form, and at full power, they will encrypt it to change the numerical value of it which then reduces its impact.

Variants

Atbash in its regular form only encrypts the letters A-Z, leaving numbers and punctuation as plain text. Variant forms of the cipher do exist which include numbers and the most common punctuation symbols. This is similar to the way ROT13 has been expanded in the ROT18 and ROT47 ciphers.

Flip it and Reverse It

As the first cipher used, we can forgive Atbash for its simplicity. It was invented in days gone by, when far less people were literate and there were no computers who could flip the text with ease. It’s still worth knowing about because of its frequent appearances in puzzle games and the like, but if you really want to hide your secrets, you’re going to have to look elsewhere.

Sample Atbash Cipher

Code-breaking is not only fun, but also a very good exercise for your brain and cognitive skills. Why don’t you try breaking this example cipher:

gsrmp lu nv zmw gsv gviiryov gilfyov rn rm zg yvrmt ulfmw lfg wlvhmg zmblmv vohv pmld blfiv z sfnyft zhpvw wlilgsb ml lmv pmldh rg yfg blf ulfi zmw nbhvou ivkorvw la