Decrypting History: Exploring the Origins and Significance of the Atbash Cipher

Photo by Natalia Y. on Unsplash

Cryptography offers us a way to interpret the deeper meanings hidden in plain sight. One of the earliest methods was used by the Kabbalists (a school of thought in Jewish mysticism), who used three methods to interpret Jewish literature. Those three methods were:

Notarikon

This method of deriving a different meaning from a word uses the letters of the word to stand for separate words. The word ‘notarikon’ is borrowed from the Greek language and was derived from the Latin word ‘notarius’ which stands for ‘shorthand writer’.

A common usage of notarikon in Kabbalah is to form sacred names of God derived from religious and biblical verses. One example of a notarikon is ‘AGLA’ which is interpreted as ‘Atah Gibor Le-olam AdonaiAtah Gibor Le-olam Adonai’ which means ‘You, O Lord, are mighty forever’.

Gematria

This method is probably one of the most famous, as it uses numerical values mapped onto the alphabets and uses those numbers to denote different values. A single word can yield several values depending on the cipher that is used. This method has been used to derive many modern systems and deserves a deeper understanding.

Temurah

This method used by the Kabbalists works by rearranging the alphabets of a word to derive a different meaning from it. And today we will be diving deep into one of the most popular cipher which many define as one of the building blocks of modern cryptography: the Atbash cipher.

Atbash Cipher

Cipher table

The Atbash Cipher is a monoalphabetic cipher substitution cipher that was used to encrypt Hebrew letters. It works by mapping the reverse order of alphabets onto the forward order of alphabets, then substituting the letters of the word for the corresponding letter on the reverse mapping. As a result, the last alphabet becomes the first, and the second alphabet becomes the second to last.

Plaintext: JEREMIAH
Ciphertext: QUIUNRZS

The name of the cipher is derived from first, last, second and second to last letter of the Hebrew alphabets > Aleph-Taw-Bet-Shin

In the book of Jeremiah, the word ‘Babylon’ is replaced with ‘Sheshach’ using the Atbash Cipher.

Jeremiah 25:26

“The king of Sheshach shall drink after them”

“The king of Babylon shall drink after them”

In terms of security, it provides no security as it lacks any sort of key and can only be encrypted in a single manner.

Implementing the Atbash cipher

fw='ABCDEFGHIJKLMNOPQRSTUVWXYZ'
bw='ZYXWVUTSRQPONMLKJIHGFEDCBA'
for(char c: text){
  if(c.isUpperCase())
    encoded += bw.charAt(fw.indexOf(c.toLowerCase())).toUpperCase()
  else
    encoded += bw.charAt(fw.indexOf(c))

Try out Atbash Cipher!