Cryptography Basics: Atbash Cipher 密码学基础之“埃特巴什码”

Atbash is a monoalphabetic substitution cipher originally used to encrypt the Hebrew alphabet.

In cryptography, a substitution cipher is a method of encrypting
by which units of plaintext are replaced with ciphertext, according to a
fixed system; the “units” may be single letters, pairs of letters,
triplets of letters, mixtures of the above, and so forth. (– Wikipedia)

To put it in simple terms, the Atbash Cipher is a very low-level cryptography method and can be decrypted easily by a simple guessing because the substitution pattern is rigid and obvious.

In other words, the algorithm is too simple.



For example, because in Atbash Cipher, A=Z, B=Y, and so forth, then

  • “AB” becomes “ZY”
  • “AM” is encrypted as “ZN”

If you encrypts the command “Attack at 6AM”, it becomes “Zggzxp zg 6ZN” in Atbash Cipher.

If your enemy has figured out you are using Atbash, your encrypted message would sound like a thunder to their ears.

One of my friends often plays the Atbash Cipher game with me.

For instance, when he wants to mention “VPN” which he fears would catch the attention of the censors, he would type “EKM”, and I know what he means.

Here you can play with it on this website:

or here: