A simple linear cipher originally used on the Hebrew alphabet.

How it works

Encoding

The Atbash cipher is pretty simple, and all its does is reverse the letters in the alphabet: A becomes Z, B becomes Y, ..., Y becomes B, Z becomes A.

Here's the full table:

Encoding the word crypto, we get:

C R Y P T O
X I B K G L

Decoding

We can observe that applying the code twice to a message letter, will leave us with the original message. To decrypt, we just have to re-apply the code.

X I B K G L
C R Y P T O

Cons

• Pretty simple and famous cipher.
• Frequency analysis can be used to crack the code, if the message is long enough.

Implementations

Source: CrypTools Cipher Repository