Atbash

The Atbash cipher is a substitution cipher that operates by replacing each letter of the alphabet with its respective "opposite" letter. It is one of the simplest and oldest known ciphers.

In the Atbash cipher:

• The first letter of the alphabet ('A') is replaced with the last letter ('Z').
• The second letter ('B') is replaced with the second-to-last letter ('Y').
• This pattern continues for each letter, with each letter being replaced by its counterpart in the reverse order of the alphabet.

The Atbash cipher follows a symmetric pattern, where the encryption and decryption process are the same. Applying the Atbash cipher twice on a piece of text will restore the original message.

For example, let's encrypt the word "HELLO" using the Atbash cipher:

H -> S
E -> V
L -> O
L -> O
O -> L

So, "HELLO" would be encrypted as "SVOOL" using the Atbash cipher.

To decrypt an Atbash-encrypted message, you simply apply the cipher again, reversing the substitution process.

The Atbash cipher can be applied to the entire alphabet, including both uppercase and lowercase letters. Non-alphabetic characters such as numbers or punctuation marks are typically left unchanged.

It's important to note that the Atbash cipher is a relatively weak encryption method and provides minimal security. It was primarily used in ancient times when cryptographic techniques were in their early stages or for simple encoding purposes.