Atbash Cipher
Yaser Rahmati | یاسر رحمتی
Last updated
Yaser Rahmati | یاسر رحمتی
Last updated
The Atbash Cipher is a type of substitution cipher, which is a method of encrypting text by replacing each letter in the plaintext with another letter. The Atbash Cipher is a simple and ancient encryption technique that dates back to biblical times. Here's a detailed, step-by-step explanation of how it works, along with examples.
The Atbash Cipher is a monoalphabetic substitution cipher where each letter in the alphabet is replaced with its reverse counterpart. The basic idea is that the first letter of the alphabet (A) is substituted with the last letter (Z), the second letter (B) with the second-last letter (Y), and so on.
To create the Atbash Cipher alphabet, you write out the alphabet in order and then write it in reverse order directly beneath it:
| Plaintext Alphabet | Cipher Alphabet |
|---|---|
To encrypt a message using the Atbash Cipher:
Replace each letter in the plaintext with its corresponding letter from the cipher alphabet.
Write down the plaintext: H E L L O
Find each letter in the plaintext alphabet and substitute it with the corresponding letter in the cipher alphabet:
H -> S
E -> V
L -> O
O -> L
So, "HELLO" becomes "SVOOL" when encrypted using the Atbash Cipher.
To decrypt a message encrypted with the Atbash Cipher:
Use the same Atbash Cipher alphabet since encryption and decryption are symmetric (the process is the same in both directions).
Write down the ciphertext: S V O O L
Replace each letter in the ciphertext with the corresponding letter from the plaintext alphabet:
S -> H
V -> E
O -> L
L -> O
So, "SVOOL" becomes "HELLO" when decrypted.
Simple and Easy to Implement: The Atbash Cipher is easy to use and understand, making it suitable for educational purposes.
Symmetric: The same algorithm is used for both encryption and decryption.
Weak Security: The Atbash Cipher is not secure by modern standards. Because there is only one way to encrypt and decrypt, it's easy to break with a frequency analysis or even brute force.
The Atbash Cipher has historical significance, particularly in ancient Jewish texts. It was used in the Book of Jeremiah in the Bible to hide certain names. For example, "Sheshach" was used as a coded form of "Babylon" using the Atbash Cipher.
While the Atbash Cipher is not used for serious encryption today due to its simplicity, it is still used as a teaching tool and can be found in puzzles, games, and certain forms of recreational cryptography.
Let's encrypt the sentence "SECRET MESSAGE."
Write down the plaintext: S E C R E T M E S S A G E
Replace each letter using the Atbash Cipher alphabet:
S -> H
E -> V
C -> X
R -> I
E -> V
T -> G
M -> N
E -> V
S -> H
S -> H
A -> Z
G -> T
E -> V
So, "SECRET MESSAGE" becomes "HVXIVG NVHHZTV" when encrypted.
If you were to decrypt "HVXIVG NVHHZTV" back into the original message:
Replace each letter using the Atbash Cipher alphabet:
H -> S
V -> E
X -> C
I -> R
V -> E
G -> T
N -> M
V -> E
H -> S
H -> S
Z -> A
T -> G
V -> E
This gives you "SECRET MESSAGE" back.
The Atbash Cipher is a simple substitution cipher that flips the alphabet.
It is easy to understand and use but offers no real security.
It has historical significance and is useful for educational purposes.
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