Atbash Cipher Tool: Decode and Encode Text Online

What is the Atbash Cipher?

The Atbash Cipher is a classic symmetric encryption method and a type of substitution cipher. It works by reversing the alphabet and replacing each letter with its counterpart from the opposite end of the alphabet. For instance, the letter "A" is replaced by "Z," "B" by "Y," and so on. Since the Atbash Cipher uses a fixed mapping, its encryption and decryption processes are the same: inputting the ciphertext will give the plaintext, and vice versa.

This cipher dates back to ancient Hebrew times and, despite its simplicity, remains an interesting and classic encryption technique in the history of cryptography.

How Does the Atbash Cipher Encrypt?

The encryption process for the Atbash Cipher is very straightforward and involves the following steps:

1. Choose the Alphabet: The Atbash Cipher typically uses the standard alphabet (e.g., "ABCDEFGHIJKLMNOPQRSTUVWXYZ") for encryption, but you can also use a custom alphabet to support different languages.
2. Character Substitution: Each letter in the plaintext is substituted with the letter from the opposite end of the alphabet. The first letter (e.g., "A") is swapped with the last letter (e.g., "Z"), the second letter (e.g., "B") with the second-to-last letter (e.g., "Y"), and so on.

Example

Using the alphabet "ABCDEFGHIJKLMNOPQRSTUVWXYZ" to encrypt "HELLO":

• H → S
• E → V
• L → O
• L → O
• O → L

Therefore, the plaintext "HELLO" becomes the ciphertext "SVOOL".

How Does the Atbash Cipher Decrypt?

The decryption process for the Atbash Cipher is exactly the same as the encryption process. Since the cipher is symmetric, the encryption step is simply reversed: replacing each letter with its opposite counterpart. Repeating the same substitution process during decryption will recover the original plaintext.

Example

To decrypt the ciphertext "SVOOL":

• S → H
• V → E
• O → L
• O → L
• L → O

Thus, the ciphertext "SVOOL" decrypts to the plaintext "HELLO".

How to Use the Atbash Cipher Tool?

1. Input Plaintext or Ciphertext: Enter the content into the appropriate input box, depending on whether you want to encrypt or decrypt.
2. Customize the Alphabet: The Atbash Cipher allows you to customize the alphabet. You can input a custom alphabet, such as uppercase letters, lowercase letters, numbers, or even characters from other languages.
3. Ignore Unknown Characters: During encryption or decryption, you can choose whether to ignore unknown characters (such as spaces, punctuation, etc.). If this option is enabled, the system will skip these characters and only encrypt or decrypt the letters.
4. View Results: The system will automatically encrypt or decrypt the text according to the settings. The result can be copied directly or saved to a local file using the download option for future use.