Scytale Cipher Encryption and Decryption Tool

Plaintext

Ciphertext

Key

Ignore Unknown Characters

Alphabet

Alphabet Details

What is the Autokey Cipher?

The Autokey Cipher is a cryptographic algorithm similar to the Vigenère Cipher, with the primary difference being the key generation method. The key for the Autokey Cipher starts with a predetermined keyword, and the rest of the key is automatically generated from the plaintext characters. In other words, the subsequent part of the key is identical to the plaintext, making each letter's encryption not solely dependent on a fixed key but instead varying progressively.

This method provides stronger encryption compared to the traditional Vigenère Cipher because it avoids the repetition of a fixed key, thus reducing the risk of brute-force attacks.

How Does the Autokey Cipher Encrypt?

The encryption process for the Autokey Cipher involves the following steps:

Choose an Alphabet: You can use the standard alphabet (e.g., "ABCDEFGHIJKLMNOPQRSTUVWXYZ") or a custom alphabet.
Set the Key: Choose a keyword to start the key. The subsequent characters of the key will be dynamically generated from the plaintext. For example, if the keyword is "KEY" and the plaintext is "HELLO", the full key becomes "KEYHELLO".
Encryption Process: Similar to the Vigenère Cipher, each letter in the plaintext is encrypted by combining its position in the alphabet with the corresponding letter in the key, resulting in the ciphertext.

For Example

Suppose the alphabet is "ABCDEFGHIJKLMNOPQRSTUVWXYZ", the plaintext is "HELLO", and the key is "KEY". By combining the column of the plaintext letter with the row of the key letter, we get:

H + K → R
E + E → I
L + Y → J
L + H → S
O + E → S

Thus, the final encrypted ciphertext is: RIJSS.

How to Use the Autokey Cipher Tool?

Choose the Alphabet and Key: Select or input the alphabet (supporting multiple languages) and set an initial key (which can be a word or string).
Input Plaintext or Ciphertext: Depending on whether you need to encrypt or decrypt, input the plaintext or ciphertext into the corresponding text box. The system will automatically handle the encryption or decryption and display the final result.
Set Unrecognized Character Handling: During the encryption or decryption process, you can choose whether to ignore unrecognized characters (such as spaces, punctuation, etc.). If enabled, the system will skip non-alphabetic characters, and only letters will be encrypted or decrypted.