Vigenère Cipher
A polyalphabetic substitution cipher, more secure than the Caesar cipher.
Usage
What is the Vigenère Cipher
The Vigenère Cipher is a polyalphabetic substitution cipher that uses a series of Caesar ciphers based on a keyword (key). It is harder to crack than the Caesar cipher because it obscures letter frequency patterns through varying shift amounts.
Steps
1. Set the key (a word or phrase containing only letters); 2. Enter text in the input box; 3. Click "Encrypt"; the key repeats to match the plaintext length and shifts each letter; 4. Click "Decrypt" to restore the ciphertext.
Notes
The key can only contain English letters; only English letters are processed, non-letter characters remain unchanged; more secure than the Caesar cipher but still weak, not recommended for actual encryption scenarios.