Free online Vigenere Cipher encryption and decryption tool. A polyalphabetic substitution cipher using a keyword, more secure than the Caesar Cipher. Supports custom keywords, preserving spaces and punctuation. Perfect for learning classical cryptography.
Enter Content:Type or paste the content you want to process.
Configure Options:Adjust settings as needed.
Get Results:Copy the result once done. All processing is local - no data is uploaded.
The Vigenere Cipher is a polyalphabetic substitution cipher using a keyword, invented by French cryptographer Blaise de Vigenere in the 16th century. It determines each letter's shift based on the keyword, overcoming the Caesar Cipher's single-shift weakness.
The Caesar Cipher uses a fixed shift for all letters — a monoalphabetic substitution. The Vigenere Cipher determines the shift amount based on each character of a keyword, so different positions use different shift tables — polyalphabetic substitution.
Your keyword should: 1) Be memorable but hard to guess; 2) Be moderate length (8-20 characters); 3) Contain letters (longer keywords are more secure). Avoid common words like password, key, or secret.
The Vigenere Cipher was considered unbreakable in medieval times, but modern cryptanalysis techniques (like Kasiski examination) can crack it relatively easily. It is not suitable for real security needs, but is invaluable for learning cryptographic history.
The Vigenere Cipher is based on Latin alphabet shifting and doesn't apply to Chinese. This tool preserves Chinese characters and non-letter characters unchanged.