Vigenère Cipher | Encrypt & Decrypt Text
Encrypt and decrypt text using the Vigenère Cipher. A classic polyalphabetic substitution method using a keyword.
How to Use This Tool
- 1
Select 'Encrypt' to secure a message or 'Decrypt' to reveal one.
- 2
Enter a 'Key' (e.g., LEMON). This key is required to decrypt the message later.
- 3
Type your message in the input box.
- 4
The tool processes the text instantly.
- 5
Copy the result. Note: Non-alphabetic characters are usually left unchanged.
Use Cases & Examples
Education & Learning
Perfect for students learning about the history of cryptography and polyalphabetic ciphers.
CTF Challenges
Solve 'Capture The Flag' cybersecurity puzzles that involve classic ciphers.
Fun & Games
Create secret messages for escape rooms, scavenger hunts, or puzzles for friends.
How Vigenère Cipher Works
Polyalphabetic Substitution: Unlike a Caesar cipher which shifts all letters by the same amount, Vigenère uses a keyword to shift each letter differently.
The Tabula Recta: The cipher uses a grid of 26 alphabets, each shifted by one place. The keyword letter determines which row to use.
Security: While stronger than simple substitution, it is vulnerable to frequency analysis (Kasiski examination) because the keyword repeats.
Frequently Asked Questions
Q.Is Vigenère Cipher secure?
A. No. It is a classical cipher and is easily broken by modern computers. Do not use it for sensitive data (passwords, banking, etc.).
Q.What happens to spaces and numbers?
A. This tool typically preserves spaces and punctuation, encrypting only the alphabetic characters (A-Z). This makes the message easier to read but slightly less secure.
Q.Why do I need a key?
A. The key determines the shift for each letter. Without the correct key, the output looks like random gibberish.
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