Vigenere Cipher
Encrypt and decrypt messages using the Vigenere polyalphabetic substitution cipher — enter your message and keyword and get the result instantly.
What Does This Tool Do?
Encrypt and decrypt text using the Vigenere cipher — a polyalphabetic substitution cipher that uses a keyword to shift each letter by a different amount, making it much harder to crack than a simple Caesar cipher.
Key Features
Polyalphabetic
Keyword drives a different shift per letter.
Both Directions
Encrypt and decrypt with the same key.
Preserves Case
Uppercase stays uppercase, lowercase stays lowercase.
Copy Result
One-click copy of the output.
How to Use
- Type or paste your message.
- Enter a keyword (letters only — spaces and numbers ignored).
- Click Encrypt or Decrypt.
Frequently Asked Questions
How does the Vigenere cipher work?▾
Each letter is shifted by the corresponding letter of the keyword (A=0, B=1, … Z=25). The keyword repeats to match message length. E.g. with key SECRET: S=18, so A→S, B→T, etc.
Is the Vigenere cipher secure?▾
No — it was considered unbreakable for centuries but can be cracked with the Kasiski test or index of coincidence analysis. It is used for educational purposes only.
Does it work with numbers and punctuation?▾
Non-alphabetic characters are passed through unchanged. Only A–Z letters are encrypted.
Complete Guide to Vigenere Cipher
When To Use This Tool
Use Vigenere Cipher whenever you need fast, accurate output without installing software. This tool is designed for speed, clarity, and repeatable results for day-to-day work.
Best Practices for Accurate Results
- Double-check the format of your input before running the tool.
- Test with a small sample first, then process larger data.
- Use Related Tools to verify, convert, or transform the output.
Why Users Prefer AdeDX
AdeDX tools are browser-based, free to use, and built to work across desktop and mobile devices. Most processing happens directly in your browser for fast performance and improved privacy.