Vigenère Cipher
Encrypt and decrypt text using the Vigenère cipher with a keyword.
The Vigenère Cipher is a fast, accurate Security utility designed to encrypt and decrypt text using the vigenère cipher with a keyword. entirely in your browser with zero server data storage.
The key is repeated to match the text length. Only letters are used.
The Vigenère cipher uses a keyword to shift letters by different amounts, making it much stronger than Caesar cipher.
Example: Text "HELLO" with key "KEY" → H+K, E+E, L+Y, L+K, O+E
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Systems & Security Engineers • Applied Cryptography & High-Performance Web Tools
How to Use Vigenère Cipher
Switch Mode
Choose Encrypt or Decrypt.
Enter Text
Type or paste the message you want to encrypt or decrypt.
Provide Keyword
Enter a secret keyword (letters only).
Generate Key
Click Generate Key for a random 16-character keyword.
Process
Click to encrypt/decrypt or 'Show Work' to see step-by-step.
Practical Examples & Conversions
Message: HELLO, Key: KEY
RIJVS
Related Tools & Converters
Authoritative Standards & Citations
Calculations and algorithms on this page are implemented and verified in strict accordance with the following official technical specifications:
RFC 6238: TOTP: Time-Based One-Time Password Algorithm
Extension of the HMAC-based One-Time Password algorithm HOTP to support time-based moving factors.
NIST Special Publication 800-38D: Galois/Counter Mode (GCM)
Recommendation for block cipher modes of operation: Galois/Counter Mode (GCM) and GMAC.