Vigenère Cipher Encrypt Decrypt Online

Encrypt and decrypt messages using the classic Vigenère cipher. This polyalphabetic substitution cipher uses a keyword to encrypt and decrypt messages with enhanced security.

Mode:

Key length: 0 characters (only letters will be used for encryption)

Characters: 0

Encrypted text will appear here...

Length: 0 characters

About Vigenère Cipher

What is Vigenère Cipher?

The Vigenère cipher is a polyalphabetic substitution cipher that uses a keyword to encrypt text. Each letter is shifted by a different amount based on the corresponding letter in the keyword.

How It Works

  • • Uses a repeating keyword for encryption
  • • Each letter shifted by keyword letter value
  • • Non-alphabetic characters remain unchanged
  • • Case preservation in output text
  • • More secure than simple Caesar cipher
  • • Polyalphabetic substitution method

Historical Significance

Invented by Blaise de Vigenère in 1586, this cipher was considered unbreakable for centuries and was called "le chiffre indéchiffrable" (the indecipherable cipher).

Modern Applications

  • • Educational cryptography demonstrations
  • • Historical cipher analysis and research
  • • Puzzle and game creation
  • • Understanding polyalphabetic ciphers
  • • Basic text obfuscation methods

Vigenère Cipher Rules & Examples

Encryption Process:

  1. Take each letter of the plaintext
  2. Find the corresponding keyword letter
  3. Shift the plaintext letter by keyword letter value
  4. Repeat keyword cyclically through the text

Key Features:

  • Keyword-based encryption system
  • Automatic key repetition
  • Case-sensitive processing
  • Non-alphabetic character preservation
  • Random key generation option

Security & Limitations

Strengths:

  • More secure than monoalphabetic ciphers
  • Frequency analysis is more difficult
  • Simple to implement and understand
  • Works with any alphabet size
  • Keyword provides additional security layer

Weaknesses:

  • Vulnerable to Kasiski examination
  • Short keywords create patterns
  • Index of coincidence analysis possible
  • Not suitable for modern security needs
  • Frequency analysis on longer texts

Tool Features

Core Functions:

  • Real-time encryption/decryption
  • Custom keyword support
  • Random key generation
  • Case preservation

File Operations:

  • File upload support (up to 10MB)
  • Download encrypted/decrypted results
  • Multiple file format support
  • Batch text processing

User Experience:

  • Dark mode support
  • Copy to clipboard functionality
  • Toast notifications
  • Responsive design