RSASHAAESKEYMOD0101LOCKDH
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Explore, Encrypt, Decrypt, and Learn Cryptography.

Classical Cryptography

Vigenère Cipher

The Vigenère Cipher is a polyalphabetic substitution cipher that uses a repeating keyword to shift each plaintext character.

Try in Interactive LabBack to Algorithms

Algorithm Steps

  1. 1Take plaintext input.
  2. 2Take keyword input.
  3. 3Repeat keyword to match plaintext length.
  4. 4Convert letters to numeric values.
  5. 5Apply Vigenère encryption or decryption formula.
  6. 6Convert numeric results back to letters.

Formula

Encryption: Cᵢ = (Pᵢ + Kᵢ) mod 26
Decryption: Pᵢ = (Cᵢ - Kᵢ) mod 26

Example

Plaintext: ATTACKATDAWN
Keyword: LEMON
Encrypted text: LXFOPVEFRNHR
Decrypted text: ATTACKATDAWN