Dive into classical cryptography with Explerify's Autokey Cipher Simulator. This interactive tool demonstrates how the Autokey cipher uses a combination of an initial key and automatically extended plaintext to encrypt messages.
Enter a message and define your initial key, then watch how the Autokey sequence is generated and used in:
E(x) = (Plain + Key) mod 26
Switch to decryption to learn how the ciphertext is reversed using:
D(x) = (Cipher − Key) mod 26
while recovering plaintext progressively to rebuild the extended key.
Ideal for high school and undergraduate students, this simulator builds intuition about polyalphabetic substitution, modular arithmetic, and classical cryptanalysis.
Explore more interactive experiments on our simulators page to deepen your understanding of physics, math, and computer science.