Instructions: (1) choose and enter a six characters secret key, (2) type in a plaintext message in the assigned
box, (3) click on the 'Encrypt!' button. The corresponding ciphertext will show up in the ciphertext box,
(4) copy the ciphertext and send it to your communication partner (e.g. email).
Pass to your partner the secret key,
better to use a safe, (different), channel, and make sure to pass the web address for this demo.