Using a web browser, visit the Cryptosystem Demo link. Get a partner and perform these steps. You will need to be able to send short emails to each other, or you can share a single computer on which each of you takes a turn using your own web browser. Each of you will turn in your own printout of your Cryptosystem Demo browser page after it is filled in.
1. Secret-Key Encryption. One of you will generate a Secret Key using Step 1 of the blue section of the Cryptosystem Demo. Make sure you keep your private key to yourself and make sure you can remember it.
2. Each of you should do this on your own: Compose a short message (just a few words). Enter this message as the Plaintext of Step 2 of the Cryptosystem Demo. Enter the Secret Key. Press the button to encrypt the message into Ciphertext, and copy/paste the Ciphertext into an email to your partner.
3. Each of you should do this on your own: Take the Ciphertext that you received from your partner and paste it into the Ciphertext field of Step 3. Enter the Secret Key. Press the button to decrypt the message into Plaintext.
4. Public-Key Encryption. Each of you should generate a Key Pair using Step 1 of the yellow section of the Cryptosystem Demo. Share your Public Key with your partner, but keep your Private Key to yourself.
5. Encrypt a message. Each of you should do this on your own: Compose a short message (just a few words). Enter this message as the Plaintext of Step 2b (We're skipping Step 2a for now). Enter your partner's Public Key. Press the button to encrypt the message into Ciphertext, and copy/paste the Ciphertext into an email to your partner.
6. Decrypt a message. Each of you should do this on your own: Take the Ciphertext that you received from your partner and paste it into the Ciphertext field of Step 3a. Enter your own Private Key. Press the button to decrypt the message into Plaintext. Is it readable?
7. Sign and Encrypt a message. Each of you should do this on your own: Compose a short message (just a few words). Enter this message as the Plaintext of Step 2a. Enter your own Private Key (to sign the message). Press the button to encrypt the message into Ciphertext. Copy/paste the Ciphertext into the top field of Step 2b. Enter your partner's Public Key. Press the button to encrypt the message, and copy/paste the Ciphertext into an email to your partner.
8. Decrypt and Verify a message. Each of you should do this on your own: Take the Ciphertext that you received from your partner and paste it into the Ciphertext field of Step 3a. Enter your own Private Key. Press the button to decrypt the message into Plaintext. Do not be surprised if it is unreadable. Copy/paste the message into the top field of Step 3b. Enter your partner's public key. Press the button to verify the signature.
