A3 - Secret Keys and Symmetric Encryption

Video Resources

• Understanding Secret Keys
• Symmetric Encryption

Task 1

To help understand the idea of secret keys, take some time trying out cryptograms and one of these two websites:

• https://www.coolmathgames.com/0-cryptograms (this is my preferred site)
• https://api.razzlepuzzles.com/cryptogram

Once I've seen you working on these for a reasonable amount of time (maybe 10 minutes), I'll mark this task off as complete.

Task 2

The website https://anycript.com/crypto will allow you to encrypt and decrypt messages using a modern encryption algorithm. Begin by experimenting on this site.

To create an encrypted message:

• Type your original message in the Encryption Text box (top-left)
• In the Secret Key box, type in exactly 16 characters of your choice
• Leave all other options at their defaults
• Click the Encrypt button

To decrypt a message, use the bottom half of the form, pasting in the encrypted message as well as the key your used to encrypt the original message.

Once you are comfortable with this, find a partner (or let me know if you can't find one). You could also do this with a larger group in a circular manner. Email your partner an encrypted message as well as the encryption key. Then you should decrypt the message your partner sent you.

When you're done this, please show me both the emails you sent and received.

Reflection

There is one major pitfall to symmetric encryption, which we will discuss as small groups.