🔐 Security Teaching Toolkit

1. Look at the row of buttons at the top of the page: How to Use This, Encryption Playground, Firewall Rule Lab, Quick Reference. Those are the four sections of this toolkit.
2. Click a button to open that section. The button you're on turns teal (bright green-blue) so you always know where you are.
3. Everything reacts to clicking, typing, or picking from a dropdown. There's no save button and no way to mess it up, so try things and see what happens.

1. Open the Encryption Playground tab.
2. Find the box labeled Message and type any short sentence.
3. Find the box labeled Shared key and type any single word, like a password.
4. Look below at Ciphertext, it updates automatically into a string of letters and numbers. That's your message locked.
5. Find Try decrypting with this key and type the exact same word you used as the shared key. The Decrypted result box will show your original message again.
6. Now change that key to a different word instead. Watch the decrypted result turn into unreadable symbols. That's what happens when you don't have the right key.
7. Scroll down to the mailbox demo. Type a message, click Lock with Josh's PUBLIC key, then click Unlock with Josh's PRIVATE key to see it open. Click the red button instead to see it get rejected.
8. Scroll down further to the paint-mixing demo. Pick a public paint and two secret paints, Alice and Bob's towers paint themselves immediately, that's their own paint, no reason to hide it from themselves. Click Step 1 and watch two little blobs travel across the wire, Alice's mixture heading to Bob, Bob's heading to Alice, both crossing paths where Eve is tapping the line in the middle. When they land, Alice and Bob each reveal what they received from the other, and Eve reveals what she intercepted. Click Step 2 to watch Alice and Bob each stir their own secret into what they received, landing on the exact same final color, even though Eve never saw it. Change any color and the demo resets, so you can try it again.

1. Open the Firewall Rule Lab tab.
2. At the top is a table. Each row is one rule, read left to right: Source, Destination, Port, Protocol, Action.
3. Click the green ALLOW or red DENY word in any row to flip it.
4. Use the up and down arrows (▲▼) on the right of each row to move it higher or lower. Order matters, the first rule that matches a packet wins.
5. Click + Add rule to create a new row, then use the dropdowns to fill it in.
6. Click ▶ Send sample traffic (5 packets) to send 5 example connections through your rules automatically. Watch the log on the right mark each one ALLOW or BLOCK, in real time.
7. Want to test something specific? Use the Or test one custom packet boxes, pick your options, and click Test this packet.
8. Curious what a bad setup looks like? Click ⚠️ Load broken example, then send traffic again. Everything gets blocked, because the "block everything" rule is now sitting first in line.
9. Click ↺ Reset to working rule set any time to start over from the safe default.

This tab is a plain list of definitions, nothing to click. Use it if you or a classmate forgets what a term means during questions.

Type a message and a shared key. The same operation that locks it is the one that unlocks it, only if the key matches exactly.

Change the "try decrypting" key to anything else. Same ciphertext, wrong key, pure garbage. That's the whole point of a key.

Anyone can lock a message with Josh's public key, like dropping a letter in a mail slot. Only Josh's private key opens it.

Notice: the key that locks is not the key that unlocks. That's the entire difference from symmetric encryption above.

Grounding: Lecture 7 Slide 19 mentions public and private keys for TLS, IPsec, and SSH, that's the anchor. The symmetric/asymmetric terms, the analogies, and this whole playground are supplemental, not in the lecture itself.

Alice and Bob each hold two paints: their own secret, and a shared public paint everyone can see. Each mixes their two paints and sends the mixture to the other, over a line Eve is tapping. Alice and Bob both receive a mixture, Eve only ever watches one pass by.

Notice: both sides land on the exact same final color, but neither the public paint, Alice's sent mixture, nor Bob's sent mixture was ever the shared secret itself. Nobody watching the wire, not even Eve, can "unmix" a mixture back into its two ingredient paints, that one-way difficulty is standing in for how hard it is to reverse the modular exponentiation real Diffie-Hellman actually uses.

Further study: 📺 Diffie-Hellman Key Exchange, Computerphile (~8 min), the classic version of this same paint-mixing analogy (Alice / Eve / Bob and all). Good second analogy to have ready in class beyond the mailbox-slot one above.

Grounding: solid. Lecture 7 Slide 19 says encryption "may be used to secure data both in transit and when stored," almost word for word.

Click ALLOW/DENY to flip an action. Use ▲▼ to reorder. Order changes the outcome. 🗑 deletes a rule.

Grounding: Lecture 7 only mentions firewalls in passing, as a hardening control (Slides 12, 16, 25, 30, 37). The rule table, the fields, the ordering logic, and this whole simulator are supplemental, built specifically to satisfy this topic's hands-on DLO.