Encryption

• What encryption is and why it's needed, especially on wireless networks
• How wireless networks create and use a "master key" from the SSID + password
• How wired networks handle encryption differently (left to individual apps, e.g. HTTPS)
• The difference between plaintext and ciphertext
• Symmetric encryption — one shared secret key for both encrypting and decrypting
• Asymmetric encryption — a public key and a private key working as a pair
• Why large keys make encryption almost impossible to crack by guessing

Think about sending a postcard versus sending a sealed letter. A postcard can be read by literally anyone who handles it along the way — the postman, anyone who picks it up if it falls, anyone at all. A sealed letter, on the other hand, only makes sense to the person who's allowed to open it.

Data travelling across a network is like a postcard by default — anyone who intercepts it can read it. Encryption is the process of scrambling that data into a meaningless jumble before it's sent, so that even if it's intercepted, it's useless without the key to unscramble it.

You might wonder: if encryption matters on any network, why do your notes single out wireless networks as needing it "more"? Here's the reasoning: on a wired network, data travels down a physical cable — to intercept it, someone would need to physically tap into that cable, which is difficult and risky. On a wireless network, data is broadcast through the air as radio waves in all directions. Anyone with the right equipment sitting nearby — in a car outside your house, in the next office, even in the flat next door — can pick up those radio waves without ever touching a cable. That's what makes interception so much easier on wireless networks, and why strong encryption is critical there.

SSID password master key

every device that connects using the same SSID and password gets an identical copy of that master key

Symmetric encryption