Extra 3 — The Crypto & Privacy Glossary

~4 min · plain-English decoder

This course uses a handful of words the crypto world treats as obvious. They're not. Here's the whole vocabulary with just enough context to make each one click. Skim it now, or jump back whenever a term trips you up.

Web3 — The umbrella term for an internet built on tools people own and control collectively, rather than platforms owned by a few corporations. Not a place you visit; a way of building things. The "3" frames it as the successor to web1 (read-only pages) and web2 (the social platforms that came to own your data).

Blockchain — A shared record book that thousands of independent computers each keep a copy of, so no single party can quietly rewrite history. Useful whenever a group needs to agree on the same facts — who owns what, what happened when — without trusting a middleman to keep the ledger honest.

Decentralization — Spreading control across many independent hands instead of concentrating it in one. The practical test: if any single company or server vanished tomorrow, would the system keep working? If yes, it's decentralized.

Open source (FOSS) — Software whose code is published for anyone to read, copy, and modify. The point isn't mainly that it's free — it's that you don't have to trust it, because you (or any expert) can verify exactly what it does. "FOSS" = Free and Open Source Software.

Peer-to-peer (P2P) — People, or their devices, connecting directly to each other with no company server in the middle. Like handing someone a note directly instead of mailing it through a post office that logs the sender, the recipient, and the date.

Encryption — Scrambling information so only someone with the right key can unscramble it. Two flavors matter: "in transit" (locked while traveling, but the company can still read it at either end) and the stronger kind just below.

End-to-end encryption (E2EE) — Encryption where only the sender and receiver hold the keys — not the app maker, not the servers in between. Even if the company is hacked or handed a subpoena, there's nothing readable to give up. The gold standard for private messaging.

Metadata — The data about your data: not the contents of your message, but who you talked to, when, for how long, and from where. It sounds harmless, but a map of everyone you contact and when often reveals more than the messages themselves — and many "encrypted" apps still leak it.

Zero-knowledge proof (ZK) — A way to prove a statement is true while revealing nothing beyond the fact that it's true. The classic example: proving you're over 18 without showing your birthday, name, or document number — just a verifiable "yes." It's how some systems let you prove things (you're a citizen, you have the funds) without handing over the underlying file.

FHE (Fully Homomorphic Encryption) — A technique that lets a computer run calculations on your data while it stays encrypted the whole time, then hands back an encrypted result only you can open — useful work done without the machine ever seeing what it worked on. Picture a sealed glovebox a worker reaches into but can't open. Still slow and early, but a genuine holy grail: it would end the trade-off between using cloud services and keeping your data private.

DePIN (Decentralized Physical Infrastructure Networks) — Real-world infrastructure — wireless coverage, maps, data storage — built and owned by thousands of ordinary contributors who get paid for what they provide, instead of one corporation owning it all. The gig economy flipped: you own a piece of the network, not just rent your labor to it.

Onion routing / mixnet — Techniques that bounce your traffic through several relay points so no one can trace where it started or where it's headed. This is the tech behind Tor; it hides not just what you send but that you sent anything at all. A mixnet adds extra scrambling of timing and size to close gaps plain onion routing can leak.

Self-custody ("your keys") — Holding your own digital keys and data yourself instead of letting a company hold them for you. Upside: nobody can freeze or seize what only you control. Catch: nobody can recover it for you either. Hence the old cypherpunk line, "not your keys, not your data."

Token — A digital unit of value, access, or voting power recorded on a blockchain. In DePIN it's how contributors get paid for providing real-world coverage; elsewhere it can represent ownership, membership, or a say in how a project is run.

That's the decoder ring. Everything in the course builds from these.