ICT-Health Understanding encryption by using it

Secret writing that no one can crack

A padlock built out of interwoven ribbons, next to a stylised chip contact area from a card.

Every time you send a message, something happens that no supercomputer on Earth can undo. Not because it's secret — the formulas are just sitting on Wikipedia. But because the math behind it is so clever that knowing how it works doesn't get you a single step further.

This site lets you take that math into your own hands. No video, no picture of a padlock with a little key. Every chapter has buttons, and behind those buttons runs the exact same code your bank, WhatsApp and your ID card use. You make a key, you encrypt something, you change one letter and you watch it all fall apart.

You need nothing for this except this browser. No prior knowledge, no advanced math. Every word you might not know gets explained right when you need it.

What you're going to discover

  1. Base64: not encryption
    Why something that looks like secret writing usually isn't — and how you "crack" it in two seconds.
  2. Hash functions
    How you turn a book into a 64-character fingerprint, and why no one can get the book back out of it.
  3. Why password hashes break
    What really happens when a site gets "hacked", and why a good password survives anyway.
  4. Symmetric encryption
    Julius Caesar's secret writing, and what's been improved on it in 2000 years.
  5. Asymmetric encryption
    A lock anyone can click shut but only you can open — it sounds impossible and still works.
  6. Elliptic curves: the maths in your pocket
    A curved line where you can "add" points, and why that line sits inside the chip of your ID card. With a graph you can click on.
  7. Digital signatures
    How you prove that you wrote something, without a pen, in a way no one can fake.
  8. Hybrid encryption: how it really works
    How everything above comes together in the padlock at the top of your browser.
  9. Secret post: unbreakable messages
    Make your own key card, print it, swap it with your friends, and send each other messages over WhatsApp that no one else can read.
  10. The Belgian eID
    Put your ID card in a reader and watch everything from this site happen for real.

Three agreements

You're allowed to break everything Type nonsense, click in the wrong order, change one letter where you're not supposed to. That's exactly the moment you learn something.
Nothing leaves your device The demos run in your own browser. What you type never goes anywhere. Only the last chapter needs a server, and that's clearly flagged there.
You don't need to know the math But at the end of every chapter there's a little box with the mathematical idea behind it. If you read that and think "I want to understand this" — then you already know what to pick later on.

Why this is math, and not computer science

Computers carry this out, but they didn't come up with it. The ideas come from mathematicians who wondered: does there exist a calculation that's easy to do but impossible to undo? Prime numbers, clock arithmetic, curves in a plane — things that for centuries were only "beautiful", turn out to be exactly what the internet needed. Whoever masters this field builds the locks the whole world relies on.