Explain like I'm five · Security

What is Privacy?

Privacy and personal data protection, told as a story about treating the visitor's name, home, and birthday in the castle roster as the visitor's own.

my name, my home, my birthdayCASTLE ROSTERname: Minsuhome: 3rd house past the riverbirthday: first day of springfavorite bread: ryekept for a whilea visitorthe clerkwhat's written belongs to the visitorthe castle only keeps it for a while — the visitor is the owner

The castle roster holds the visitor's name, home, and birthday.To deliver bread, the castle needs a name and a home. But those belong to the visitor. The castle only keeps them for a while.

writes down everythingnever even askedMinsu's homehands it to anyonethe visitor has no ideabirthday·homeit got stolenand nobody tells the visitorbecause the castle treats the visitor's things as its own

Trouble starts when the castle treats the visitor's things as its own.It writes everything without asking, hands it to anyone, and when a thief takes it, tells the visitor nothing. The visitor has no idea where their name tag went.

just your name, for the bread deliveryname: Minsubread: rye(that's all)ROSTER PROMISES1. write only what's needed2. say why, before writing3. erase it when asked4. if it's lost, tell them at oncevisitorclerkjust the two lines neededthe visitor's name tag belongs to the visitor — the castle only borrows itask before you write, guard what you wrote, give it back when asked

Privacy is the promise to treat the visitor's name tag as the visitor's own.The castle only borrows it. So ask before you write, write only what's needed, guard what you wrote, and give it back when asked.

Only what's neededbread needs a name and a home
Ask firstand say what it's for
Erase when askedthe spare chest copy too
Tell them if it's losthiding makes it worse
may I write it?ask firstand say whyMinsuNo. 17to others, a number insteadthe name stays in the castleerase it, pleaseMinsuerase when askedthe spare chest copy tooto Minsulost? tell them at oncenever hide itthe four promises hold the whole time the visitor is with the castle

This is what keeping the promises looks like.To others, a number goes out instead of the name. Erasing includes the copy in the spare chest. If it's lost, the playbook says: tell the visitor at once.

the inspectorwhy was it written, and does the visitor know?PROMISESasked first ✓here it isname tagred stamp, until burning daytreat the visitor's as the visitor's — and the inspector smiles, and so does the visitor

The inspector comes and asks: why was it written, and does the visitor know?The name tag gets a red stamp, a burning day, and a doorkeeper who keeps it inside the castle. Treat the visitor's as the visitor's, and the inspector smiles — and so does the visitor.

In one breath

Privacy = the visitor's name, home, and birthday in the castle roster are the visitor's own — so ask first, write only what's needed, hand out a number instead, erase when asked, and tell them at once if it's lost.

It starts from the principle that personal data (PII) belongs to the person. Consent and purpose limitation, data minimization, handling deletion requests, pseudonymization, and breach notification are the core, and regulators check against rules like GDPR and national privacy laws.

When grown-ups say it

Personal data (PII)
The visitor's name tag. Name, home, birthday, face — anything that says who someone is. The visitor owns it.
Consent
Asking before writing. May I write it? The visitor may say no.
Purpose limitation
Only for the reason you gave. A home written down for bread delivery can't be used for market ads.
Data minimization
Only what's needed. What you never wrote can never be lost. → every paper has a burning day
Deletion request
Erase it, please. When the visitor asks, erase it — spare chest copy included. → the spare chest kept far away
Breach notification
Telling them at once. If it's stolen, tell the visitor and the inspector within the set days. → the playbook for when a thief gets in
Pseudonymization
The number tag. To others, No. 17 instead of the name. The table linking number to name stays in the castle. → hiding the name
Data classification
A red stamp on the name tag. Once stamped, the doorkeeper and the key ring know to guard it. → a colored stamp on every paper
Next story
The Thief Who Steals the Wristband →
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