PZ · The Guardians (safety systems for children) · lesson 5 of 8
level
Tinkerer (change · fix · combine) · two levels: ages 7–10 (grades 1–4) and an extra task for ages 11–13 (grades 5–7)
duration
10–15 min on screen + 10–15 min without a screen (with other children or an adult)
school link
supports Technology and Entrepreneurship (simple systems, logic) and the library's digital-safety lessons on passwords (DB-IB-01) as a cross-curricular topic
publisher
East Accelerator Foundation (Фондация „Източен Акселератор“) · host: kagami.bg
access
free · no account · no data collected · works offline
Sort ways of opening a door into three kinds: something you HAVE (key, card, fob), something you KNOW (code, secret word), something you ARE (fingerprint, face)
Deduce a three-digit game code from clues (logic, no guessing under time pressure)
Say that real home alarm codes and door codes are never told to anyone and never typed on a screen; game codes are invented
(ages 11–13) Explain “two things together” (card + code) and why a shared code is weaker than personal cards: the log cannot tell who came in, and a lost personal card can be switched off while the others keep working
KEY CONCEPTS
three kinds of authentication factor: know · have · are (NIST glossary)
two different factors together are stronger than one (NIST SP 800-63B-4, by analogy from logins to doors)
a lost or stolen pass should be switched off at once (NIST SP 800-63B-4, by analogy); the shared-code weakness is shown as reasoning, not as a statistic
fingerprint and face are sensitive personal data; adults decide; there must always be another way in without them (EDPB Guidelines 3/2019, section 5); the lesson collects nothing
STRUCTURE
goal → 1 Remember (3 warm-up questions: the magnet on the door, the password lesson DB-IB-01, what a key is for) → 2 Story (invented: Nia, Bobby and friends make a tent club with a secret code and a who-comes-in log with drawn animal symbols; 60–90 s) → 3 Worked example (table: have / know / are with examples and a strong and weak side) → 4 Try it (Predict: where does a code live? → Run: sort 7 cards into have / know / are → Change: club-door code puzzle, 3 rounds + 1 round for ages 11–13, digit wheels, per-digit kind feedback, no timer) + extra box for ages 11–13 (two things together; shared code vs personal cards — interactive comparison of two door logs) → 5 Unplugged (the group invents a secret club code — knock, gesture or numbers; a who-comes-in log with drawn symbols) → 6 Make your own (design a club pass card; ages 11–13: a two-thing door) → 7 What I learned (3-question check + skill badge, no points) → 8 I have a question (form: the child writes ≤280 chars, the parent enters an e-mail and consents; double opt-in; plus "Was it useful?" / "We did the lesson" buttons — aggregate counts only)
ANSWERS
predict: a code lives in your head (something you know)
sort: key, card, fob → have; number code, secret word → know; fingerprint, face → are
puzzle: round 1 → 350 (first 3, second 2 more than the first, third 0); round 2 → 123 (each digit 1 more than the one before, sum 6); round 3 → 444 (all equal, sum 12); round 4 (ages 11–13) → 603 (first is twice the last, middle 0, sum 9)
older: shared code log shows only “code · code · code” — nobody knows who came in, and changing it means everyone learns a new code; personal cards show 🦊 🐢 🦉, and a lost card is switched off alone
check: q1 b (something I know) · q2 c (the door card) · q3 a (I say it is the adults' secret and do not tell)
SAFETY
all game codes are invented and labelled as game codes; the child never tells or types real home alarm or door codes
biometrics mentioned only lightly: adults decide, nothing is collected; no photos or fingerprints are taken in the activities
no burglars or thieves; positive frame: the child is an engineer of the club door
nothing to buy; no personal data entered or stored; the page works offline
NEXT
DB-PZ-06 · Mine and Ours · back: DB-PZ-04 · Smoke and Heat
SOURCES · LICENCE
link only, facts retold in our own words: NIST CSRC Glossary, authentication factor (citing SP 800-63-4) — three types: something you know, have, are; checked 2026-11-01
link only, facts retold in our own words: NIST SP 800-63B-4 — two distinct authentication factors (AAL2); invalidate a lost/stolen authenticator immediately upon notification (sec. 3.2.1); online authentication, applied here by analogy to doors; checked 2026-11-01
link only, facts retold in our own words: EDPB Guidelines 3/2019 on video devices v2.0, section 5 (biometric data, art. 9 GDPR) — a controller using facial recognition for building access must always offer an alternative without biometric processing, such as badges or keys; checked 2026-11-01
licence: CC BY-SA 4.0 · https://creativecommons.org/licenses/by-sa/4.0/
METADATA
path
6 · social impact
determinant
physical environment
sdg_target
4.7
who_criterion
accessibility
impact_type
prevention · education
DIGCOMP 3.0
framework
DigComp 3.0 (JRC144121, doi:10.2760/0001149)
primary
none (technology-understanding lesson: how safety systems work; no primary DigComp 3.0 competence)
secondary
4.2 Protecting personal data and privacy
mapping
proposed 2026-11-01 by the lesson goal · confidence: medium · not a measured outcome
VERIFIED · 01.11.2026AI help: yesreviewer: awaiting teacher and psychologist
Key, Code, Card
Every door asks one thing: “May you come in?” The answer is a pass. It is something you have, something you know or something you are. Today you are the engineer of the club door.
⏱ 10–15 minTinkererThe Guardians · 5grades 1–7 · two levels
You will be able to sort passes into three kinds and crack an invented code from clues.
For the parent: a one-page guide — a secret-code game, a who-comes-in log and a talk about codes at home.
progress0%
01Remember
Think about each question, then open the answer.
How does the magnet on the door know the door is open?
Its two parts are no longer next to each other. You know it from the lesson “The Building's Senses”.
What makes a good password?
Long and hard to guess — like in the lesson “Passwords Even a Dragon Can't Guess”. And it is kept secret.
What is a key for?
It unlocks one door. Whoever has the key can come in.
02Story
This story is made up.
In the yard, Nia, Bobby and their friends are building a club — a tent made of blankets.
“We need a door!” says Bobby. “And a pass.”
“We don't have a key,” Nia laughs. “Let's invent a secret code!”
They decide: three knocks, a pause, one more. Only club members know it.
“And how will we remember who came in?” asks little Maya.
Bobby takes a notebook. Everyone chooses a sign: Nia is 🦊, Maya is 🐢, Bobby is 🦉.
When someone comes in, they draw their sign in the notebook. No names — only signs.
“Now our club is like a real building,” says Nia. “It has a door, a code and a log!”
03Worked example
There are three kinds of pass. Each one has a strong side and a weak side:
Kind
Examples
Strong side
Weak side
🎒 Something I have
key, card, key-fob chip
nothing to remember; a personal card can be switched off if it is lost
it can be left at home
🧠 Something I know
number code, secret word
nothing to lose
easy to tell someone else
🖐️ Something I am
fingerprint, face
always with me
very personal — adults decide about it
Some doors ask for two things together: a card and a code. That is safer.
An important rule: real home codes are never told to anyone and never typed on a screen. In the game the codes are invented.
04Try it now
1 · Predict
The club door opens with a code. Where is the code? Choose before you check.
2 · Run: have, know or am?
Tap a pass, then the box where it belongs.
3 · Change: the club door code
Read the clues and turn the three wheels. No hurry — think calmly. The codes are invented, just for the game.
For older children · ages 11–13Some doors ask for two things together — something you have and something you know. If someone finds the card, it is not enough without the code. Now compare two clubs. One has a shared code for everyone. The other gives everyone a personal card. Look at the door log:
05No screen: the club's secret code
You need: friends or family, a notebook and pencils. The club can be your room, a blanket tent or a corner of the classroom.
Choose the club door — a real door or an imaginary line on the floor.
Invent a secret code together: knocks, a hand gesture or three digits. It is just for the game.
Make a who-comes-in log. Everyone chooses a sign — an animal, a star, a flower. Whoever comes in draws their sign. No names needed.
One person is the door guard. They ask for the code and look at the log. Then you swap roles.
For older children · ages 11–13Add a second thing: besides the code, everyone has a cardboard pass with their sign. The door lets you in only with both together. Then imagine one pass is lost. What do you change — the whole code for everyone, or only that pass?
✋
Home codes are the adults' secret
Real alarm and door codes are never told to anyone and never typed on a screen. In the game we use only invented codes.
06Make your own
Make a pass for your club out of cardboard.
Draw your sign — an animal, a star or something else.
Write the name of the club.
Mark which kind of pass it is: have, know or am?
Show it at home and explain the three kinds of pass.
For older children · ages 11–13Draw a door with “two things together”: what must you have and what must you know? Think about someone who forgot their card. How will they get in without making the door weaker?
07What I learned
A pass is something I have (key, card), something I know (code) or something I am (finger, face).
Two things together — a card and a code — are safer than one.
Real codes are never told and never typed on a screen. In the game the codes are invented.
What do you know by heart without carrying it in your pocket?
Check yourself
1. A number code is something that…
2. Which one is “something I have”?
3. A friend asks for your home alarm code. What do you do?
🔐
Skill badge: “Door engineer” It is yours when you can show one pass of each of the three kinds and say which one is tidiest for the club. No points and no ranking — only a skill.
08I have a question
Do you still have a question? Write it here. It goes to your parent, not to strangers. Your parent confirms their e-mail first.
The form is loading… If it does not appear, write your question on paper and show it to a parent or teacher.
·Sources
Title: Key, Code, Card (DB-PZ-05) · Author: Children's Library, East Accelerator Foundation · Source: original content and original game code, 2026 · Rights: CC BY-SA 4.0.
US National Institute of Standards and Technology (NIST) — glossary: “authentication factor”: the three types are something you know, something you have and something you are. Checked 01.11.2026.
NIST — SP 800-63B-4: stronger checking needs two different factors together; a lost or stolen authenticator must be able to be invalidated immediately. The document is about logging in to systems, but the idea is the same for doors. Checked 01.11.2026.
European Data Protection Board — Guidelines 3/2019 (PDF), section 5: biometric data (finger, face) are especially personal; when used to enter a building there must always be another way without them, such as badges or keys. Checked 01.11.2026.
Licence:CC BY-SA 4.0 · Children's Library, East Accelerator Foundation, 2026. You may share and adapt this lesson if you credit the author and keep the same licence. Learning is free forever.
