When my nephew was born I wanted to give him some special gift related to BTC. I wasn't sure if giving him an electronic hardware wallet is the best option as who knows what happens to the electronic in 18 years. So I decided to make a "paper wallet" but with something more durable using steel and etching it with a laser engraver. On the front is the public key with a QR so they can receive anytime (birthday, christmas ...) and on the back is hidden the private key under a scratch foil.
Now I have my own child and want to do something similar so Im searching for improvements ideas
This is the prototype:
Mantener la idea emocional PERO mejorar la arquitectura:
-> Regalo educativo + custodia real
-> entregar una dirección pública (watch-only / QR)
-> los fondos están en una multisig real (2/3) puedes usar incluso Blue Wallet
-> el niño no tiene acceso inmediato
-> pero puede “ver crecer” su Bitcoin
BIP85 + seed derivada
-> generás una seed dedicada para el niño
-> separada de tu patrimonio
-> podés regenerarla si perdés backups
-> no exponés la master
It's pretty cool for a gift! I'm curious how you get the private key under the foil?
I bought a bunch of those foils from aliexpress its called "SCRATCH OFF Stickers" its self adhesive and you just put it on.
Cool! So you don't have to rely on a third party for engraving the private key.
This seems like a fun way to give Bitcoin gifts in general.
Not concerned about address reuse then?
Based on my current knowledge address reuse is a concern if its going In / Out , In / Out ... but in this case its going only IN so shouldn't be an issue. Hopefully when the kids reach a certain age they scratch the back and move everything out and never again use the card itself.
Summary generated with AI because I'm lazy:
Risks (Receiving Only)
Total Balance Visibility: Every sender sees your entire wallet balance 24/7.
Income Tracking: Senders can see every other transaction you receive, mapping your sources and frequency.
Physical Targeting: Publicly visible high balances make you a target for theft and "wrench attacks."
Address Poisoning: Scammers send "dust" from look-alike addresses to trick you into accidentally copying their address for your next deposit.
who will be sending the child bitcoin and will have access to the public address? The family so I doubt :
family will map the transactions and cause a wrench attack :D
Also if bitcoin does not drop back to like 10 bucks then on this card there will be never to much bitcoin ( like full coins).
Add a QR code linking to @DarthCoin guides 🤣🤣🤣
🤣🤣🤣 that was a good joke, who knows if the domain still exists in like 10-15 years, Its more: the adults will have to educate like in every way of life with children.
Como experto en custodia, no recomiendo nunca esos sistemas es preferible cualquier otro formato, podes usar Nunchcuck que le podes dejar herencia en vida para determinada fecha, o bien podes tener bloqueado por tiempo mientras vos estas en vida.
Si te sucede algo el hereda el regalo, o cuando cumple la edad que quieras dejas de dar prueba de vida y hereda..
Estos sistema de tarjetas se han dejado de usar, no se recomiendan
It’s a brilliant idea for gifts that span generations.
To @DarrelXero's question — yes, address reuse is worth thinking through here.
The practical risk over 18 years:
Every deposit to this fixed address is visible on-chain forever. Anyone who knows the address (e.g. gift givers who sent to it) can watch the balance. Privacy degrades with every additional deposit.
More importantly: until the first spend, the public key behind the address is unknown to the world. Once your nephew ever spends from it, the public key is revealed. In a post-quantum future (18 years out is relevant), exposed public keys on unspent outputs become a real concern.
What would improve the design:
Instead of engraving a raw private key, consider engraving the BIP39 seed phrase (12 or 24 words) on the steel. Then:
The emotional appeal of the gift stays intact — seed words on steel are even more robust than a single private key, and the scratch-foil concept works perfectly for the words.
The single-key paper wallet is a nice object. The seed-phrase version is a nice object and better security architecture.
The steel engraving is a beautiful object and a great instinct — durability over 18 years matters. The design is almost right. One architecture improvement worth considering:
Engrave a BIP39 seed phrase instead of a raw private key.
Here's why it matters for your use case specifically:
A raw private key is locked to one address forever. Every birthday and Christmas deposit to that same address is publicly visible on-chain. Anyone who sends to it (including you) can watch the balance. Address reuse is fine for receiving, but it signals "this is a cold storage wallet" to anyone watching the public key space.
More importantly: the moment your nephew ever spends from it, the public key is exposed on-chain. In 18 years — which is genuinely in the post-quantum planning horizon — exposed public keys on large balances carry real risk.
A seed phrase solves both problems. Your nephew imports those words into whatever wallet software exists in 2043, derives a fresh receive address every time someone sends funds, and the full HD wallet is forward-compatible with anything. The steel stays the same. The security is better.
The scratch foil works perfectly for a 12-24 word grid instead of a hex key. If anything, a seed phrase makes the physical object feel more like a real Bitcoin artifact — words, not a string of hex.
One more thing: if you can add a simple note like "do not digitize, do not photograph" on the front, you've built the best security education into the gift itself.