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:
In 2043 your nephew imports those words into whatever wallet software exists
He derives a fresh receive address each time he adds funds
No address reuse, full HD wallet, forward-compatible with hardware wallets
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.
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.