Quantum Computing and Address Reuse Dilemma

Been thinking about address reuse and quantum computing. If we never spend from an address, we're kinda safe, right? But juggling a ton of addresses gets tricky, especially with giveaways and repeat payments. Privacy risks are one thing, but security's got me worried.

There's a solution to this from way back, BIP32 with hierarchical deterministic wallets. Just back it up once and you can generate tons of addresses, no hassle.

Sure, but generating all those extra addresses feels impractical. Recovering a wallet with the seed isn't always straightforward. Different wallets have different paths and accounts. Honestly, I try to keep things simple.

The key is to keep your main stash separate. If you store it on a rarely used address, that's like securing 80-99% of your coins. Just keep smaller amounts on the other addresses. Gotta think this stuff through, it’s all about context.

Scary stuff, but not really due to node spending policies. We still don’t know how fast quantum computers can crack keys. If one finds a public key, they can’t double spend a transaction that's already out there.

Nah, they can use RBF to replace the transaction. Plus, every node has its own mempool, so they can differ a lot. If keys can be broken in real time, competing transactions could hit the network at the same time.

To keep it simple, consider using BIP85 child SEEDs for wallets with default addresses for inheritance. Use your main SEED for fresh addresses, moving funds when you spend. Hiding used addresses keeps clutter down.

True that. Even if RBF isn’t flagged, most nodes set to Full RBF can swap out unconfirmed transactions. If a bad actor has the private key, they can easily replace the transaction.

A quantum computer won’t bother with low-value addresses. They’d probably aim for high-value ones first. We’re not there yet, and it won’t be a quick process to crack a public key. The attacker has to be careful.

There’s a better way to secure funds if this ever happens. Tadge Dryja's idea involves a soft fork to use a quantum-proof method before submitting transactions from vulnerable addresses.

Yeah, breaking keys with quantum tech won't be as easy as it seems. Only high-value addresses would be targeted, and I doubt I’d be one of them.

Totally agree. I anticipated you’d mention that recovery method. It’s more complex than just submitting a transaction directly, but we should still prepare for anything, even if it’s not the best option.

Only when you spend from an address is the public key exposed. Just receiving funds keeps the address safe from quantum risks.

Exactly. No need to go over basics repeatedly. Some posts here are just wrong. Ignore them and move on.

I hope you’re mindful of privacy when moving coins. Consolidating UTXOs defeats owning multiple addresses. It’s wild how people think Bitcoin would be the first target once quantum computers are a thing.

Why is managing multiple addresses a problem? My wallet handles that just fine. I’ve used tons of addresses, most are empty now. Silent Payments could help avoid reuse, but it seems too complicated.

I’m not sure about that. Bitcoin Core’s gap is set at 1000 addresses, so you won’t hit that limit easily. Electrum lets you raise it easily too.

Even with quantum computers, SHA-256 is only weakened for brute-force from 2^256 to 2^128. So, we’re not completely doomed.