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> not even the core part of Bitcoin blockchains, which are not vulnerable to quantum computers Um, what? Shor’s algorithm can take the public key of a wallet (

> not even the core part of Bitcoin blockchains, which are not vulnerable to quantum computers Um, what? Shor’s algorithm can take the public key of a wallet (present on any outgoing transaction in the ledger) and produce its private key. So now you can hijack any wallet that has transferred any Bitcoin. Notably only one successful run of the algorithm is needed per wallet, so you could just pick a big one if it takes weeks. It probably wouldn’t help you mine in practice, sure. Technically it would give you better asymptotic mining performance (via Grover’s algorithm) but almost certainly worse in practice for the foreseeable future.

tczMUFlmoNk 1y ago
> public key of a wallet (present on any outgoing transaction in the ledger) Genuine question: is this true? I only know a little bit about Bitcoin, but I thought there was a notion of an "extended public key" that's not exposed to the ledger, where each individual public key on the ledger is only used once, or something like that. I'm not at all confident in my understanding, so I'd love if you or someone else knowledgeable could help fill in the gaps.
- johncolanduoni 1y ago
  Extended public keys can be used to generate a family of addresses, but each transaction still needs the public key for any address that has sent money. Someone who uses it religiously can keep most of their money in addresses with no outgoing transactions, meaning their public key is actually secret and therefore cannot be attacked. But there’s so many addresses that have outgoing transactions and huge balances that it wouldn’t make a difference to an attacker - they could skim a fortune and cash out from wallets that are not so well protected.
  - tczMUFlmoNk 1y ago
    Thanks for explaining!
  - andy_ppp 1y ago
    The real issue is as soon as this is done once Bitcoin's value plummets to a fraction of what it was today while people scramble to fix the algorithms.

tczMUFlmoNk 1y ago

> public key of a wallet (present on any outgoing transaction in the ledger) Genuine question: is this true? I only know a little bit about Bitcoin, but I thought there was a notion of an "extended public key" that's not exposed to the ledger, where each individual public key on the ledger is only used once, or something like that. I'm not at all confident in my understanding, so I'd love if you or someone else knowledgeable could help fill in the gaps.

johncolanduoni 1y ago
Extended public keys can be used to generate a family of addresses, but each transaction still needs the public key for any address that has sent money. Someone who uses it religiously can keep most of their money in addresses with no outgoing transactions, meaning their public key is actually secret and therefore cannot be attacked. But there’s so many addresses that have outgoing transactions and huge balances that it wouldn’t make a difference to an attacker - they could skim a fortune and cash out from wallets that are not so well protected.
- tczMUFlmoNk 1y ago
  Thanks for explaining!
- andy_ppp 1y ago
  The real issue is as soon as this is done once Bitcoin's value plummets to a fraction of what it was today while people scramble to fix the algorithms.