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Bitcoin and quantum computing

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Re: Bitcoin and quantum computing

#51

Post by aeternum »

fluxusars wrote: post #35

The thing that supposedly sets Bitcoin apart from other cryptocurrencies is that it's deflationary and 'immutable', in that Satoshi is gone forever and any deviation of Bitcoin from his golden idea will result in undermining its essence. If Bitcoin can get quantum-attacked then, from a technical point of view, nothing will be lost. The Bitcoin core devs can issue a word-of-god statement stating that they'll roll back…

Bitcoin has had significant protocol upgrades before, including the highly divisive segwit. IMO immutability is a non-issue, there's plenty of evidence that Satoshi generally agreed that consensus via the longest chain (most PoW) wins.

Thus, upgrading the protocol/code to change the encryption to something quantum-resistant should be no more controversial a change than segwit. The community has already answered the "is it still Bitcoin". Yes it is, protocol and code is free to change given longest-chain consensus.

The problem will be what to do with legacy addresses. Never before have issued coins been forcibly deleted by a BIP. It could turn out that legacy addresses (including Satoshi's) that fail to have their coins moved after a deadline must be considered compromised and burned/destroyed. That has no precedent with bitcoin, although it does with ETH.

Anyone know if there's a way out that doesn't require this? Obviously there's no way to ensure all legacy address coins are moved by the deadline.

Re: Bitcoin and quantum computing

#52

Post by EthanHeilman »

tomtomtom777 wrote: post #46
EthanHeilman wrote: post #2

"A CRQC is an existential threat to Bitcoin (you might believe this is very low-likehood). Your measurement of this threat should literally be: (A) How likely you think it is a CRQC appears by a given time, multiplied by (B) How likely it is you think Bitcoin will not successfully upgrade by that time." It would interesting to survey people about their answers. My off the cuff answer is: 2030: A=0.05, B=0.01 2035: A=…

2045 A=~1.0 seems way off. CRQC is still a theoretical construct with hurdles to overcome. Yes, there is a significant risk that it will exist somewhere in the next decades, but there is also still a significant chance that it will be shown to be practically impossible.

That is not what I am hearing from people working on CRQC. A prediction of a CRQC with 10% by 2030 was made by own of the top experts in this field. 2045 used to be the pessimistic outlook by experts with a bunch of experts predicting earlier. Recent work has shown that CRQC is actual 20 times easier to built that previously thought, accelerating all timelines.

We are seeing significant progress in two different types of quantum computers, neutral atom and superconducting qubit.

No one really knows when it will happen, but the chance that it is practically impossible is held only by a small number of experts. Given what we have seen in 2026 has significantly shifted expectations.

Re: Bitcoin and quantum computing

#53

Post by cs702 »

fluxusars wrote: post #35

The thing that supposedly sets Bitcoin apart from other cryptocurrencies is that it's deflationary and 'immutable', in that Satoshi is gone forever and any deviation of Bitcoin from his golden idea will result in undermining its essence. If Bitcoin can get quantum-attacked then, from a technical point of view, nothing will be lost. The Bitcoin core devs can issue a word-of-god statement stating that they'll roll back…

The core developers need buy-in from nodes controlling > 50% of the computing power in the network to make any fundamental change to the network.

Re: Bitcoin and quantum computing

#55

Post by le-mark »

mmastrac wrote: post #12

The mostly likely quantum attack on Bitcoin will be a catastrophic transfer of large wallets to burn addresses along with a massive short position. No need to worry about washing stolen coins when you can just enjoy your "well timed" legal short position's windfall.

This would be the case if many people get the quantum “crack” at the same time. Since it would enable a pre-image attack, one actor could selectively mine blocks for a considerable time until others catch up. This could be going on now.

Re: Bitcoin and quantum computing

#56

Post by arijun »

I assume that the solution to this would be a modification of the cryptographic basis of Bitcoin. Is there any way at all to do that without leaving behind people who aren't available at the time of transfer? Like if Satoshi was in a coma and not dead, is there any way at all to harden Bitcoin against attacks that would leave his wallet accessible to him?

Re: Bitcoin and quantum computing

#57

Post by CyberDildonics »

mmastrac wrote: post #12

The mostly likely quantum attack on Bitcoin will be a catastrophic transfer of large wallets to burn addresses along with a massive short position. No need to worry about washing stolen coins when you can just enjoy your "well timed" legal short position's windfall.

Washing coins is not too difficult, you could split up values into lots of addresses and use them to buy other coins on other chains.

Re: Bitcoin and quantum computing

#58

Post by hatthew »

EthanHeilman wrote: post #52
tomtomtom777 wrote: post #46

Earlier quoted context omitted.

2045 A=~1.0 seems way off. CRQC is still a theoretical construct with hurdles to overcome. Yes, there is a significant risk that it will exist somewhere in the next decades, but there is also still a significant chance that it will be shown to be practically impossible.

That is not what I am hearing from people working on CRQC. A prediction of a CRQC with 10% by 2030 was made by own of the top experts in this field. 2045 used to be the pessimistic outlook by experts with a bunch of experts predicting earlier. Recent work has shown that CRQC is actual 20 times easier to built that previously thought, accelerating all timelines. We are seeing significant progress in two different type…

"Accelerated timeline" and "impossible" are not mutually exclusive. We may just reach the point where we conclude it's impossible sooner.

Not commenting on specific numbers/estimates.

Re: Bitcoin and quantum computing

#59

Post by glerk »

EthanHeilman wrote: post #49
glerk wrote: post #20

One thing that is not addressed: say this quantum attack happens tomorrow and everyone agrees it was an attack, what would prevent the community (miners, node operators, and users) to hard fork the chain at a snapshot before the attack, patch the protocol, and call that Bitcoin? There would be loss of value of course, but it is not unrecoverable. It’s worth remembering that Ethereum forked for much less (not even a b…

> fork the chain at a snapshot before the attack, patch the protocol, and call that Bitcoin? It won't work. The only way to authenticate who ones what coins is with signatures. If the signature algorithm is broken, you can't tell who the original owner is to move the coins to a safe signature algorithm. You need to more to safer signature algorithm before the break, after the break it is game over. > It’s worth remem…

> The only way to authenticate who owns what coins is with signatures

Maybe the only fully cryptographic absolutely zero-trust way? In practice there are very few bitcoin outputs that aren't linked to an offline identity and most users could easily produce a proof of ownership.

Of course, this is not ideal and everyone would prefer not to go down that route. But even if we prepare in time and Bitcoin provides a quantum-secure address scheme before "Q-day", what happens to all the wallets that didn't upgrade? Is it open season on them? Satoshi's wallet alone could crash Bitcoin's value as a currency if dumped on the open market. I think even with the upgrade plan in place, a hard-fork + recovery will be on the menu, with various degrees of community support.

Re: Bitcoin and quantum computing

#60

Post by [deleted] »

tomtomtom777 wrote: post #44
fluxusars wrote: post #35

The thing that supposedly sets Bitcoin apart from other cryptocurrencies is that it's deflationary and 'immutable', in that Satoshi is gone forever and any deviation of Bitcoin from his golden idea will result in undermining its essence. If Bitcoin can get quantum-attacked then, from a technical point of view, nothing will be lost. The Bitcoin core devs can issue a word-of-god statement stating that they'll roll back…

> The Bitcoin core devs can issue a word-of-god statement stating that they'll roll back the chain to before the attack, and all is well. Then they'll change the cryptography. That doesn't work, because once the signature scheme has been broken, nobody can prove that their coins are theirs. No roll back or word-of-god would help. The only way to make bitcoin quantum-safe, is to introduce a quantum safe signature sche…

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