The Quantum Threat to Bitcoin: Implications for Miners, Nodes, and Wallets

[Davidvictorson]

Suppose that that there is a successful quantum attack on SHA-256. That it happened so quickly that Bitcoin has to move infrastructure with the nodes is transitioned to a quantum resistant software. What do you think would happen to the miners, the computation of the nonce, including all the mining hardware?  And by extension how would this affect Bitcoin wallets. Do you think we would need to get new wallets and migrate our funds from our old addresses?

[1714252713]

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[_act_]

This will not affect mining or nodes or bitcoin wallets. Only what that will happen is for bitcoin developers to develop quantum computer resistant one which may require an update nodes, miners and wallets.

Before bitcoin will not be able to be resistant against quantum computing, bitcoin developers would have created quantum resistant one.

[Lucius]

Suppose that that there is a successful quantum attack on SHA-256. That it happened so quickly that Bitcoin has to move infrastructure with the nodes is transitioned to a quantum resistant software. What do you think would happen to the miners, the computation of the nonce, including all the mining hardware?  And by extension how would this affect Bitcoin wallets. Do you think we would need to get new wallets and migrate our funds from our old addresses?

What you imagine does not make much sense, because today's quantum computers are far from being able to be a threat to Bitcoin in any way - and therefore the scenario you are talking about cannot just happen overnight. In other words, there is enough time for Bitcoin to adapt to this threat, and there are dozens of discussions on the forum where you can find a lot of useful information about the quantum threat.

For those who want to know more, interesting reading -> https://www.schneier.com/blog/archives/2015/08/nsa_plans_for_a.html

[d5000]

Suppose that that there is a successful quantum attack on SHA-256 ECDSA. That it happened so quickly that Bitcoin has to move infrastructure with the nodes is transitioned to a quantum resistant software. What do you think would happen to the miners, the computation of the nonce, including all the mining hardware?  And by extension how would this affect Bitcoin wallets. Do you think we would need to get new wallets and migrate our funds from our old addresses?

FTFY. SHA-256 isn't especially vulnerable to quantum computers afaik (it's more vulnerable to extremely fast traditional Von Neumann computers). It's the public key algorithm (ECDSA) which could generate some headaches in some decades.

But the attack will be slow and gradual. Let's say that a malicious entity has access _now_ to a quantum computer capable of running Shor's algorithm to break ECDSA, with a couple of thousands qubits.

-  First, they'll try to attack old P2PK transactions, as they provide the public key. Satoshi's coins are the prime example for that. We will thus see slowly Satoshi's money moving (be it because Satoshi himself moves them with P2[W]PKH/P2TR txes, or because the quantum hacker moves them). An attacker will need years for that step alone, so they'll be focusing on coins where it's unlikely that thay'll be moved.
- Second, they'll attack transactions with reused keys. These are more likely to be moved. First old ones, then newer ones. I think at least in this phase people will become increasingly aware of the danger, and devs will have probably created a new quantum-secure public key infrastructure for the addresses.
- And only in a third step they'll be able to attack non-P2PK keys while people are transacting. They have less than 10 minutes, as they need the public key, i.e. they have to wait until you spend the funds and then attack instantly.

(by the way: shouldn't we make one of the old threads on that topic sticky so the question doesn't pop up every couple of weeks?)

[HeRetiK]

Suppose that that there is a successful quantum attack on SHA-256. That it happened so quickly that Bitcoin has to move infrastructure with the nodes is transitioned to a quantum resistant software. What do you think would happen to the miners, the computation of the nonce, including all the mining hardware?  And by extension how would this affect Bitcoin wallets. Do you think we would need to get new wallets and migrate our funds from our old addresses?

Bitcoin's PoW scheme is the least likely component to be affected by quantum computing. Assuming quantum computers ever become more efficient at computing SHA-256 hashes than ASICs the worst thing that could happen is that quantum computers would get used for mining.

What could become problematic at one point is quantum computing enabling the derivation of the private key of an address from its public key. That scenario affects old addresses that have their public key exposed due to outgoing legacy P2PK transactions; assuming they still contain a balance due to address reuse. While that may involve potentially a tidy sum, the impact of such an attack would still be rather limited except for bringing old coins back into circulation (i.e. it seems to be likely that any coins potentially exposed in such a manner have been lost by their owner a long time ago). Correcting myself because I misremembered: That scenario affects old P2PK address that provide the public key directly and modern addresses after the public key has been exposed by an outgoing transaction. While critical, this would follow a slow timeline as described by d5000, especially since the step between cracking P2PK addresses and modern addresses -- on-the-fly, outside of address reusage -- is huge.

[philipma1957]

yeah all of the above about slow deliberate attacks against the early blocks makes sense if the attacker was a business trying to make money.

If the attacker is a government looking to wipe out BTC and 256bit  crypto safety.  They would do a few of satoshi's just to see how fast it takes them to do a single address.

Only need do a few.

Then do nothing except crack all of satoshi's addresses. Once they do that simply pull out every coin on them in under an hour.  This would crash BTC out and terrify all companies using 256 bit encryption.

If I live long enough to see this happen I would be very surprised as I think this is 50 years away at best.

256 bit encryption would be wise to to stay ahead of this by becoming 512 bit.

I also think it would happen until we develop cold fusion which would enable  easy power for a very big pc.

[BlackHatCoiner]

What do you think would happen to the miners, the computation of the nonce, including all the mining hardware?

The mining infrastructure won't be vulnerable. It's the security of the secp256k1 elliptic curve Bitcoin uses, that will need to change. And there will probably be a quantum safe hard fork which will come with a quantum safe algorithm.

And by extension how would this affect Bitcoin wallets. Do you think we would need to get new wallets and migrate our funds from our old addresses?

The developers will warn you to send your coins to quantum safe addresses. By the time that it will be trivial to work out a private key by a quantum computer within a reasonable time frame, any coins sitting on quantum unsafe addresses will be waiting to be claimed by the attacker.

[vjudeu]

What do you think would happen to the miners, the computation of the nonce, including all the mining hardware?

Just test it. For example, reduce SHA-256 into the first 16 rounds, and then try to attack your own, vulnerable nodes. Or split it into eight independent 32-bit chunks, and try to attack them, if you need some difficulty in your theoretical attacks. Or use SHA-256 eight times, and truncate it to 32-bit values, and then attack. There are many models that you can create, and then, you can see, that your question is not fully specified. It is not only in a binary state: broken vs secure. It is a spectrum, where a particular attack can harm some things, while not touching other issues. So, some attack, where you can get any value you want, just like in a modulo-as-a-hash-function model, is something entirely different, than when it would need for example 2^64 hashes to break anything.

Do you think we would need to get new wallets and migrate our funds from our old addresses?

If SHA-256 will be fully broken on preimage level, where you could say: "I want to get any message, that will hash into <thisValue>", then all OP_CHECKSIG use cases will be affected, because internally, SHA-256 is used to produce z-value. And if you skip hashing in ECDSA, then it is wide open, and you can produce a fake signature, and then create a message, that will hash into your random z-value.

However, if you worry about SHA-256, then check the current chainwork. And note that instead of trying to compute any preimage (2^256 hashes with brute force) or collision (2^128 hashes with birthday attack), it is much more profitable to produce a higher chainwork, and just overwrite the whole chain. Also, using some additional power for mining, will not remain unnoticed. There are many possible attacks, where you can harm Bitcoin, while not breaking any rules at all. For example, it is possible to raise the difficulty into some insane levels, and then just stop mining. Then, no rules will be broken, but the chain will be effectively halted, if for example the difficulty would be one million times bigger than it should be.

So, if you want to get your answer, you should clarify, which particular attack you have in your mind. Because different attacks will cause different effects, and you can test each case individually, by using some simplified version of SHA-256, with a particular weakness that you want to test, and then check only that to see, how your nodes will react. Because all you need, is just cloning Bitcoin Core, and replacing SHA-256 implementation with something else, and then running some regtest nodes, unaware of the attack, and some attacker node, that can produce hashes faster in a particular way.

[digaran]

Just test it. For example, reduce SHA-256 into the first 16 rounds, and then try to attack your own

I love it when you expect everyone else to be a genius like yourself, it's like we have the means and knowledge at our fingertips to do the things you suggest. If OP knew how to attack SHA256, he wouldn't be here asking questions about wallets.

it is possible to raise the difficulty into some insane levels, and then just stop mining. Then, no rules will be broken, but the chain will be effectively halted, if for example the difficulty would be one million times bigger than it should be.

This is one dangerous idea, thinking about it makes you wonder, what if they can use their ability to produce custom double hashes and start collecting all the mining rewards?  And when they figure out a way to break sha256, what if for years they keep it a secret and then have access to everything dependent on sha256 security?

What if they manage to reverse some transactions in the future?

If sha256 is broken, miners and ASIC manufacturers are doomed, because they will have to throw all their rigs into trashcan.
This is why independent research is extremely vital especially for bitcoin, because as we know, we are on our own, because we chose decentralization we need to keep this system safe, no government will come to rescue if something happens, they have done all they could think of to limit and restrict bitcoin adoption, if something happens, they will sit and watch with joy and smile on their face.
 

[tech30338]

Although it is possible to break Bitcoin with quantum computers still it will take hundred or more years to do that
here is what I have read but still it will take time and maybe some of us will not be around
https://cybernews.com/crypto/bitcoin-in-danger-quantum-computing-advances/#:~:text=If%20a%20Quantum%20computer%20is,before%20the%20transaction%20is%20finalized.

[digaran]

Although it is possible to break Bitcoin with quantum computers still it will take hundred or more years to do that
here is what I have read but still it will take time and maybe some of us will not be around
https://cybernews.com/crypto/bitcoin-in-danger-quantum-computing-advances/#:~:text=If%20a%20Quantum%20computer%20is,before%20the%20transaction%20is%20finalized.

Reading that article, clearly the journalist knows nothing to little about bitcoin, one could tell after reading he used private address instead of private key.

He also states what if someone mined 2016 blocks in 1 minute and left the scene? He says it would take 700+ years for difficulty readjustment, lol as if people would live their normal lives after seeing 2016 blocks in 1 min.  Of course in that case everything will change accordingly.

And if someone could mine 2016 blocks in 1 min, they could practically break sha256, so why bother announcing such capability to the world like that?

About double spending by hijacking txs from the mempool, well there is a solution, when it happens then all miners will have to accept a fork which disables RBF, so when all miners refuse to process RBF txs, an attacker no longer has the ability to double spend, there could be some implementations to record first seen txs and any tx from that address with different recipient, fee would be invalid.

Of course if miners refuse such a fork, they should start looking for something else to use their ASICs for other than mining.

While all "experts" talk about quantum computers and qbits, ECC is breakable by math, their opinions is based on current useless DLP solving algorithms, while with the right algo, you no longer need a QC.

[vjudeu]

I love it when you expect everyone else to be a genius like yourself

I am not a genius. But here we are in a "Development & Technical Discussion" board, so I can expect at least some basic knowledge about programming, because in other cases, those topics should land in some other, general discussion boards. Posting it here means that OP expects a technical response. And if you want to give any technical answer, then you have to know, how internally SHA-256 works. If you treat it like a black box, then that discussion will go nowhere.

it's like we have the means and knowledge at our fingertips to do the things you suggest

You need at least a basic understanding of hash functions, if you want to talk seriously about it. You need to know at least how SHA-256 uses internal 32-bit values, and how they are mixed in each round. If you don't understand this pseudocode from Wikipedia, then sorry, but it is just an entry level to think seriously about any attacks on hash functions: https://en.wikipedia.org/wiki/SHA-2#Pseudocode

If OP knew how to attack SHA256, he wouldn't be here asking questions about wallets.

If you ask some technical question, and you receive an answer that is beyond your level of understanding, you should not be worried about it. When I started exploring hash functions, I knew nothing about them. Then, I read this pseudocode from Wikipedia. Then I wrote a simple program in C++ to produce a single hash. Then I experimented with it, started tweaking constants, changing parameters, and playing with all of that. And then, after many months, I wrote this topic: https://bitcointalk.org/index.php?topic=5402178

As you can see, it took me many months of exploring the topic, to even think about writing something like that. And I am far from being genius or expert, because if you read, how many rounds can be broken on preimage or collision level, and if you read some PDFs, posted by mathematicians, then you will see, that my level of understanding is very basic, compared to them. I am still at round 20, when it comes to SHA-1 preimage. People went much, much further, and achieved much more than that, and I am still learning to get there later.

what if they can use their ability to produce custom double hashes and start collecting all the mining rewards?

As I mentioned, you can overwrite the whole chain, without reaching even collision level of SHA-256. You don't need "to produce custom double hashes", because it is not a low-hanging-fruit. Even if you take "broken" hash functions like MD5 or SHA-1, you still cannot produce preimages for them, you can "only" find collisions. And if you can set a million times higher difficulty, that means you can also easily overwrite the whole chain.

And when they figure out a way to break sha256, what if for years they keep it a secret and then have access to everything dependent on sha256 security?

It depends. Because as I said, it is not a "broken vs secure" game. If you can produce "a preimage", instead of "the preimage", then that kind of attack wouldn't work in some scenarios. For example, if SHA-256 is used to produce a deterministic R-value of a signature, and it is used to concatenate some private key with some message, then if you can produce "a preimage", then you would probably get a completely different (key,message) pair, and then you wouldn't know, what is the original private key, even if you can produce a valid signature for that.

What if they manage to reverse some transactions in the future?

Then they will be reversed, and those funds will be stolen. Later, they could be burned, or returned to the original owner, but any post-attack solution should be backward-compatible, and the chain should follow the heaviest Proof of Work.

Edit:

it's like we have the means and knowledge at our fingertips to do the things you suggest

Currently, you can even find websites, where you can explore SHA-256 round-by-round, step-by-step. So yes, we have that "knowledge at our fingertips", because anyone can visit https://sha256algorithm.com/ and play with SHA-256 in a browser.

[BlackHatCoiner]

And if you can set a million times higher difficulty, that means you can also easily overwrite the whole chain.

I'm just thinking of the person who could be behind that. A crypto-hobbyist, with expertise in cryptography and the like. What would he feel first after that "eureka" moment? What should they do if they prioritized the collective benefit? Keeping it secret, and never exploiting it? Publishing it, and making every mining infrastructure worth zero? What would be the best approach for that person? Maybe they start searching for past suggestions on Internet boards.  

If they start mining, that will look weird, unless they mine blocks very rarely. Otherwise, if they were to set lots of times higher difficulty, then we'll notice an unknown group of miners suddenly acquiring vast amounts of hash rate without any ASIC being sold. That will start stinking fishy.

[serveria.com]

Suppose that that there is a successful quantum attack on SHA-256. That it happened so quickly that Bitcoin has to move infrastructure with the nodes is transitioned to a quantum resistant software. What do you think would happen to the miners, the computation of the nonce, including all the mining hardware?  And by extension how would this affect Bitcoin wallets. Do you think we would need to get new wallets and migrate our funds from our old addresses?

This scenario isn't particularly realistic as first powerful enough quantum computers will most probably be owned by governments or corporations not cybercriminals. So Bitcoin devs will have time to migrate to another more safe protocol which would withstand a quantum attack.

[garlonicon]

What would he feel first after that "eureka" moment?

You can easily find it out, if you see someone that is trying to break some altcoin. Or you can feel the same thing, if you try to solve security-related puzzles, like those ones: http://www.wechall.net/ (in general, we had many people on forums, who thought that someone successfully broke ECDSA, hash functions, and things like that; they were all wrong, but their feelings were probably genuine).

What should they do if they prioritized the collective benefit?

In case of altcoins, the right way of doing that, is full disclosure on forums. Inform anyone and everyone about a particular weakness, and create a situation, where a statistical CPU owner can mount a successful attack. And then, if developers are wise, they will fix it immediately, and everyone will be safe and happy again. But if they will try to ignore that constructive criticism, then such altcoin should be burned, and all attackers can just destroy it. I saw that many times on bitcointalk, there are whole groups that collect a lot of Bitcoins, just by finding and destroying half-baked altcoins, which are full of security holes.

Keeping it secret, and never exploiting it?

This is bad idea. That means, someone else will just discover the same thing, and it will be worse, because the coin with that weakness will reach higher values, and more people will be harmed, when it will be destroyed in the future.

Publishing it, and making every mining infrastructure worth zero?

This is never the case. First, as vjudeu mentioned, it is not "secure vs broken" game. There is always some particular attack, and your defense will depend on that particular attack. Look at hardened SHA-1. Why it was created? Because of backward-compatibility. How it was created? Of course, based on the attack from 2017. If that would not happen, and if we would have a different attack in 2023, then hardened SHA-1 would use a completely different algorithm, designed specifically for that 2023 attack.

What would be the best approach for that person?

Exactly the same, as with every other security issue. First, write to the developers, inform them, give them some time to fix it. And if nothing will happen, then reveal everything publicly on forum. If it is still not sufficient, then demonstrate a practical attack on some test network, if there is any. And then, if messed up testnet is ignored, attack the mainnet. Because you revealed everything, and reached every previous stage of "inform and wait for the fix", you can publicly, and openly attack and destroy everything, to bring all of us into a world, that is safer, and resistant to this particular attack. Because if you won't, then that coin will grow further, and collapse in a worse way in the future.

Those steps in the middle can vary a little bit, but the general approach is simple: contact with developers, give them some time, and then publish it in a full disclosure model. You can find a list of previous BTC issues, and see, how exactly they were submitted in the past, how they evolved, which of them are solved, and which of them are still wide open, and wait for the future solution: https://en.bitcoin.it/wiki/Common_Vulnerabilities_and_Exposures

Edit: https://www.youtube.com/watch?v=4k1GcX1cqMg

[Setvin]

Has anyone ever thought that "quantum computing" (as we are being sold it, destroyer of worlds) might just be complete pseudo-science?

Should we sit around debating what will happen when the first mining farm discovers free energy?

[philipma1957]

Just test it. For example, reduce SHA-256 into the first 16 rounds, and then try to attack your own

I love it when you expect everyone else to be a genius like yourself, it's like we have the means and knowledge at our fingertips to do the things you suggest. If OP knew how to attack SHA256, he wouldn't be here asking questions about wallets.

it is possible to raise the difficulty into some insane levels, and then just stop mining. Then, no rules will be broken, but the chain will be effectively halted, if for example the difficulty would be one million times bigger than it should be.

This is one dangerous idea, thinking about it makes you wonder, what if they can use their ability to produce custom double hashes and start collecting all the mining rewards?  And when they figure out a way to break sha256, what if for years they keep it a secret and then have access to everything dependent on sha256 security?

What if they manage to reverse some transactions in the future?

If sha256 is broken, miners and ASIC manufacturers are doomed, because they will have to throw all their rigs into trashcan.
This is why independent research is extremely vital especially for bitcoin, because as we know, we are on our own, because we chose decentralization we need to keep this system safe, no government will come to rescue if something happens, they have done all they could think of to limit and restrict bitcoin adoption, if something happens, they will sit and watch with joy and smile on their face.
 

What if diff is 200t it is the year 2040 and miners simply realize ltc/doge algo is far superior due to Doge never lowering its 10000 coin reward.

Doge is progressively lower % wise in inflation every year but always has a decent reward level for miners.


This threat above is greater than any other. Miners are the value bodyguards for a coin.  They will simply follow profits.  Much more threatening than a 'special' computer cracking address and taking fund out.

[stwenhao]

ltc/doge algo is far superior due to Doge never lowering its 10000 coin reward

There is a topic about tail supply, good luck: https://bitcointalk.org/index.php?topic=5405755
Also, there is another topic, which popped up more recently: https://bitcointalk.org/index.php?topic=5466502
Which means, there are many better places to discuss it, than this topic.

[philipma1957]

ltc/doge algo is far superior due to Doge never lowering its 10000 coin reward

There is a topic about tail supply, good luck: https://bitcointalk.org/index.php?topic=5405755
Also, there is another topic, which popped up more recently: https://bitcointalk.org/index.php?topic=5466502
Which means, there are many better places to discuss it, than this topic.

we can argue quantum threat and the implications and one implication is

a quantum miner can increase the diff to 1000t vs the 55t it is now.

it is 2040 and btc diff has jumped to 1000t.

China has quantum mining in effect. as they developed a 200ph miner that uses 3000 watts.

just like they tore the top off btc rally in April 2021 they do it in 2040

they drop the diff down from 1000t to 100t the blockchain effectively freezes

and miners have to switch to a non quantum algo say scrypt with the ltc/doge stuff set up and ready.

Btc may not recover from that type of attack as it involves quantum only inlplace on the sha-256 mining Asic.

title of thread mean what effects can a quantum pc do to btc.

so a twofold attack would be trash btc sha256 and offer a replacement  algo scrypt

this is a two prong attack which needs quantum pc mining and a replacement algo

I suppose btc would need to alter its algo in an immediate move and the alternate would need to be an in place working algo. that has a lot of gear.

It would be a true mess.
Another way to fight a difficulty attack could be an emergency difficulty adjustment.

[digaran]

Bitcoin on it's own will survive any attack, even attacks such as rewriting the whole chain, because it's a distributed ledger, whatever happens people won't simply say Ok this experiment was fun, now that it's under serious attack lets just forget about hundreds of billions and move on to a new experiment, No there will be lots of bankruptcies and thousands of lives will be destroyed but it will rise from the ashes, because "decentralization" is what they signed up for, meaning no central crisis management organization (unit) will step in to handle the situation.

Problem is with mining machines, any new algo, solution should be based on one thing; whatever developers and manufacturers do, they need to make it compatible with current infrastructure in place, because if I am mining and suddenly they pull the plug and say you no longer can use these miners because there was an attack, well what am I supposed to do now?

Of course the usual answer is, "developers will fix it don't worry", developers can't keep their wallets safe, how can they keep a giant network safe when it's under attack?
(We knew these risks when we signed up for Bitcoin.)