Bitcoin Forum

There may be a temporary bitcoin recovery, but it is doomed long run b/c it is not quantum secure. IBM wll have a QC of 4,000+ qubits by 2025 (in two years). It takes only 1556  qubits to break the ECDSA encryption used to correllate private to public keys. What this means is if you have an exposed (unhashed) public key - which if you ever used your wallet it leaves an unhashed copy of your public key out there on the network for anyone to have - a quantum computer of 1556 or more qubits can take that public key and reverse engineer out your private key. Game over. Bitcoin has no value other than as a way to Secure information - security is literally its only selling point - when that security breaks, as it will, it has no more usefulness and the value will crash to probably just a few dollars, propped up by die-hard dead-ender BTC maxis. If you want to get rich on bitcoin, short it by buying a short bitcoin etf (example is ticker BITI - not financial advice). Doing anything else will result in losing investment.

Google this / do your own research - this is not "FUD", this is just sober fact. Bitcoin public keys can fall with QC's of just 1556 qubits. (Source: https://security.stackexchange.com/questions/33069/why-is-ecc-more-vulnerable-than-rsa-in-a-post-quantum-world ). Misinformation you hear is that it takes many qubits to crack RSA hence bitcoin is safe - this only relates to the bitcoin mining algorithm not the ECDSA algorithm used to relate public/private keys which is more vulnerable. Again - in 2 years or so IBM will have QC strong enough to reverse engineer private key from unhashed public key. When this happens panic will spread and bitcoin will crash. This is as predictable as the housing bubble collapse of 2008 and just like then, there are people who will shout "FUD" at anyone showing the plain and simple facts. Don't be on the wrong side of this.

How much quantum computer will cost and also I doubt that this kind of one of a kind computer will be use just to hack a certain wallet while it can be easily tracked on where will the token be send via blockchain.

I’m Bitcoin security will evolve if there’s a threat like this in the future.

Do you have any other suggestions other than selling and exiting the market? people with access to Quantum Computers have more concerning issues than just hacking Bitcoin addresses, with the probability of breaking the encryption of strong algorithm, other important things are at stake, like military related encrypted data.

I am not a trader though I am a developer and have worked at a manager level in a cryptocurrency company in the past so I know what I am talking about (I like to hope lol) from a technical standpoint. So I am here to warn about technical vulnerability but cannot give financial advice - there is a short bitcoin ETF (BITI) I have heard about (I am not invested in this myself, again I am not a trader, I just do boring old 401K / index funds lol) so that may be one way to profit, by shorting bitcoin, but again not financial advice.

The point is, in today's internet world, secrets don't stay secret for long. I am sure IBM would not knowingly let its system be used to hack bitcoin, but if they can build such a system, others could - say a state actor like China / North Korea. Yes of course a quantum computer could be used to hack other things too and it probably would - but if you were China (say) you could make millions / billions even, shorting bitcoin if you knew you could take it down, and I am sure they have already thought about this. Also, it is not just about money, it is an ego thing for them - they would love to take down bitcoin in order to stick it to the USA and the West.

And even just these possibilities may be enough to spook the market. Think about it - it is not needed for a country like say North Korea to use a nuclear weapon in order to cause concern - just the fact that North Korea Has a nuclear weapon means we have to take them seriously and try not to provoke them too much. Similarly, just the fact that a system to take down bitcoin *could* be built and used by bad actors, is enough to cause concern and cause ppl to get out of the bitcoin market, causing a crash. So just the existence (in 2025) of a 4000+ qubit machine by IBM (code-named "Kookaburra" - google it) could be enough to crash bitcoin market (because, again, it only takes 6 * 256 qubits, 1,536, to take out ECDSA encryption and allow someone to guess a private key based on the corresponding public key).

Again , not financial advice, I am not a trader and don't care about that. I do care that too many ppl are taking too big risks they cannot afford and they don't understand these risks. Maybe bitcoin will replace ECDSA with a quantum-safe algorithm and I hope they do. But right now they haven't even started on that and they are basically like the Titanic going full steam ahead, ignoring all iceberg warnings. So this is my iceberg warning as a former developer / manager in this space - get to the lifeboats while there is still time. :)

How confident are you of your nonsense?

Are you willing to put your money where your mouth is?

I suggest a bet.  We both put up some amount of money. Then, 2 years from today, if the exchange rate is less than 50% of today's exchange rate, you get the money. Otherwise, I get it.

Just think, since you're SO sure, this is an easy way for you to guarantee a 100% return on your money!

Or, are you just spouting nonsense and FUD?

If the bitcoin developers see a risk in bitcoin by quantum computers they will do something about it, you really think people will just seat and watch how bitcoin dies? that will not happen.

And even if it happens there is always the option of a hard fork to recover the lost coins on the attack. So, I don't thinks quantum computers will destroy bitcoin, when those computers get enough power to attack bitcoin then BTC will be strong enough to avoid it.

Weird and the timing though, this is the second time that I have seen another quantum computer thread, this is the first one,  Breaking RSA Encryption with Quantum Computer (https://bitcointalk.org/index.php?topic=5433605.0/). Is this the new FUD attack since the price of bitcoin is going up to the $21k'ish?

And there are a lot of threads as well in the past that discussed about this so called QC and what's it's effect on bitcoin and any other technology that relies on ECDSA encryption.

There have been countless threads in the past tackling this very issue that you're so worried about. If bitcoin is not secure against quantum computing, then developers can just move it to a more quantum-resistant algorithm that will at least put up a defense against quantum computers. A lot of pro-bitcoin developers are into this solution, although of course it will not be easy given that we first much reach consensus before major changes are done into the code.

2 years is a pretty short time to give finality on something that has been resistant to most brute-forcing attacks in the past decade.

I don't know much about technology, and I also heard about QC that can break bitcoins, but I don't believe it to be true. I do not believe that our developers will stand still and do nothing and wait for QC to come to destroy bitcoin, QC is developing, and Bitcoin also developing.
And when it comes to Fuds, you're probably right, I suspect that Fuds is being spread on our forums rather than sending us a warning. In just 1 day, there are 3 quantum topics.
https://bitcointalk.org/index.php?topic=5434765.0

So that gives us two years to come up with abwuantun resistant protocol, thanks for the heads up, although I think the perceived threat is farther off than that.

There has always been an inherent risk of quantum computers making it possible to derive private keys from their public keys, and this risk has always been a topic of discussion, meaning solutions to it would also be readily available when that time comes.

I found many topics about Quantum computers and a first topic was created in 2012. Quantum computer and Bitcoin (https://bitcointalk.org/index.php?topic=133425.0).

A most informative topic about that is I don't believe Quantum Computing will ever threaten Bitcoin (https://bitcointalk.org/index.php?topic=5157696.0). OP can read it before discussing more.

I am no longer fearful about Quantum computers and their risk to Bitcoin cryptography after reading it.

Bitcoin and quantum computing is an old story, as others have pointed out. Is there any evidence that a powerful enough quantum computer is so close to being real? To me, it's more like a low risk, something where we might suddenly get a breakthrough, but that's unlikely. Sometimes a wall is hit, progress unexpectedly slows  down in an area for many decades. Just look at space exploration and how "far" we've moved since 1960s. I believe that quantum computer that will have enough power to pick a private key is likely to become something like humans on Mars: seemed so close in the second half of previous century, and we're still far from it.
Moreover, security isn't Bitcoin's only selling point. A big point is decentralized form of digital money with fixed supply and open access to mining coins.

I totally agree. Every time I read something about quantum computers it looks like they are being developed just to disrupt bitcoin, that's pretty much the only thing they're useful for. No one ever mentions all the other risks such as military information, national security, nuclear codes, power plants, etc. It's an interesting way to see things.

i dont agree with their timescale. but its healthy to get into practice, early.. .. just in case

"bitcoin" is not vulnerable(in a sense where idiots think bitcoin is overall broke.. (reality: ITS NOT!))

quantum cant compete in regards to the ASIC hashpower of the blockchain(sha)
what is "at risk" is some p2pk utxo's

by using p2pkh or other formats your unspent funds are safer,
(quantum cant really do backward engineering on the ripemd160 hash or sha)

 but just dont re-use address after you spend(PK key is revealed)... put any 'change' or future funds to a new address.

that said. its not like quantum will reverse engineer in 0.1 seconds. it takes time still. which is a slight deterrent so the more you own on a address the more caution to ensure you "spend" correctly.
(they wont waste hours of a billion dollar machine to steal coffee amounts)

debit cards and other banking systems are more at risk..
EG debit cards are not as easy to change your bank account in minutes. but with bitcoin you can use a different address per spend(few minute exposure risk)

The points are and continue to be:

1) It's a lot of FUD by people who either don't understand so are posting nonsense or who want to spread FUD

2) People who don't realize that breaking BTC is so far down on the list of people who would have access to this kind of tech that it's basically not on the list. Breaking government encryption and banks and RSA and all the rest would be higher up on the list.

3) What franky1 said about p2pk utxo's

4) The cost of doing it in would be more then what you would get.

5) It's been 2 years away since 2013 or so....

-Dave

There is still a significant amount of work to be done with qauntum computing before it can be considered to be a credible threat to blockchain technology.
it will take upto 5 to 10  years to develop 4000+ qubits
in that much time
We may will find a quantum proof way of using bitcoin or developing QT proof technology

While some blockchains were designed to be quantum resistant and will survive the rise of quantum computing in their current form , like iota etc.

quantum computer would need thousands or even millions of qubits to break modern cryptography, but currently, they have less than 100 qubits.

blockchains may can be upgraded as long as all the miners or validators who are running the network agree to implement the upgrade . While blockchain upgrades are extremely rare due to disagreements from independent miners or validators, quantum resistance will be a matter of life or death for blockchain technology.
There is no rational excuse for any miner or validator to refuse a quantum resistance upgrade when the threat of a quantum attack becomes possible.

I suggest to read this :
https://eprint.iacr.org/2021/967.pdf

Everything that has level 1 access security will be vulnerable to quantum computers in the future. Social networking sites, and anything that requires 1 step verification like for instance, cryptocurrency wallets will be at risk of breach and compromise. But think of it this way, surely, when the future comes around and quantum computers become publicly available, there will be measures taken by the IT sector of our future to alleviate and maybe even prevent such attacks. They may even do so before commercially opening the use of quantum computers in the future because let's face it, everyone knows this is going to be a problem. themselves included. So there's no way they wouldn't figure stuff out before implementing such powerful tool.

If they could hack bitcoin then they could hack the banking system as well as the government which uses the same underlying technology as bitcoin to secure their customer funds. You think the big banks and government are going to allow that to happen? Modern society and the totally computerized economic system as we know it would collapse.

Every year for over ten years you always hear someone screaming about quantum computers hacking bitcoin, and it's only two years away.
But they said the same crap 10 years ago LMAO.

@cafter With respect, it is incorrect that it will take "5 - 10 years" to develop a 4000+ qubit machine. IBM will have one in 2025 (two years from now), making P2PK public addreses (which are not hashed) vulnerable as I said above. So not all of bitcoin will be vulnerable, true, but plenty of it will be, especially because since Taproot, the real unhashed public keys are left exposed after making a transaction so it is correct that the stop gap solution if one is using bitcoin is not to reuse public address, but this does not address the economic / market issue of loss of confidence that would occur if even one P2PK address were compromised. So this is why it is negligence of the highest order for the BTC devs to be continually dismissing this real problem as "FUD" when it would be an easy matter (a soft fork) to replace ECC with something like a hash-based algorithm which is more secure. Just absolute irresponsibility on the part of the bitcoin leadership.

Source that IBM will have 4,158 qubit machine in 2025 (and they have since 2017 always hit their quantum computing roadmaps, so it needs to be taken with the upmost gravity): https://spectrum.ieee.org/ibm-condor

That is true, before it is getting deployed for public consumption, they already know what to do in terms of security protocols.
It is not that they will just let it out in public without thinking of anything about its impact to security aspect.
There are so many computer or tech geeks, who would willingly work on this potential drawback using quantum computers.
They are not just sleeping on this possible issue. And before we know it, they already come up with tangible solutions.

https://ibb.co/pyJLmX0

Ok, so ibm

sorry , i not included it i researched about other companies like google , intel etc.
But there is "may" also , so let's see what happen's

I'm far from technical but from what I read somewhere in the (near) future quantum computers will be a thing and their capabilities will keep on increasing. So per definition it will become a threat sooner or later to crypto.

I also read Bitcoin protocol will be updated to protect it from these attacks. How would that conceptually be possible ? The only solution imo would be to make the private key more complex ? Would be impossible no ?

Again not technical and only using my basic knowledge so don't attack me :)

Our current era CPUs are only 64 bits. Why no upgrade to 128 bit CPUs?

This upgrade would be trivial and easy to implement, as it would entail merely increasing the byte length of registers. So why have 128 bit CPUs not yet emerged?

Likewise with ASICs. If it is possible to increase cryptographic function on chips, simply by extending the bit length of registers. Why have we not seen ASICs with registers that can hold a bazillion bits?

Think of engines in cars. If exotic luxury cars are known for their V-12 engines. Why not produce V-24, V-36 and V-48 engines if the goal is to produce greater horsepower and torque?

Can it be said that, at a certain point, simply adding bit length to chips and cylinders to engines produces diminishing returns.

There are two reasons for it in peoples minds. One of them is exactly what you said, the returns are not greater there and in order to be greater they are working on it as much as possible and we do get better tech here and there when someone figures how one thing works out.

However, another side says that "they are building them, but not sell them just yet so the previous ones are sold" so basically it's possible but they want to first sell the previous generation stuff and then promote the newer one. I am not saying either is the case, I wouldn't know, I am not really the person to listen to in this case, but I can say that these are the two reasons I have heard.

I don't think that hacking bitcoin address or wallet is very easy before someone might have done that I believe that the person have practice city in different ways and is not majority people that we can involve insult out of hacking bitcoin address because if that is possible many people would have lost their bitcoin wallet so from my understanding I don't think that is very easy for someone to hack a bitcoin wallet

Bitcoin and quantum computers, that's pretty much an old topic, and have already discussed them many times. Many people are very stressed about quantum computers because they think if the time comes up that would be really easy to crack a bitcoin wallet by using a quantum computer, while the thing is even if a quantum computer tries to crack it still the cost of a quantum computer won't be reasonable and in the other hand I'm sure even after investing these quantum computers these devices won't be available for everyone to start attacking other people, so there is still nothing to worry about.

cars:.. there is a certain point where adding more torque doesnt make the car go any faster, but instead rips the axel from the frame. you stop gaining more acceleration and instead end up just getting mis-fires and stalls and engine cracks.


CPU's work in binary. there is only a certain scale needed to perform certain tasks in proceeding steps of needed bits before its not really needed to use more bits per operation

what then becomes the efficiency is multl-tasking side by side.. rather than one after the other/tandum
this is where asics work better using multiple chips rather then one super chip

because asics work in just binary and hex. there is only a certain amount of processing of particular bytes needed
if you look underneath the code at the binary movements. the sha process is in allotments of 32bit form

check out https://sha256algorithm.com/
notice each W allotment is broke up into 32bit lengths

there is no need for 128bit if the "messages" are broken up into 32bit lengths of a 512bit message

however having multiple attempts(chips) performing their own attempts side by side, this then multiplies the efficiency

here is the thing
when it comes to cryptographic puzzles
breaking up a 512bit message  from 32bit.. to instead say 128bit. is foolishly like changing from a 16 piece jigsaw puzzle into being a 4piece jigsaw puzzle. thus it has the opposite effect.
512bit message handling 4 pieces of 128bit becomes EASIER to reverse engineer compared to
512bit message handling 16 pieces of 32bit

https://pbs.twimg.com/media/FZBhpREXEAEUj8i?format=jpg&name=900x900
If you take a look here, this is a comparison between the top 500 supercomputers versus the Bitcoin network over the time since Bitcoin was created at the year 2009.

For me, we must not be worried at all about super computers because, for me, it is impossible to happen that the Bitcoin network will be compromised, market cap speaks here, those billion of u.s. dollars that are already in the Bitcoin market cap will not be there if Bitcoin network is vulnerable.

sha is safe.
dont worry about PoW algo and asics.

the risk is in the ecdsa of keys. and learning that bitcoin does have mechanisms to protect from quantum. but people need to learn how to use them

dont put funds onto a address that has exposed its public key
this means not using p2pk (yep satoshi stash is are risk of moving)

accept finds on p2pkh or newer formats. but when you spend it. dispose of that wallet/address.

dont re-use an address to receive funds after spending funds from said address
use different destinations for "change"/remaining funds, that are not the same key as the one you spent from before

---

if you are worried about when sending out a unconfirm broadcast to the network and before confirm a quantum sees your relayed broadcast, reverse engineers the key and he RBF's your tx to replace it with their own tx with a different destination.. dont worry.
though quantum could reverse public-private its not a 0.1sec task. its a multi hour task..
the real risk is those hoarding funds on used addresses or addresses with public key exposed. where by just sitting on funds for hours/days gives them time.

In the world where ChatGPT is taking over the computing I highly doubt that Quantum computing should be your first choice. Also there is no way quantum computing will be able to solve the bitcoin related algo because we don’t need that kind of hashing. Neither it will be worth it to brute force with quantum computing power. It is going just very well the way it is right now. The seeds generated are literally garbage they mean nothing so there is no point of using such high powered cpu to worn on it.

Are you trying to create FUD or whatever?
 To program a Quantum computer it cost up to $500,000 or more,  so what would the hacker gain spending such amount of money just to hack Bitcoin?, Meanwhile such amount of money could be used to even make more money, putting it into investment or even use it to Buy Bitcoin.

 In the other hands, the Quantum computer that you're talking about is created by someone and not spirit, same hand tech guys will find way to get Bitcoin more encrypted if that be a threat.

However, I don't think that Quantum computer will be a threat to Bitcoin's security rather it will Augment it and even make Bitcoin's security even more stronger Imo.

forget hacking "bitcoin"

instead think.. bruting #4 on bitcoin richlist
Balance: 124,347 BTC 2,635,389,906 USD
https://bitinfocharts.com/bitcoin/address/1LQoWist8KkaUXSPKZHNvEyfrEkPHzSsCd

that said the topic is FUDing timescales and misunderstanding the differences between EC and RSA

Give me a mathematician, a cryptography engineer and a quantum computer, I will brute force that address in a few weeks. Problem with finite numbers of private keys is that you just need enough computational power to crack a cerain key, there is also no need for knowing a public key etc, it's just pure science.

that address is already a re-used address, so its ripe for the pickings(PK exposed). more so than satoshi's block 9 re-used address, more so than average joe only hoarding sub 1btc per address

Owners of four million Bitcoin (BTC), or 25% of all BTC, are susceptible to a quantum computer assault because they reuse BTC addresses or use public keys that have not been hashed.

If you think seed phrase can be easily broken by quantum computing or brute forcing, you need to know how long it will take just for hack 6 words, while right now a non custodial wallet at least have 12 words, while hardware wallet have 24 words. It's really impossible to crack it, at least for the next 10 years. But I'm sure many Bitcoin's contributors will keep update and create a proposal to increase the Bitcoin security when there's a new threat happen in the future.

I forgot 6 words from my seed, any brute force tool ? (https://bitcointalk.org/index.php?topic=5279690.msg55311284#msg55311284)

As pointed out by many users on this thread, and over the years they wouldn't be bruteforcing the seed. Bruteforcing is literally the least efficient way of breaking anything, and the seed isn't exactly the weak point. Whether or not you believe quantum computers will be a realistic threat to Bitcoin, you've got to acknowledge that we'll probably have to change in order to defend against the possibility. Now, that's absolutely years from now, and no where near the two years that HomerF_48 suggested.

Now, I'm not concerned since I know that the changes have a long time to be thought over, and the changes that are necessary will be made way before quantum computers become a realistic threat. Also, just because a quantum computer could be developed to attack the ECDSA, doesn't actually mean that's what it would be used for. It's not like your common criminal will have access to a quantum computer.

I think changes would be pretty easy as well. Just the fact that we turned from legacy into segwit is the proof that we could still change some things if it helps the bitcoin world, right now I spend just a dollar or less for any transaction, it used to be as high as 30-40 dollars to do that.

If we are so capable of changing something that will help, and 85%+ of the users suddenly all decide to move? That means many many years down the line (I agree it won't be 2 years) when quantum is a real threat to us, then we will make it even harder, and we will make it as long as it could get, and seeds will be safe, not like they will be attacked, but we can still defend nevertheless.

Expert criminals/ terrorists such as US/ China governments, already have their prototypes. They are the main concern.

Most of the sig campaign participants seem to fear the developers, since they hold power around here, so they'd just go with the usual script saying all is fine and the "devs" know what they are doing etc. Yeah, like the dear security expert aka Luke knew what he was doing in regards to his own security!

alot of people think that "cracking" cryptography means its deemed a success when they can manage to crack a key in seconds
this is not the case

even cracking a millenia length normal attempt in just one year is treated as success
(many crpytography cracking competitions win the award if they can crack a millenia+ normal pc effort cryptography in a year or less)

where by to then bring that year length down to 6month, 3 month, 45 days 3 weeks 1.5 weeks 5 days, 2.5days, 30 hours 15 hours 7.5 hours and so on down to being just a few seconds.. actually requires multiplying the system of the year long success by many multiples

its not a case of if they can break it in a year with XXXXqubits they just need to add a couple more qubits.

its actually to have hundreds of QC computers of XXXX qubits each
which if it costs $1b for one QC then it costs hundreds of billions for hundreds of QC systems

yes bringing the efficiency down from millions of years down to 1 year is an achievement. but then that method is tapped out and becomes a multiplier game. equipment and of cost.

so if your fearing a QC will reverse engineer a public key in seconds when they announce they broke ECDSA to compute a key in a year.
calm yourselves

It's sad to see newbies on this forum talking shit about Bitcoin, I bet OP is here to spread FUD, people like you don't have any Bitcoin in their wallet 'if they opened any', why don't you just worry about how you will get your hands on a quantum computer and start using that to jail break people's bitcoin wallet? I want to see how far this can go for you. For now it's 100% FUD, if you don't have anything sensible to say please just stop.

Huh, even if there was some bad stuff going on, Satoshi himself did not imply the Core developers could hard fork the Blockchain into a quantum resistant protocol from what it could be considered to be the last "honest block"?

The only problem would be the transacions done after the first attack and there could be some loss of funds if the honest block has much age. Such scenario could impact negatively the ecosystem for some time.

The OP thinks that the world richest people who are investing in bitcoin are ignorant of the fact that quantum computers will be treat to bitcoin. This is not the case. Everyone knows that quantum computer will not be able to decode the bitcoin keys.

Think in a layman way that since the interest in bitcoin is not getting less and world money is getting into bitcoin shows that quantum computers may not be a threat to bitcoin.

I would suggest OP not to spread the fud especially on this forum.

IIRC, I've read the same thoughts when I was still new in the market like for someone who's new to it, will definitely discouraged from that statement about quantum computers.

Well then the panic has been said and effective to me during that time. Someone who's not experienced yet in the market might fall for it.

But when you study just the history of bitcoin, are you still going to believe with it? And are those quantum computers will just have to focus on bitcoin and as they say crack it down and won't do something else that are more important?

I am done with this stupid argument and claims that quantum computers will be the end of btc. Quantum computers are not near the qubit requirements to challenge the algorithm that btc uses and probably will not be there for many years. When that happens we can have a amnesic blockchain or find another solution that will prevent quantum computers from attacking public keys. It will require a hard fork but everyone who cares about btc will want this to happen. People will lose their coins especially if they are inactive for years. Satoshi coins will be lost but they would be lost if we did not make the change anyway. Reusing addresses will probably not exist in the future or will not be enabled by default and will only be enabled by people choosing to reuse a address. Wallet software will be rewritten to cycle addresses and to allow transaction to the same addresses in a wallet without it exposing the public key. There are a lot of solutions some of them still being refined that can protect us against quantum computers when they eventually get good enough to threaten btc.

the 2 years that op says is bullshit and I think op does not understand the difference between quantum computers not all quantum computers are the same. Quantum computers are designed for a certain task and the task of breaking encryption will probably be one that will be developed because it is useful to the military but it will be a race to who gets it 1st and it will not be useful after everyone knows it exists because they can protect against it when it is a real threat. btc will not be the 1st target and I do not think it will be a target. We are low priority and a quantum computer that can break the algorithm can break many other algorithms that military and governments use so it will be a big deal. But the op is full of bullshit because the governments will be the 1st to protect against this and there has been no major developments in years. This is FUD and should be ignored but there is some truth that quantum computers will probably be a threat sometime in the future but a long time from now.

I think it's inevitable that at some point in time something will break ECDSA.. I mean there's a pretty good incentive to find a solution to it so is a matter of when and not if.  QC or not.  The issue is how does cryptocurrency (and every other crypto related sector) survive.  It's pretty easy in my mind, it's no different than that bug where billions of bitcoin were printed once upon a time... it's a hard fork where new code fixes the issue.

So here's how I'd see it playing out.

Assumption 1.
Most likely it's the public keys in the chain that get compromised first as that's a lot easier than P2PKH style transactions where you need to derived a private key and script that matches the hash.

Assumption 2.
It takes a period of time to do P -> k solution (i.e. > 10mins).

With those assumptions we would likely get early indications of a compromise.  Early satoshi coins move, large accounts compromised to move the market, etc..
An update to the chain could be put out that offers a new signature system. 
If the attack is convincing that either a QC or fundamental crack has happened, a certain block number (even in the past) could be used as the reset point.

Everyone who wants to adopts the new hardfork.  Yes we have the BTC/BCH rubbish again but this is part of the bitcoin evolution process.  Strongest mining is 'the bitcoin' chain, so only through decentralised concensus is that reached.

Next anyone who wants to spend from an OLD tx has to also provide some PoW on their provided signature.  This means a simple GPU running for say a day does enough PoW to state they are the owner of the signature.  This would prevent even a compromise or QC attack from spending everyone's coins since they'd still need to do PoW for every tx they try to steal.

I'm sure there are even better ways to approach this but my approach is not to worry as we can always rollback and be inventive even on the worst possible attack imaginable.

Quantum computer issue is created to FUD the Bitcoin market.  To put a hindrance on Bitcoin adoption by spreading false and exaggerated information of quantum computers.  The way they say how Quantum Computer breaks Bitcoin security is like Bitcoin development will be idle and wait for these QC to crack its security algorithm.  Developers will adjust the security algorithm of Bitcoin when they feel that QC is catching up. 

So I never think that quantum computing is a threat to Bitcoin security even if Bitcoin security development has stalled for half a decade.

This seems to be a bit FUD

Well post quantum cryptography is going to evolve too. Developers aren't going to be stagnant and lets be honest, quantum computing still has a ways to go before it gets anywhere close to posing a threat to the bitcoin algorithm, or any encryption system for that matter. People expect about a decade or so. But the existing quantum technology is by far very experimental currently, and not that much of a threat to any encryption algorithm, so we are safe for now. And I expect quantum-resistant methods to be out before quantum computing can actually break these algorithms.

In fact, there are many articles COINTELEGRAPH article on quantum threats (http://"https://cointelegraph.com/news/why-quantum-computing-isn-t-a-threat-to-crypto-yet") detailing approaches that are already in progress that want to mitigate the quantum threat - many aided by big corporations with a lot of funding. This is just how cryptography has always worked, someone tries to break the encryption system while others keep designing countermeasures.

Even if this is true, and quantum computers will not be able to threaten cryptocurrency for a long time, anyway, information about this should not be immediately labeled as FUD. It is better to prevent the negative impact on the cryptocurrency from quantum computers than to watch the market collapse for years later. Theoretically, quantum computers can crack the secret keys of cryptocurrency, the only question is their power, and they are constantly and quite successfully working on this. But I don't see any real work to counter such negative capabilities of quantum computers. Just brush it off because it can't be, it's clearly not an option.

It looks like people here have bought into the hype. Don't buy into the hype. We need fewer people to talk about overhyped things like GPT, quantum computation, and artificial intelligence because these people have a lot of things to learn. Buying into the hype is very annoying. Since you have bought into the hype, you have probably been oblivious to other technologies related to quantum computation. Do you know about reversible computation? Reversible computation is the computing technology of the future, but the media has not hyped reversible computation. There is absolutely no reason for this other than anti-intellectualism. I therefore refuse to take anyone who talks about AI alignment or quantum computation seriously unless they are familiar with reversible computation and realize that reversible computation is at least as practical as quantum computation.

Quantum computation can help with some specific problems, but reversible computation will replace all forms of computation. Since reversible computation is more feasible than quantum computation, reversible computation will affect the cryptocurrency ecosystem before quantum computation does.

If you think that quantum computation will allow us to solve some exptime problems in a reasonable amount of time in just 2 years (well, now 1.5 years), then you have bought into the hype. If you have also not even heard of reversible computing, then you have not been properly informed about the future of computational hardware.

Let's pretend that a QC powerful enough now exists to break ECDSA within 10 mins.

Let's put on an "attacker hat" and see how it plays out...  

It's very unlikely an institution would do this due to it being illegal and the fine/lawsuits would ruin a company.  Therefore a single staff member is most likely to use a company's QC to attack the network... a bit like how people used to use company computers to mine with and later get caught.

The weaker, older "pay to public key" transactions would become the first victims.  Whilst this could include Satoshi's first minted coins, it's unlikely they would attack those early coins since any movement of long stored 50BTC tx's will always alert people.  Instead they'd focus on the most recent P2PK tx's and work backwards in time.

* Grab a P2PK tx and obtain the private key.
* Write down with pen and paper.
* Wipe or obscure the operation from QC history.

Manually construct the tx to another address, go to a coffee shop & VPN.. publish tx to a public home run node.
repeat, slowly and accelerate as getting more cocky that they got away with it.

So how is Bitcoin protected after such an attack?

This is the hardest part, we can't hard fork fix this since we wont know what is genuine and what is done by the QC.

Best fix I can think of is addressing the issues...
1. Add a quantum resistant signature system to Bitcoin
2. Require PoW for any transaction submitted to the node.

Ideally step 1 should be done now.   We don't need to use this new signature system but it should be ready to swap to.
Step 2... at a point when QC is believed to have compromised bitcoin, we require PoW of CPU power before accepting a transaction.  The transaction must pay to a QC resistant tx.
The PoW should be significant but not too much.  E.g. 1 hour's worth of PoW of the hash(nonce + signed TX).
The result of the PoW could be put in an OP_RETURN call or even a new OP code.

This way it becomes expensive for an attacker to steal too many coins and valid owners can use their laptops or mobile phones to issue transactions.

Hard to see how this would be rolled out in practice but P2WPKH happened so if there is a demand it could well be done.

Yes, if you are planning to use a quantum computer for real life mining then you are in risk. 
 
If you want to get rich it takes a long time to do so, it also depends on the user and the price you intend to buy. For the long term you are in a bear market and this is a high risk so you may be in the red and it will likely happen.

This make me remember a quantum blockchain project that's already trading om exchnages, I have been monitoring the project for a while and when I asked the team if they can provide any evidence that they are in possession of any quantum computer they ignore my message and when I reply saying that I will keep asking this question over and over they block me off their telegram group.

Quantum computers? It's so far in future, probably will never be possible, trust me, we can't even provide lower power-consuming chips for our daily computers from Intel and AMD you are talking about quantum computers. 

Do not fool yourselves, there is a reason why the fastest CPU still can't mine a Bitcoin today and that's because of software support and also high mining difficulty, I will wait for 2025 to see if there will be any quantum computer been released. We shall see..