Quantum computers to crack SHA256 - when will that become reality?

[Codroipo]

A fork would be a solution

[Katewind]

I think this issue will not happen in the future because The Blockchain Developers have many tools to prevent this crack in the near future.
Do not worry about that . just go and buy come bitcoins to hold them for long-term period as future investment .
I guess it will be at 3,000 usd in this year.

[U2]

Stupid post.

NO! Quantum computers aren't magic you moron. Rather than computing with 1's and 0's (or bits) they use sequences (qubits). They just aren't binary. This is completely useless for trying to crack encryption. Why the hell would this help at all? This is like trying to use an asic to play a video game. You need a damn GPU! Both are powerful in their own way but are 100% useless for doing the other task.

Go ahead and lock the thread now. Maybe you should do a quick Google.

https://en.wikipedia.org/wiki/Quantum_computer

edit: and if some some crazy magical unicorn pixy dust out of your ass way something cracked SHA-256, online banking would also be hacked. I have a feeling the hacker would be going after the trillions of dollars/euros etc rather than ... $20Billion worth of bitcoins. Who gives a crap about bitcoins in this instance??

[Karartma1]

I think this issue will not happen in the future because The Blockchain Developers have many tools to prevent this crack in the near future.
Do not worry about that . just go and buy come bitcoins to hold them for long-term period as future investment .
I guess it will be at 3,000 usd in this year.

blockchain developers... 

[metokr]

I think it is not possible .

[Silberman]

In theory, Quantum computers should already be powerful enough to crack SHA256.
If I had created a QC, this is one of the first tests I would perform.
At least thats what I understand from websites such as DWave.
Only 2 QBits would be enough from what I understand, unless someone is telling big fat lies (or we still cant code for the Quantum realm)
I know nothing about it to be perfectly honest, with the exception of the claims being made by these companies that create Quantum computers, which seem to be very big indeed!

Never get your information from the source that builds or has an interest in the subject, just look at robots, artificial intelligence and all of that, those things have been one generation away for a long time and there is no reason to think we are even close to get hard AI.

[Shiroslullaby]

This is a topic that should definitely be a sticky in the Technical Discussion section.
The same question gets asked literally every two weeks. Topic could be closed and OP pointed to the sticky,
at least until there was some further information on this subject.

[KeyGenKing]

Well, years could be possible yes.
China is on his way to do this
http://www.pcworld.com/article/3194574/hardware/china-adds-a-quantum-computer-to-high-performance-computing-arsenal.html
But to crack the SHA-256 i don't think so.

[Blinken]

If I knew, I would not post that information to a public forum.

[Come-from-Beyond]

SHA256 doesn't need to be crackable to bring Bitcoin to knees:

4.3 Resistance to quantum computations
It is known that a (today still hypothetical) sufficiently large quantum computer can
be very efficient for handling problems where only way to solve it is to guess answers
repeatedly and check them. The process of finding a nonce in order to generate a
Bitcoin block is a good example of such a problem. As of today, in average one must
check around 2^68 nonces to find a suitable hash that allows to generate a block. It
is known (see e.g. [13]) that a quantum computer would need Θ(√N) operations to
solve a problem of the above sort that needs Θ(N) operations on a classical computer.
Therefore, a quantum computer would be around √2^68 = 2^34 ≈ 17 billion times more
efficient in Bitcoin mining than a classical one. Also, it is worth noting that if
blockchain does not increase its difficulty in response to increased hashing power,
that would lead to increased rate of orphaned blocks.

Source: https://www.iotatoken.com/IOTA_Whitepaper.pdf

[drawingthesun]

Can Quantum computers one day break SHA256, and hence cause Bitcoin's death?

When would that be estimated to happen?


(probably won't die since we'll hard/soft-fork then to a new algo or smth, but just for discussion's sake)

Could quantum computers be a problem?

These people think so: https://theqrl.org/

[swogerino]

If a Quantum computer can already crack the SHA256 algorithm then we are all doomed here. There is no future for bitcoin if someone is able to crack it, no matter who this someone is. Since Quantum computers are mostly in the hands of the governments which don't like bitcoin , they would have already used it to crack bitcoin and to end it.

I think for the moment this is not possible and is the hope that for a lot of years this will not happen that keeps us going and  to believe in bitcoin strength.

[QuartzBlockchain]

This topic has been discussed multiple times already. Please use the search function or google and read up on the subject.

There are no known ways that quantum computers will break sha256.

Exactly. Also remember that in the event of a super power quantum computer trying to break the sha256 hash they will need however to compete with the majority of miners together which secure the network by definition. It would be a fail cause I think that noone can override the power of a peer to peer network of such capabilities as the one of Bitcoin in the future when this kind of attack could happen.

[Come-from-Beyond]

Can a full-scale quantum computer revert SHA256? No.
Can a full-scale quantum computer own Bitcoin blockchain? Yes.

Nothing to discuss below this point, IMO.

[digaran]

How do we know that right now the available quantum computers aren't mining Bitcoin?
What else would be more profitable to do for them? aren't the current QCs perfect for mining?
What happens if a QC was in fact mining Bitcoin but before the difficulty adjustment stopped?
And started again after the target has passed?

[liputin]

what about decentralized super computers? elastic xel just showed POC where elasticPL mined bitcoin block.

POC video can be found here: https://vimeo.com/216378462

update can be found here: https://bitcointalk.org/index.php?topic=1396233.msg18910971#msg18910971

[ImHash]

what about decentralized super computers? elastic xel just showed POC where elasticPL mined bitcoin block.

POC video can be found here: https://vimeo.com/216378462

update can be found here: https://bitcointalk.org/index.php?topic=1396233.msg18910971#msg18910971

You said it your self "supercomputer" not quantum computer, you could also call ASICboost machines as a super miner.
Since when mining is a crime? no matter with what kind of hardware you are mining as long as you don't skip the work
Only concern about quantum computers is about their ability to crack down the prime number sequence and find private keys not what if they were mining bitcoin.
Already IBM/ DARPA/ Google and US have their own QCs but still in early stages of development, they are now more like the 30 years ago mobile phones which people used to call them bricks because they were big and heavy.

[dinofelis]

Can a full-scale quantum computer revert SHA256? No.
Can a full-scale quantum computer own Bitcoin blockchain? Yes.

Nothing to discuss below this point, IMO.

Well, if full-scale quantum computers are used in mining, they would simply "up" the difficulty, in the same way that the introduction of ASICS did.  You would have miners with quantum computers "competing" for blocks and all the rest left behind, like the CPU miners were left behind by ASIC miners.

Of course, the problem with PoW as a cryptographic security mechanism is that it is a quite ridiculous "security" in the sense that the work to be done by an attacker is comparable to the work done by the "good guys" ; and in the case of technological evolution, the work to be done by an attacker is MUCH LESS than the total work done by all the good guys (work done as in economic cost of work done).
For instance, with ASIC miners, it is very easy to overdo all the work that miners did the first few years of bitcoin, for much less cost than these miners did spend on it.
So if ever there is a quantum computer that can mine, miners should use it directly, and the "old part of the chain" will be easy to redo with the quantum computer at hand ; but competition between quantum computers will still make the "head" of the chain ; like ASICS now make the head of the chain, but the old tail is relatively easy to do over.