Quantum computers: possible menace to Bitcoin?

[GODLIKE]

Imagine somebody buys one of these and turn it on mining.

This would bring the next increase in difficulty to hell, so much that the cost for mining would disrupt any income for anybody.
Nobody would mine anymore, apart maybe the owner of the quantum cpu.
That brings us straight into the 51% danger, right?

A quantum cpu may not be economically cunning AT THE MOMENT, but when the Bitcoin value will grow, the cost of a quantum cpu could be well worth the cost.
Or imagine a central bank that wants to destroy Bitcoin: just buy one of these and fuck up everything in one week.

[jjdub7]

This has been addressed a number of times.

https://bitcointalk.org/index.php?topic=133425.0

As I understand, if the threat ever emerged, the devs would have enough time to hard-fork to SHA512d as the hashing algo in a worst-case scenario.  Hashing itself isn't effected, but the infrastructure supporting the network could be.  The quantum CPU would also have to have enough scalable RAM to perform the computations necessary to bruteforce the entire network, the tech for which is 50+ years away.  Plus the cost would become insurmountable, especially once mining chips reach the 10nm architectures and beyond, which is expected to happen in the next decade.

So no, not really a threat AKAIK.

[DannyHamilton]

What a waste of words.

It took less than 10 seconds with a Google search engine to turn up the following:

That is not true.  Quantum Computers need an efficient quantum algorithm.  Shor's algorithm is very effective at brute forcing public key systems (RSA, DSA, ECDSA).  They don't significantly reduce the security of symmetric (AES) cryptography or hashing algorithms (SHA-256).

Hashing functions are effectively immune to the potential of quantum computing.  Shor's algorithm can not be used against hashing functions or symetric cryptography.  

To say quantum computing is "advancing rapidly" is an overstatement.  In 2001 the largest number to be factored by a general purpose quantum computer using Shor's algorithm was 15.  By 2011 the largest number to be factored was 143.   That is from 4 bits to 8 bits in the span of a decade.   We are a long way from factoring even 256 bit numbers and 256 bit ECDSA keys are even harder (~3,072 RSA key = integer factorization).  

Nobody said 256 bit encryption will be secure forever.  It is infeasible to brute force a 256 bit key using classical computing.   Quantum computing may someday break it but it may not, quantum decoherence is a bitch.  It is possible ECDSA has some flaw and cryptanalysis will someday weakened it to a point it is economical to attack it.  That could be next year or not in the next century.  

Did you put any effort at all into figuring out if your FUD had any merit before you came running to the forum to declare a "menace" that has already been discussed dozens of times over the past 5 years?

[GODLIKE]

This has been addressed a number of times.

https://bitcointalk.org/index.php?topic=133425.0

As I understand, if the threat ever emerged, the devs would have enough time to hard-fork to SHA512d as the hashing algo in a worst-case scenario.  Hashing itself isn't effected, but the infrastructure supporting the network could be.  The quantum CPU would also have to have enough scalable RAM to perform the computations necessary to bruteforce the entire network, the tech for which is 50+ years away.  Plus the cost would become insurmountable, especially once mining chips reach the 10nm architectures and beyond, which is expected to happen in the next decade.

So no, not really a threat AKAIK.

Doh I didn't expect somebody would have thinked of this already, sorry  

But I can't understand one thing: you hard fork to SHA512 and difficulty increases for everybody, where's the solution?

Thanks for the link, I'll read that.

[GODLIKE]

What a waste of words.

It took less than 10 seconds with a Google search engine to turn up the following:

That is not true.  Quantum Computers need an efficient quantum algorithm.  Shor's algorithm is very effective at brute forcing public key systems (RSA, DSA, ECDSA).  They don't significantly reduce the security of symmetric (AES) cryptography or hashing algorithms (SHA-256).

Hashing functions are effectively immune to the potential of quantum computing.  Shor's algorithm can not be used against hashing functions or symetric cryptography.  

To say quantum computing is "advancing rapidly" is an overstatement.  In 2001 the largest number to be factored by a general purpose quantum computer using Shor's algorithm was 15.  By 2011 the largest number to be factored was 143.   That is from 4 bits to 8 bits in the span of a decade.   We are a long way from factoring even 256 bit numbers and 256 bit ECDSA keys are even harder (~3,072 RSA key = integer factorization).  

Nobody said 256 bit encryption will be secure forever.  It is infeasible to brute force a 256 bit key using classical computing.   Quantum computing may someday break it but it may not, quantum decoherence is a bitch.  It is possible ECDSA has some flaw and cryptanalysis will someday weakened it to a point it is economical to attack it.  That could be next year or not in the next century.  

Did you put any effort at all into figuring out if your FUD had any merit before you came running to the forum to declare a "menace" that has already been discussed dozens of times over the past 5 years?

Cool down, kid.
I didn't declare anything, you may have missed the question mark in the very title.
You want to say I don't know stuff: that's right.
You want to say I didn't search: that's right too. I wrote I didn't imagine somebody thought about this already. My fault.
But forums are here to spread info, also.
Now if you are annoyed of spreading info, just don't do it.

[EtherCoin]

Anyway, by the time quantum computers are available for the public, all bitcoins have already been mined...

Do you think quantum's will be ready for the next 5-15 years? no way...

Eth.

[Lauda]

The same questions being asked over and over by newbies.
No, relax, nothing will kill bitcoin.

[balanghai]

Anyway, by the time quantum computers are available for the public, all bitcoins have already been mined...

Do you think quantum's will be ready for the next 5-15 years? no way...

Eth.

The next question would be. How would quantum computers do if they can make it next year(Economically)? Spend million bucks for a handful of BTC? And then what? One could gain BTC efficiently by buying it. Using Quantum Computers doesn't seem logical.

[GODLIKE]

Anyway, by the time quantum computers are available for the public, all bitcoins have already been mined...

Do you think quantum's will be ready for the next 5-15 years? no way...

Eth.

As I wrote, you don't need to have them available to the public: a big institution could want use it to destroy the Bitcoin system, and we know banks aren't waiting for anything else.
And yes I think quantum cpu will be available to big companies in the next 10 years.

[GODLIKE]

Anyway, by the time quantum computers are available for the public, all bitcoins have already been mined...

Do you think quantum's will be ready for the next 5-15 years? no way...

Eth.

The next question would be. How would quantum computers do if they can make it next year(Economically)? Spend million bucks for a handful of BTC? And then what? One could gain BTC efficiently by buying it. Using Quantum Computers doesn't seem logical.

Imagine that on October of 2015 1 BTC will be 100000 $.
You can't know it.

[Elwar]

Simple answer.

No

[GODLIKE]

Simple answer.

No

ARE YOU A GOD?
/

[techlover]

Quantum computers are still ideas, it will take decades to become true.

[jonald_fyookball]

The same questions being asked over and over by newbies.
No, relax, nothing will kill bitcoin.

we need a more comprehensive FAQ to avoid repeating same educational points.

[Ron~Popeil]

Even when they are available  they will be prohibitively expensive for quite a while. If they would ever be a threat the developers would have ample time to address it.

[hollowframe]

Anyway, by the time quantum computers are available for the public, all bitcoins have already been mined...

Do you think quantum's will be ready for the next 5-15 years? no way...

Eth.

The next question would be. How would quantum computers do if they can make it next year(Economically)? Spend million bucks for a handful of BTC? And then what? One could gain BTC efficiently by buying it. Using Quantum Computers doesn't seem logical.

Just to play the role of devils advocate, what if something were to happen like the professor that was banned from using the supercomputers? One could simply "borrow" a quantum computer to mine bitcoin for some temporary period without paying anything.

[Ron~Popeil]

Anyway, by the time quantum computers are available for the public, all bitcoins have already been mined...

Do you think quantum's will be ready for the next 5-15 years? no way...

Eth.

The next question would be. How would quantum computers do if they can make it next year(Economically)? Spend million bucks for a handful of BTC? And then what? One could gain BTC efficiently by buying it. Using Quantum Computers doesn't seem logical.

Just to play the role of devils advocate, what if something were to happen like the professor that was banned from using the supercomputers? One could simply "borrow" a quantum computer to mine bitcoin for some temporary period without paying anything.

As was pointed out above quantum computing would not be a very efficient way to hash.

[GODLIKE]

Anyway, by the time quantum computers are available for the public, all bitcoins have already been mined...

Do you think quantum's will be ready for the next 5-15 years? no way...

Eth.

The next question would be. How would quantum computers do if they can make it next year(Economically)? Spend million bucks for a handful of BTC? And then what? One could gain BTC efficiently by buying it. Using Quantum Computers doesn't seem logical.

Just to play the role of devils advocate, what if something were to happen like the professor that was banned from using the supercomputers? One could simply "borrow" a quantum computer to mine bitcoin for some temporary period without paying anything.

As was pointed out above quantum computing would not be a very efficient way to hash.

I can't understand why you say this.
For the little I know, quantum computing should empower cpu by 1000 of times.
Maybe we still don't know how to code with qubits?

But apart this, I can't see how a qubit, that can be in many superstates at once, can't be a much more efficient way to hash away numbers.
It should be super efficient exactly in that, because it would make many more tests per second than cpu with 0-1 bits.

[jonald_fyookball]

Anyway, by the time quantum computers are available for the public, all bitcoins have already been mined...

Do you think quantum's will be ready for the next 5-15 years? no way...

Eth.

The next question would be. How would quantum computers do if they can make it next year(Economically)? Spend million bucks for a handful of BTC? And then what? One could gain BTC efficiently by buying it. Using Quantum Computers doesn't seem logical.

Just to play the role of devils advocate, what if something were to happen like the professor that was banned from using the supercomputers? One could simply "borrow" a quantum computer to mine bitcoin for some temporary period without paying anything.

As was pointed out above quantum computing would not be a very efficient way to hash.

I can't understand why you say this.
For the little I know, quantum computing should empower cpu by 1000 of times.
Maybe we still don't know how to code with qubits?

But apart this, I can't see how a qubit, that can be in many superstates at once, can't be a much more efficient way to hash away numbers.
It should be super efficient exactly in that, because it would make many more tests per second than cpu with 0-1 bits.

Probably because hashing is a very straightforward, mostly arithmetic process.
Quantum computing functionality needs to be combined with quantum algorithms
in order to enjoy greater speed than classical computing.

[EtherCoin]

At this point, and unless something amazing happens, I still think that quantum computers are way far away to affect bitcoin.

In the case that in 10 years, any government or high power institution could put their hands in a superquantum computer, they could destabilize a bit the economy perhaps... but at that point the remaining of un-mined bitcoins will not represent the same risk as if it would happen right now.

My .00000002 BTCs

Eth.