What does Quantum Computing mean for Bitcoin?

[paulie_w]

Simple question, and I am by no means well-rounded in my knowledge of quantum computing. But what I have read indicates that it is a massive hammer to all crypto algos currently in existence. Could the sudden existence of quantum computing mean the sudden uselessness of Bitcoin as a currency?

[kiba]

If we invent quantum cryptography, business will continue on.

Otherwise, everybody's secret in the world can and will be cracked.

[grondilu]

Could the sudden existence of quantum computing mean the sudden uselessness of Bitcoin as a currency?

Yes.   But pretty much also for everything you consider safe on the internet.

[cardinalshark]

My brother-in-law is a physicist very involved in the world of research on quantum computing and I just asked him this question last week. All modern secure computing uses encryption based upon the same principals and if QC becomes a reality, all modern secure computing becomes insecure.

He thinks QC is a boondoggle and it reminds him of the government funded fusion research. A big money effort to something that may never happen and we are not even close.

If QC came into existence, he said we could use QC to encrypt and make this encryption impossible to crack by QC. And of course, the only 100% impossible to break encryption is one time pads.

[grondilu]

If QC came into existence, he said we could use QC to encrypt and make this encryption impossible to crack by QC. And of course, the only 100% impossible to break encryption is one time pads.

Indeed, with QC we won't use DSA, we'll just use quantum cryptography, which will be much better than prime numbers based cryptography.

I guess it will then be easy to create a quantic cryptocurrency.  Is there a quantum computing version of proof-of-work ?

But anyway so far this is just science-fiction.  We might as well talk about space tourism to Alpha Centauri.

[kwukduck]

QC doesn't just magically break all crypto, it makes it a lot easier possibly by several magnitudes,but many things could still be considered 'safe' for daily use.

[jib]

QC doesn't even magically make all crypto easier. There's a quantum algorithm for fast integer factorisation, and for a few other things, but there are also classical public-key systems which aren't known to be broken at all by QC.

I expect if it looks like someone's getting close to building a quantum computer, a lot of effort will go into the development of these systems. Making Bitcoin QC-safe might just be a matter of replacing our public-key cryptography (ECDSA) with something else.

[grondilu]

Making Bitcoin QC-safe might just be a matter of replacing our public-key cryptography (ECDSA) with something else.

Easier said than done.

[em3rgentOrdr]

Making Bitcoin QC-safe might just be a matter of replacing our public-key cryptography (ECDSA) with something else.

Easier said than done.

We will have to keep secrets by not sharing them...

[jib]

Easier said than done.

Yes, it's nontrivial, but it could be done. My point is that QC wouldn't be the end of Bitcoin, and that we might be able to defend against it without having any quantum technology ourselves.

[Ryo]

The "something else" has to be something that quantum computers are not better at solving than classical computers. Quantum computers do not magically make P=NP, so there are still be problems where solutions are hard to find but easy to check, even with cheap quantum computing everywhere.

[chaord]

Perhaps with quantum technology it will be feasible not only to keep bitcoin alive, but to build a better bitcoin along the way.  For example, fully homomorphic encryption has recently just been shown to be possible, yet it is too slow for production use.  Perhaps something like that would be incorporated into the "next generation" bitcoin, thereby making bitcoin transactions verifiable, yet untraceable.

[kiba]

Somebody needs to write an article series on cryptography.

[Ryo]

Somebody needs to write an article series on cryptography.

I'm currently working on a series of articles explaining the concepts used in Bitcoin, like proof-of-work and hashes. I would have to study a little bit before fully understanding exactly what quantum computers can do.

[hazek]

http://www.bbc.co.uk/news/science-environment-12811199

Quantum computing device hints at powerful future

One of the most complex efforts toward a quantum computer has been shown off at the American Physical Society meeting in Dallas in the US.

[wb3]

To answer the question: Not much. The BitCoin would just get to the 21 Million quicker.

But lets take a look at what would be needed. Considering this is an area that I am, what one could say, familiar with.  First we need ternary hardware, Russia kind of had the lead in this, and still have a few ternary computers around.  Basically it is hardware that is designed on 3 states not 2 or -0+ instead of 0101. One could run the logic on a binary system, but you loose the advantage of a ternary system. Guess who gets to use it first, The Government but hey they paid for it.  This actually start with University of Pennsylvania a long time ago. MIT has some musings on the subject.   

So the BitCoin would be safe in Quantum Computing, Hashes however, will be pretty useless. Just create a new key pair for each transaction, and get two or more confirmations, then it wont matter if the hash is cracked. It will only matter if you use the same Key pair for multiple transactions, meaning that they could crack your key pair.  But with PKC using Quantum Computing to generate Key pairs then you could just scale the system to keep the Odds of a crack off the charts.

How about using Quantum Pairing for sending and receiving between parties, instantaneously (even between Planets) and completely untraceable to boot.

A P2P Mesh network based on Quantum Pairs. Oh, baby. 

[rikur]

There's always stuff like http://en.wikipedia.org/wiki/Unbalanced_Oil_and_Vinegar

[hazek]

What does Quantum Computing mean for Bitcoin?

Nothing, at least until Quantum Computing transcends from realm of myth to reality.

Did you read my post??

[hazek]

Of course there's nothing wrong with your logic except that it's irrelevant since we're almost past it and doesn't contribute to the topic discussed at all.

[Ian Maxwell]

I don't think quantum computing is going to come out of left field. Many of the people paying attention to Bitcoin are heavy into crypto and will have a good idea of whether there's a major advance coming up.

Once it seems that quantum cryptanalysis is a real threat, all of these folks will start moving their money out of BTC and into other areas. And at least a few of them will be interested in inventing "Qubitcoin." Once that exists, smart money will move to Qubitcoin. Once folks notice the sudden inflation, even dumb money will move to Qubitcoin. A few slow movers will likely be left holding the pieces.

I'm curious about whether a Bitcoin-like currency could be minted with intrinsic value, so that even those last few won't be totally empty-handed. Encoding some sort of useful information that can only be accessed with the private key? But really I don't think this is anywhere close to the biggest threat to crypto-currency.