Topic: Quantum Computer vs Bitcoin - page 6. (Read 2502 times)

I recommend the following to anybody seriously interested in understanding QC:

- https://arxiv.org/abs/1312.4455 --> "The Universe as quantum computer" by Seth Lloyd, professor of mechanical engineering and physics at the Massachusetts Institute of Technology.
- https://www.youtube.com/watch?v=dEaecUuEqfc --> "The Quantum Conspiracy: What Popularizers of QM Don't Want You to Know" by Ron Garret

Lloyd argues that quantum physics tells us that the universe is indistinguishable from a quantum computation. This is a powerful meta-argument for the perennially fashionable idea that we're inside a computer - but Lloyd argues convincingly that it's a quantum computer.

Garret explains that a lot of the popular conceptions about quantum mechanics are not only incorrect, they are locked onto pernicious misconceptions that are simply false. He throws light on the phenomena of entanglement, quantum randomness, among others. In short, Garret's approach is to look at QM through the lens of QIT (Quantum Information Theory). Combined with Lloyd's thesis that we are inside a quantum computer, this gives a "post-Simulation Hypothesis" interpretation of QM. The behavior of quantum particles is only "weird", "strange" or "bizarre" because we're using the wrong metaphors (tiny billiard balls). Nobody expects the bits in a classical computer to behave like classical particles because, obviously, bits are not particles. But, if Lloyd is right, quantum particles are ontologically informational, just like classical bits.

Consider the question: Where are the bits that encode the letter between the single-quotes? ---> 'q'

This question has no correct answer. There is no "where". Copies of the letter exist in several locations, ephemerally scattered throughout the memory of your computer, the memory of the computer that served this webpage to you, and so on. Under Lloyd's thesis, this fact is related to the fact that we can end up getting nonsense when we ask a question like, "Where is the quantum particle that ____?" Garret convicts QM popularizes of contributing to mysticism in the public about the solid facts of quantum physics.


Yeah, most of the Bitcoin FUD is ridiculous but the quantum FUD is particularly hard to stomach.

The seeds are run through a KDF (key derivation function) which uses iterated hashing.  I am not qualified to say definitively whether a quantum computer could efficiently attack those; and I should know better than to even hazard a guess, without really thinking about it for a very long time.  But my gut says this would probably not be a profitable attack.  Now, watch someone else show me up here...

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There is a pernicious little subcultural strain of arrogant doofuses who enjoy spouting “skepticism” of quantum mechanics.  Put that aside; of course, they’re morons—and all the moreso, when they make Internet posts using computers which could not be built without the practical application of quantum mechanics.  Rather like Flat Earthers who use GPS.

There is a huge difference between that, and skepticism of quantum computers.  A quantum computer is not a sure thing!

I should preface this by saying, I’m not endorsing the opinions of Scott Aaronson.  I’m only citing him as someone who is not a moron, and wrote a book on quantum computing (which I have not read).  I seem to recall some wager on his blog over the (im)possibility of quantum computing, but I can’t find it right now; anyway, D-Wave has a long history (2013) of drawing his ire (2017), to say the least.

See how he discusses skepticism of quantum computers:


Though he’s not a good speaker, an interesting lay-level talk is “What Quantum Computing Isn’t” (August 2017).  At 09:39, he notes, “The trouble is, if you want it to be useful, well, at some point you’ve got to observe your computer, you know, to read an answer out.  And if you just measure, you know, the superposition of all answers, not having done anything else, the laws of quantum mechanics say that what you’re going to see will be a random answer.  Okay?  Well, if you just wanted a random answer, then you could have picked one yourself, with a lot less trouble.  (Audience laughs.)”  Funnily enough, at 12:55, “QUANTUM BITCOIN” appears on the screen on a slide discussing Silicon Valley Startup “QUANTUM” buzzwords.  He does say of quantum computing that “it’s not science fiction” (13:15), when discussing Google’s 22-qubit chip; near the end (14:17), he says, “Already within a few years, we may achieve what I think of as the number-one application of quantum computing, which is just to disprove the people who say that it’s impossible.  (Audience laughs.)  Could it be impossible for some deep reason that nobody has figured out yet?  Well, of course.  But in some sense, that’s the more exciting possibility.  Because that’s the possibility that means we have to rewrite all the physics textbooks.”

Aside, just to cut through some more of the quantum hype:

djb derides the alleged physical security of quantum cryptography (PDF) (“Is the security of quantum cryptography guaranteed by the laws of physics?”  djb’s answer seems to be “hahaha!”).  (To be clear, quantum cryptography is a different matter than quantum computing.)  He has also attacked the motives of quantum computing and quantum cryptography researchers (“How quantum cryptographers are stealing a quarter of a billion Euros from the European Commission. #qkd #quantumcrypto #quantummanifesto”).  Hmmm.

As for myself, I account myself moderately skeptical of quantum computing; I’ll believe it when I see it, but meanwhile I think it’s a good idea to move to PQ crypto.  I would be more surprised if quantum cryptography can deliver on its promises.  I don’t like the hype around any of it, especially when it’s sometimes used to FUD Bitcoin.

You must be tripping heavy to live in that imaginary world. The quantum theory as well as the quantum computer both are real and working.
D-Wave was the first company to officially build a quantum computer. You can read it out on Wikipedia here https://en.wikipedia.org/wiki/D-Wave_Systems . Also Google and NASA are joining hands to build a quantum computer which would be much powerful and can solve a problem 100 million times faster than a standard computer.
Take a read about it here : http://www.popularmechanics.com/technology/gadgets/a18475/google-nasa-d-wave-quantum-computer/

You're mad bro, this thing exist. you need to read it here http://www.wired.co.uk/article/d-wave-2000q-quantum-computer Quantom does really exist but it cost a lot of fortune in it.

Yes, that's exactly what I was asking about, thanks!

Indeed, this part:


got me confused a bit, since I'm not very familiar with ECDSA.

But I think my question can be repeated for wallet seeds: how long would 128 bit seeds be secure against QC, and how do you think Bitcoin community will react if/when someone will start claiming coins from those wallets that were considered to be lost (I'm assuming that most holders will move their funds to new wallets before quantum brute force will become feasible). Of course it's a far smaller threat than the complete failure of public key cryptography, but still I'm curious.

Are you speaking of this page?  It is wrong (permalink to incorrect section in incorrect version).  I will apply for wiki editing privileges to correct it.  A Bitcoin private key is always exactly 256 bits, no more and no less.  I infer that the editor who wrote the incorect text was confusing private keys with HD seed values, or something of that nature.  On a brief glance, this page and this page seem correct.

Others on this thread have already explained the basic technical details of what a quantum computer could do.  The takeaway is that Bitcoin’s public-key crypto would be broken—however, public keys which have not yet been exposed would be safe.  There is no way to recover the public key from its hash, not even with a quantum computer.  For other hash properties, in a PQ world, a 256-bit hash should be considered to have today’s equivalent of a 128-bit security level; that’s adequate.

The more important point is that a practical, real-world quantum computer would shatter the banking system, as well as the security of the whole Internet.  Bitcoin would actually fare relatively well, due to its use of hashes in transaction outputs.  This is not really a Bitcoin issue.  Some people (not you) who ask about quantum computers in this context tend to imply that it’s a Bitcoin risk, whereas you should be (relatively) much more worried about your bank accounts.

I've read on the Bitcoin wiki that Bitcoin private key is usually a 256 bit number, but it can also be between 128 to 512 bits. Does this mean that someone with a quantum computer can theoretically generate all 128 bit long private keys in 2^64 time using Grover's algorithm? Also, is there any way to check if an address corresponds to a key of certain length? So, if such attack is possible, how likely it is to be executed on practice (how likely early quantum computers will be able to break 64 bits of security) and what can be done to prevent it?

All cryptography will be threatened by this, not just bitcoin.

Yes it's possible but in fact is a very long process, it can not happen before year 2027/2028.  Bitcoin uses secp256k1 cryptography that can not be hacked today, and when this will be possible using Quantum computers I am sure Bitcoin will be ready and have the quantum fork for quantum resistance cryptography standard,
right now there is one proposal already now called qBitcoin.
https://spectrum.ieee.org/tech-talk/computing/networks/qbitcoin-making-bitcoin-quantumcomputer-proof

Not fake at all. In fact, the computer you are using would not be able to operate without specifically quantum effects - the semiconductor effect (field effect) is itself a result of the quantum behavior of properly doped silicon. Without this quantum phenomenon, we would not have solid state electronics and our computers would all be running on vacuum tubes - a computer equivalent to a TI calculator would require megawatts of power to operate.

You can directly observe quantum phenomena for yourself with a helium discharge tube and a diffraction grating - you will see spectral lines (emission and absorption lines) which contradicts the classical theory of light. An even easier experiment is to layer a couple polarization filters and a polarity rotation filter to "erase" the effect of one of the filters using quantum erasure. It's a simple experiment that anyone can do and you will directly observe quantum erasure in a way that contradicts your intuition about the way that the filters should behave.

Fools who think replacing science with math somehow makes for legitimate concepts...and after a google search followed by a link to wikipedia, we can rest assured you're all experts on quantum mysticism. haha

There are a couple errors, here. First, 2^x (EXP) is way harder than x² (P) - a computer that could solve 2^x problems wouldn't even have to break a sweat to solve x² problems.

In theory, quantum computers (QC) can store information exponentially in the number of qubits - 20 qubits can store a megabit (2²⁰ classical bits) of information. But the exponential space advantage of QC does not necessarily translate to an exponential time advantage. QC has a quadratic time advantage for search problems vis-a-vis a classical computer.

Your sarcasm was straight to the point
Scientists nowadays are:
"Hey this should be researched, I need a lot of funds"

We're going back to "Earth as the center of the solar system" in the field of "Quantum" physics because of these kind of researchers.

OP: Looking at the current development in Qcomputing, Quantum computers will not be a threat to Bitcoin. There are more threaths than that to look after.

If yes, that quantum computer can impose threat to bitcoin and other crypto currencies, it then means that not only with the shutting down of the internet will be the threat of crypto currencies.

good answer. I would add that a QC could  mine blocks way faster using something similar to Grover's algorithm

Don't worry too much. Read more technical materials and you will see the quantum computing is not good at the decryption in the crypto currency.

If i'm right, Quantum Computer is best for solving exponential problem (2^x) while Bitcoin cryptography either based on polynomial (x^2) or/and Elliptic-curve/ECDSA (y^2=x^3+ax+b), so bitcoin security won't affect much by Quantum Computer. CMIIW.

Why do you think of the destruction of Bitcoin while you could have made the same thread for increasing the efficiency of Bitcoin through quantum computers. Quantum computers do exist right now but I don't think they will be able to destroy the efficiency of Bitcoin. The current quantum computers are obviously more developed than electronic/digital computers but are not so well developed that they can crack any private key. To destroy the functionality of BTC  not only a super quantum computer is need but also the algorithm to break the BTC's code. It will at least take a few decades to build such a super quantum computer to achieve this thing and by the time it is possible BTC would have been far more developed seeing it's growth right now.

May I ask the wise ones whether quantum computer can be used to increase the efficiency/development of BTC in some way ?

As said, quantum computing isn't magical. It's really not difficult to create 5000 nodes right now, even.

While its true that Bitcoin nodes are the backbone of the network, you cannot technically destroy the whole network. The only thing sybil attack (the most damaging IMO) can achieve, is to isolate people from the network. This could potentially allow attackers to execute a double spend attack on them and tricking them to see confirmations that they don't actually have. That isn't easy either. You will need to generate valid blocks and also have thousands of IPs which a quantum computer has no advantage of.

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Quantum computers can weaken ECDSA but that doesn't mean private keys can be cracked instantly and without cost.

Security agencies and the US DoD have tech that is at least 30 years in advance of the stuff you buy on Amazon. Quantum was likely put into production for breaking RSA 2048 in the 1990's, which is why they stopped making such a big fuss. The fact that publicly available crypto is allowed to be freely shared should tell you it's all broken.