Bitcoin Forum

 I have been reading about quantum computing and it's ability of putting the whole blockchain at "risk" , some "paid" articles seem to address quantum computer as the end of BTC and blockchain technology in general.

 The ugly part is that they only address these "potential" security threats to bitcoin and not to cryptography and encryption in general.

 so after reading a variety of articles and papers of where some would say that QC is the end of bitcoin while some other's think of QC more like a unicorn.

 i found this research paper

https://arxiv.org/ftp/arxiv/papers/1711/1711.04235.pdf

which seems to me by far the most accurate yet the simplest of which i have read.

if you are interested in knowing about the potential risks to bitcoin i suggest you spend sometime reading the paper, you sure as hell will learn something new.

In my opinion Quantum Computers are far away from being in the hands of a person with malicious intentions. First, its estimated costs are $15-$25 millions just to have such a computer. Second, if you are a 'bad guy' and buy a quantum computer to disrupt the Blockchain, it's more likely everyone will know that it was you. There are 11 Quantum Computers currently owned by google, IBM, some university and other organisations.
I just hope for the best of bitcoin. Anyway thanks OP for this awesome paper that I saved.

https://en.bitcoin.it/wiki/Quantum_computing_and_Bitcoin

It's not clear whether quantum computers large enough to attack Bitcoin will come into existence in 10 years or 100+ years. If the former, then making Bitcoin quantum-safe in a hurry will be messy, though it can and will be done.

It's certainly not the "end of blockchain technology". Anyone who says that doesn't know what they're talking about. Designing a quantum-safe cryptocurrency is trivial, though it adds significant overhead, which is why nobody's really doing it yet. QRL claims to be a functioning and remarkably efficient quantum-safe cryptocurrency (though still much less efficient than quantum-unsafe cryptocurrencies), but I haven't looked into any aspect of it very much.

We already know Bitcoin is partially secure against QC, mainly because :
1. In ECDSA you need public key to get private key, which mean you should be safe if you never re-use address
2. SHA256 isn't vulnerable against QC^[1]

Also, we could change from ECDSA to quantum-resistant signature.
BTW, there's thread with similar topic at https://bitcointalk.org/index.php?topic=5087640.0 (https://bitcointalk.org/index.php?topic=5087640.0), you might want read that thread as it contains information you might want to read.

Source/more info :
1. https://crypto.stackexchange.com/questions/59375/are-hash-functions-strong-against-quantum-cryptography-and-or-independent-enough (https://crypto.stackexchange.com/questions/59375/are-hash-functions-strong-against-quantum-cryptography-and-or-independent-enough)
2. https://arxiv.org/pdf/1804.00200.pdf (https://arxiv.org/pdf/1804.00200.pdf)

A few other coins promote themselves on the bases of being quantum-resistant ( i don't like to use the word "safe" because it's a very inaccurate IMO) .
but you are right in terms of clarity that concerts the the efficiency of quantum computing and it's ability to harm blockchain technology, given the current data we have at our disposal , it's more like a unicorn. but still i see nothing wrong with improving bitcoin if the treat appears.



"Grover's algorithm makes it a "much easier" to brute force a hash function by using only the square root of evaluations as apposed to current/classical 0/1 computing. while a square root of something may seem like a lot of reduction , but it latterly means nothing when you trying to brute force something which is 256 bits long. "