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Ask HN: If Quantum computing wins, Blockchain then dies, right?

11 points by somid3 ↗ HN
Given today's news of IBM's quantum chip and the myriad of other quantum-related news out there, it seems all Blockchain technologies will be susceptible to be hacks and will inevitably fail -- correct?

16 comments

[ 3.0 ms ] story [ 48.2 ms ] thread
ghazak
Not necessarily - the software could be upgraded to take the existing chain, and upgrade it to a quantum resistant hash prior to any damage being done.
somid3
Yes, but then non-quantum devices will take forever to execute a trade.
lbradstreet
If that's true, third party middlemen with quantum devices could work around this until it becomes more mainstream. At least it would allow it to not wither on the vine until everything is restructured. It's not really obvious what would happen in any case, but humanity has a way of papering over things.
somid3
Ok. I just wouldn't want to bear that risk and have a dime on any public-digitally-signed protocol. Let alone my savings.
jotux
If quantum chips work out then a ton of existing financial infrastructure using non-quantum-resilient security will also fail.
savethefuture
There is already a dependency between capabilities in trading (esp. high freq trading), things will adapt. Fear not.
api
Not necessarily, but the signature algorithm would have to change.

Block chain itself is based on hashes, which are already quantum hard. QC will not break SHA256. However addresses are based on ECC crypto, which would no longer be secure. These would have to be replaced by another scheme like supersingular isogeny ECC or lattice based crypto. Old BTC addresses would need to have their coins moved out of them to new addresses or those coins could be stolen by anyone with a sufficiently advanced QC.

There's a lot of post-quantum crypto research underway.

Interestingly this would permit the recovery of "lost" coins, bringing more BTC into circulation. Any coins that weren't moved -- meaning nobody cared about them or wallet keys had been lost -- would get recovered and returned to circulation.

What I consider much more intriguing is how the NSA is apparently hoovering monstrous amounts of Internet data and storing it on disks. Much of that data is encrypted, but once QC becomes available they will be able to go back and decrypt almost all of today's Internet traffic. That will be... interesting. It would be kind of like a crypto "jubilee" in which all yesterday's secrets become known.

somid3
Ok and this transition will take YEARS, while a hack will only take one night.
api
QCs won't appear overnight. We will see someone demonstrate a small-scale QC that is too small to usefully break real world crypto. As soon as that happens, there will be a rush to migrate everything to post-quantum crypto. Anyone not doing this with their coins as soon as they can is a fool.

It's possible that bigger QCs will appear in the "black" world before they are publicly known, but in that case they're not likely to be used to steal bitcoin since doing so would indirectly reveal their existence. If too many BTC wallets get silently snarfed, people will suspect a break. Anyone with such a QC would be better off sitting and passively monitoring for as long as they can.

somid3
My general rationale is that if DOA failed because of a single hack, then although its expensive today to run an experiment on a quantum device, it's still worth the millions that can be harvested. So accessibility is not a barrier. Likewise, if this event were to take place, it would be a winner take all scenario. All hacks will occur overnight in one go, since there is no reason to leave money on the table.

So if the potential is there, and the science is there, I feel all blockchain technologies are at risk.

somid3
By 2025 I will show this thread to all my friends who lost their savings as a time stamped proof that I saw the acopalypse that was headed their way.
lawrenceyan
I mean, sure cryptocurrencies would be total foobar, but so would basically every financial institution and bank in the world too. And this is assuming that neither preemptively secure there systems for post-quantum.
bbcbasic
With Bitcoin you need to transition and get consensus. A bank can just upgrade their systems.
samlewis
If you don't reuse Bitcoin addresses, then your Bitcoin will be safe. Bitcoin public keys aren't revealed until they're used to sign a transaction. An address is the SHA256 hash of the public key and SHA256 is quantum safe.

That said, the method of transaction signing would need to be reworked to be quantum safe. But not all Bitcoin would be able to be disappeared overnight.