[Blood of Tyrants]

It will render Bitcoin worthless.

[ClearCase_guy]

All my money is tied up in that Hawk Tuah coin system. I sure hope that holds on to its value!

[Pocketdoor]

I was just going to say, can’t QC be used to farm Bitcoin rendering it worth less.

[EnderWiggin1970]

Cryptocurrency folks have been aware of QC all along. We've had quantum-resistant test currencies at least since 2017. (See for example https://coinmarketcap.com/currencies/quantum-resistant-ledger/)

Even if a Q-day surprise appears, it will take a few hours to scramble and release a patch on bitcoin and other cryptos will quickly follow suit. And those of us not reusing change addresses won't be vulnerable anyway.

It is the fiat world that will be in trouble. The banking and credit card systems the world over will be vulnerable for weeks and unable to function. In fact, I've been wargaming a sudden Q-day scenario, and it seems likely to me that a Q-day event will be used by cryptocurrency advocates of the less savory sort to maliciously attack and wreak havoc on the banking system (zeroing some accounts, creating billions in others, and generally causing mayhem so that no fiat financial data can be trusted). The result will be to force the world to adopt cryptocurrency or be driven back to 18th century commerce.