# Is the proof-of-work algorithm “Quark” insecure?

I recently found out about Quark here: https://en.bitcoinwiki.org/wiki/Quark_Algorithm

Apparently it is a proof-of-work algorithm used by several cryptocurrencies and is based on a single-level hash function, which consists of 9 different levels of encryption by six cryptographic algorithms. It also says that Quark provides a "64-bit" protection against hackers.

Isn't 64-bits of protection considered rather insecure? I'm sure a hacker with sufficient computing power can break 64-bits of security given enough time and money. Or am I missing something?

• 32-bit collision resistance is surely inadequate, but to prove you've done $2^{64}$ work can sometimes exceed the capability of moderately sized high-end computers. – DannyNiu Feb 15 '20 at 7:01