alt Hacker NewsThe capabilities of quantum computing, in theory, are pretty well known. There's basically a few extra operations which can be done efficiently on it and so that can be built into the threat model, even if no-one's built a quantum computer yet.
(Of course, basically all encryption, especially asymmetric encryption, is predicated on there not being some as-yet-undiscovered exploitable structure to the mathematics on which it is built. Modern cryptography, AFAIK, tends to have some decent arguments for why this is not expected to be the case, but it's never completely proven top-to-bottom outside of fairly niche/trivial cases. It's always in principle possible that someone discovers an attack on these new algorithms, classical or quantum)
Supersingular Isogeny Key Exchange is one that was invented to be quantum-safe but turned out to be unsafe at any speed, so hybrid encryption is still a good idea. You use both a quantum-safe algorithm and a classical algorithm, encrypting your data twice and remaining secure if either one is broken.