Quantum computers are nowhere near usable for breaking classical cryptography at the moment, though opinions on how soon it will come vary. As others have said, we have quantum resistant algorithms ready to go, so future encryption is fine.
The greater concern is that a lot of traffic and data encrypted using classical algorithms has been logged or stored in various mediums. An old encrypted drive, or communications stored by nation state actors (the NSA and such). These will be broken, and a lot of past secrets might come out from hiding.
An old encrypted drive
All of these use ciphers that are only affected by Grover’s algorithm. This basically halves the exponent on your key space (so instead of 2^128 keys you only have 2^64 keys), however this doesn’t necessarily mean that the algorithm is faster than a good parallel brute force on classical computers.
The more problematic algorithms are the ones affected by Shor’s algorithm, which are all algorithms in broad use today that involve some sort of agreeing on a shared secret.
Meh… we used to use much weaker encryption algorithms, and kept upgrading those algorithms. This will just be another phase of making stronger encryption algorithms. AES-256 is already quantum resistant, we just need to work on a quantum resistant asymmetric system. Pretty sure we can get it done before a quantum computer with enough qbits is invented.
This video by Veritasium was pretty insightful on the topic.
But I guess we’ll have to see about “store now, decrypt later”…
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New assymetric algos exist and the new standard is worked on right now IIRC (it might have been done already).
Not happening soon and when it does, we’ll have better algorithms that can’t be cracked by quantum computers.
There are already quite a few approaches to quantum safe encryption. We’ll just have to switch to different algorithms. It’s really nothing to worry about.