- cross-posted to:
- cybersecurity@infosec.pub
- cross-posted to:
- cybersecurity@infosec.pub
AES-128 is safe against quantum computers. SHA-256 is safe against quantum computers. No symmetric key sizes have to change as part of the post-quantum transition. This is a near-consensus opinion amongst experts and standardization bodies and it needs to propagate to the rest of the IT community. The rest of this article backs up this claim both technically and with references to relevant authorities.
Original article: https://words.filippo.io/128-bits/
TL;DR: https://hackaday.com/2026/04/25/quantum-computers-are-not-a-threat-to-128-bit-symmetric-keys/
It’s secure because it’s symmetric. It can’t be cracked because there is no exposed secondary information.
Asymmetrical encryption relies on using information which is visible to the outside world to compute two keys using math that is very difficult to reverse. Quantum computers make that math MUCH easier.
But since symmetric encryption doesn’t do that. It’s safe.
this is good news if true
Good for security. What does this mean for quantum computing, though? Does this mean that it’s not as powerful as we thought it would have been?
Anybody who believed that quantum computing posed a risk to symmetric encryption was fundamentally misunderstanding how encryption works and what quantum computing might be good at one day.
Asymmetric cryptography is primarily used for the secure exchanging of symmetric keys: use a public/private key pair to exchange secure messages of what symmetric key to use for their session, and then both sides switch to the symmetric key for actual communication of a real payload.
A public/private key pair is two keys that have some interesting mathematical relationship, such that it is easy to confirm that someone possesses the right private key using the public key or to encrypt something that only the correct private key can decrypt. And that mathematical relationship, relating to the product of two very large prime numbers, is at the core of modern asymmetric cryptography.
Quantum computing may make number factorization much, much easier. So once a product of two large primes becomes possible to factor, the public/private key pairs might not be as secure anymore.
But none of this has anything to do with symmetric encryption, or hash functions. Quantum doesn’t move the needle on that particular math.
The real risk, though, is for an adversary to eavesdrop on an encrypted key exchange (which uses asymmetric cryptography) and then the message itself (which uses symmetric cryptography) and then be able to take the two steps of getting the secret symmetric key from the intercepted key exchange over a compromised asymmetric protocol, and being able to decrypt the symmetric portion of the communication too.
Interesting, thanks for the insight. IIRC, you can leverage data about the quantum state to detect eavesdropping though — can’t you? So in effect, if I do recall correctly, it’s introducing a nuanced problem while also introducing a generally applicable solution to it?
I think it means that there was probably some misunderstandings of how a qbit would do calculations or execute code.
Quantum computing has already been destroyed by AlphaFold.
I work in the computational chemistry field and I’d really love a working quantum computing solution to that kind of problems, but since the ML solutions came up most research in that direction stopped and it does not seem like there is any nearing solution in the world of quantum computing.
I’m not talking about qubits numbers or amount of errors themselves in the system but about the complete lack of algorithms that can handle the problem. Most of what I’ve seen is handling childlike problems that a single core CPU will do better and quicker anyway. It really does not feel like all the promises that have been done are anywhere near to coming true.
When I speak with people working in the field they’re like: sure in a few years if we can get better computers we’ll be able to handle a few hundred atoms at a time (all without any actual working methodology and assuming that will be developed), however we are more commonly talking about hundreds of thousands of atoms… There’s little hope on my part that anything useful will come out of there soon. However, I do really hope it does: quantum computing would be a huge revolution for chemistry if it works as advertised.
As expected the same dipshits pushing AI also lied about what quantum computing even is.
I’m imagining if I had said this even a month ago even though it’s what I’ve thought for years.
It’s most likely not the same people, as AI destroyed quantum computing. A person strongly invested into quantum computing would be crazy to push for AI.
Microsoft.
I’ll keep using AES 256 because why the heck not? The additional cost is a rounding error.
I mean, sure, don’t panic. But also, don’t hit the brakes. You might as well use the best encryption that’s readily available. Encrypted data does not have a short enough or predictable enough lifespan to justify using less than the state of the art.


