Two kinds of encryption
The quantum question becomes clearer once you separate two jobs that encryption does.
Symmetric encryption uses one secret key to lock and unlock data. AES-256 is symmetric encryption, suited to a photo, document or vault on your device.
Public-key encryption helps two parties create a secure internet connection. It protects web browsing, messaging and online services by relying on maths difficult for ordinary computers.
Quantum computers could change the second job much more than the first. That is why “quantum will break encryption” is too broad a claim.
What quantum computers could change
A quantum computer is not simply a faster laptop. It may solve a few maths problems in a radically different way. One could undermine common public-key systems if a large, error-corrected machine becomes available.
That machine does not exist today. The timeline is uncertain, but companies and standards bodies are preparing now with post-quantum cryptography: methods designed to resist ordinary and quantum computers.
Why AES-256 encrypted files remain safe
AES-256 is in the better-positioned group. The best-known general quantum shortcut would reduce its effective strength from 256 bits to roughly 128 bits. A 128-bit key is still far too large to brute-force in practice.
A properly implemented AES-256 system remains an excellent choice for stored files. A weak passphrase, malware or an unlocked phone can still expose files without breaking AES.
Example: an AES-256 encrypted photo on your phone is not the same risk as an old internet connection recorded by an attacker. One uses a local secret key; the other may have used public-key methods while data travelled.
“Harvest now, decrypt later”
An attacker could record encrypted traffic now and keep it for years. If the public-key encryption used for that connection becomes breakable, the stored recording could be read.
This matters most for long-lived government, health, legal or business records. Services can reduce the risk with post-quantum methods. For personal files, use strong local encryption and protect the key.
What is changing online
Post-quantum standards exist, and browsers, operating systems, messaging services and websites are gradually adopting them. The transition will take time.
For most people, this happens through software and service updates. Installing updates is one practical way to benefit.
What this means for Sealby files
Sealby encrypts your files with AES-256 on your iPhone. Vault files do not depend on a public-key exchange with a Sealby server, so “harvest now, decrypt later” does not apply to their local encryption.
Use a strong PIN or passphrase, protect your device and install updates. AES-256 gives your files a large security margin as quantum technology develops.