Some widely used public-key methods rely on mathematical problems that suitable quantum algorithms could solve efficiently on a large enough quantum computer. Post-quantum methods use different mathematical foundations for functions such as key establishment and digital signatures.
For example, a communication protocol can use a post-quantum key-establishment method without sending information through a quantum device. Protection still depends on the chosen method, correct implementation and the surrounding system. The label does not mean every possible security threat is removed.
ELI5
Post-quantum cryptography is preparing security designs for a world where an attacker might have a powerful quantum computer.
For example, an organization can study replacement methods and how its systems would transition without assuming that a particular quantum attack will arrive on a known date.
Does post-quantum mean quantum hardware is required?
No. These cryptographic methods are designed for conventional computers and networks.
Does it replace every security safeguard?
No. Software quality, access controls and other protections remain necessary alongside the cryptographic method.
