Post-Quantum Cryptography (PQC) is the field of cryptography that deals with cryptographic primitives and algorithms that are secure against an attack by a large-scale quantum computer.
There are cryptographic algorithms based on mathematical problems that cannot be easily solved by a quantum computer. These algorithms fall into five categories
- Hash-based
- Code-based
- Lattice-based
- Multivariate
- Supersingular isogeny-based
A major issue for post-quantum cryptography is the lack of standardisation, making a widespread deployment of PQC difficult and impractical.
The National Institute of Standards and Technology in the USA (NIST) has made a call for proposals for crypto-systems that are secure against quantum computers.