what is the purpose of post-quantum cryptography?
Post-quantum cryptography exists to keep today’s and tomorrow’s data secure even when powerful quantum computers arrive that can break many of the cryptographic systems we use now.
What is post-quantum cryptography?
Post-quantum cryptography (PQC) is a family of cryptographic algorithms designed to resist attacks from large-scale quantum computers, while still running on ordinary (classical) computers and networks. Unlike quantum cryptography, it does not require quantum hardware; it is “just” new math and new algorithms that aim to stay secure against both classical and quantum attacks.
Today’s widely used public-key schemes like RSA and elliptic-curve cryptography (ECC) rely on math problems (factoring large numbers, discrete logarithms, elliptic-curve discrete logs) that a sufficiently powerful quantum computer could solve efficiently using algorithms such as Shor’s algorithm. PQC instead uses different hard problems (for example lattice-based, code- based, multivariate, or hash-based constructions) for which no efficient quantum attack is known so far.
The core purpose of post-quantum cryptography
You can think of the purpose of PQC as having a few tightly related goals.
- Protect confidentiality long term
A quantum-capable attacker could eventually decrypt many of today’s intercepted encrypted sessions (the “harvest now, decrypt later” risk) once they get a big enough quantum computer. PQC aims to ensure that data encrypted now remains confidential even if it is recorded today and only attacked years or decades later.
- Preserve integrity and authenticity
Digital signatures underpin software updates, code signing, identities, and certificates on the web. Quantum computers could forge signatures from algorithms like RSA and ECDSA, enabling impersonation (for example faking a software vendor or website). PQC provides quantum-resistant signature schemes to keep verification of identity and data integrity trustworthy in a post- quantum world.
- Future-proof critical infrastructure and regulations
Governments, standards bodies, and large enterprises want cryptography that will still be safe for the lifetime of the data and systems they deploy today. PQC’s purpose is to provide standardized, interoperable building blocks so critical systems—financial networks, government communications, healthcare, industrial control, and the broader internet—can be upgraded before quantum attacks become practical.
- Enable a smooth migration from classical crypto
A key practical purpose is to allow organizations to transition gradually, using hybrid designs that combine classical and post-quantum algorithms while compatibility and performance are tested. This avoids a rushed “panic migration” later by encouraging planning, inventory of existing cryptography, and staged deployment now.
How this shows up in the real world (2020s–mid‑2020s context)
- Standards bodies such as NIST are publishing post-quantum encryption and signature standards (for example ML‑KEM/Kyber for key establishment and ML‑DSA/Dilithium and SLH‑DSA/SPHINCS+ for signatures).
- Security vendors, cloud providers, and browser/OS ecosystems are experimenting with or beginning to roll out PQC and hybrid protocols in TLS and certificate infrastructures.
- Organizations are being urged to inventory where they use RSA/ECC today, plan migrations, and prioritize long‑lived sensitive data (Government, healthcare, IP, critical infrastructure) that must remain secure many years into the future.
In short, the purpose of post-quantum cryptography is to make sure that the core promises of modern cryptography—confidentiality, integrity, and authenticity—continue to hold even in a world where quantum computers are powerful, widely available, and potentially in the hands of attackers.
TL;DR: Post-quantum cryptography creates new, quantum-resistant encryption and signature algorithms so that data, communications, and digital identities stay secure today and in the future, despite advances in quantum computing.