# Post-Quantum Cryptography **Post-Quantum Cryptography (PQC)** is classical (non-quantum) cryptography designed to remain secure against attacks by a large-scale quantum computer. It runs on today's hardware but uses mathematical problems believed to be hard even for [[Quantum Algorithms|quantum algorithms]] like Shor's. ## First principles - **The threat.** Shor's algorithm breaks RSA and elliptic-curve cryptography; Grover's weakens symmetric keys. So the assumptions underpinning today's public-key infrastructure expire once a cryptographically-relevant quantum computer exists. - **Harvest Now, Decrypt Later (HNDL).** Adversaries can capture encrypted traffic *today* and decrypt it later — so data with a long shelf-life is already at risk. - **The replacement primitives.** New hard problems: lattice-based (e.g. **Learning With Errors / LWE**, CRYSTALS-Kyber, Dilithium), hash-based, code-based, multivariate. NIST finalised the first standards in 2024. > [!warning] PQC's blind spot > PQC secures the *mathematical tunnel* — it does **not** verify the behavioural integrity of whoever holds the keys. A stolen-but-valid key still passes. This gap is exactly what [[Vyapti Resonance MOC|Vyapti Resonance]] targets with continuous behavioural trust. ## Related - [[Vyapti Resonance MOC]] — a behavioural-trust layer built to run alongside PQC - [[Quantum Algorithms]] · [[Why Quantum]] · [[Quantum Computing MOC]]