Concepts

Background on the cryptography CertMonitor inspects, useful whether you're new to TLS or brushing up before a post-quantum migration. These pages are vendor-neutral explainers; the Validators section shows how CertMonitor measures each thing in practice.

• How TLS & HTTPS Work: what the handshake does, where certificates fit, and the difference between key exchange and signatures (with a handshake diagram).
• Certificates & PKI: what's inside an X.509 certificate, the chain of trust, and how certificates are issued (with chain and issuance diagrams).
• Post-Quantum Cryptography: the quantum threat, harvest-now-decrypt-later, the NIST standards (ML-KEM / ML-DSA / SLH-DSA), hybrids, and the migration challenges.

New to all of this? Read them in order. Already fluent and here for the quantum-safe story? Jump straight to Post-Quantum Cryptography.