Chapter 26
Post-quantum cryptography
A large quantum computer would break RSA and elliptic-curve cryptography, so key exchange is already moving to ML-KEM, and signatures and certificates come next.
Topic
Post-quantum cryptography
A large enough quantum computer would break the public-key algorithms in use today, such as RSA and elliptic-curve cryptography, while symmetric encryption such as AES is only weakened, not broken. Data recorded now could be decrypted later.
New post-quantum algorithms are standardised, and hybrid key exchange already protects many TLS connections. This hub explains what changes, what to do now and how to test it.
Understand it: handbook chapters
Plain words first, then the real mechanism, what it looks like at work and why it matters.
Chapter 4
Key exchange and hybrid encryption
Two parties can agree a shared secret over an open network without ever sending it, then derive fast symmetric keys from it to protect the actual data.
Chapter 6
Digital signatures
A digital signature is a value only the private-key holder can compute for a message, and anyone with the public key can check that it matches that exact, unchanged message.
Do it: how-to guides
Step-by-step, with real commands and a way to check it worked.
How to test post-quantum hybrid TLS
You will know whether your servers and network negotiate the X25519MLKEM768 hybrid key exchange, and how to read, force and troubleshoot it with OpenSSL 3.5.
How to configure TLS securely (versions, ciphers, HSTS)
You will have a web server that offers only TLS 1.2 and 1.3 with forward-secret ciphers, staples OCSP only where it still applies, sends HSTS safely, and passes testing.
The big picture: crash course
Short lessons of about nine minutes each, with check questions.
Look it up: glossary terms
Every term in plain words, linked to its full entry.