09_Protocols — Protocols — the primitives assembled

Level: 301 · working knowledge

Nothing you meet in a job is a primitive. It is a protocol: a sequence of them, with an order, a negotiation, and an identity claim. TLS, JWT, SSH, code signing, S/MIME — each one is the same handful of pieces arranged for a different threat model.

Reading a protocol is checkpoint 4, and the method is always the same three questions: who proves what to whom, in what order, and what happens if a step is skipped.

The pages

#	Page	The question it answers	Status
1	What a TLS handshake actually does	What actually happens between 'https://' and the page?	planned
2	JWT, and the alg:none hole	What does a signed token prove — and what was alg: none?	planned

Every page above is a plan until its row says written; see ROADMAP.md.

The through-line

The identity is the hard part. Key agreement is solved; knowing whose key you agreed with is what certificates, CAs and the whole trust apparatus exist for, and it is where protocols fail.