SSH
SSH from first principles — a visual course covering architecture, the cryptography behind it, key exchange, authentication, keys and the agent, config and tunneling, security, and an end-to-end walkthrough.
Module 01 — Foundations & Architecture
Why SSH exists and how its three protocol layers stack on TCP to deliver confidentiality, integrity, and authentication.
Module 02 — Cryptography Behind SSH
The five cryptographic primitives SSH assembles into a secure channel — symmetric, asymmetric, hashing, MAC/AEAD, and signatures.
Module 03 — Key Exchange & Session Keys
How Diffie-Hellman and ECDH derive a shared secret over a watched network, then expand it into six directional session keys.
Module 04 — Authentication: Host and User
How SSH verifies the server via its host key (defeating MITM) and proves the user with passwords or public-key signatures.
Module 05 — Keys and the Agent
What's stored inside SSH keys, how to generate and protect them, and how ssh-agent signs without exposing the private key.
Module 06 — Config, Channels and Tunneling
Client/server configuration, the channel abstraction that multiplexes one connection, and how -L/-R/-D port forwarding works.
Module 07 — Security and Troubleshooting
Which attacks each SSH layer defends against, a hardening checklist, and a layer-by-layer method for debugging failures.
Module 08 — Complete Walkthrough
An end-to-end trace of a single ssh command — every packet and crypto operation from DNS to the remote shell prompt.