Concepts, explained in layers
Pick a topic and read it your way — start with a plain-English analogy, then climb through beginner, intermediate and advanced all the way to a deep technical dive. Diagrams throughout, a table of contents on every page.
Security
Kerberos authentication, explained from scratch
How tickets let you prove who you are once — and never send your password again.
The TLS / HTTPS handshake, explained
How two strangers agree on a shared secret in the open — and why the padlock means something.
Public-key cryptography, explained without the maths degree
Two keys are better than one — here is why the internet runs on asymmetric crypto.
Networking
How DNS works, from query to answer
The internet's phone book: how a name becomes an IP address, step by step.
Subnetting and CIDR, demystified
What the /24 really means, and how to split a network without fear.
How TCP works: handshakes, windows and reliable delivery
The protocol that turns a lossy, out-of-order network into a tidy, in-order byte stream.
DHCP explained: how a device gets its IP address
From zero to online in four broadcast packets — the protocol that hands out IP addresses automatically.
Linux
Linux file permissions, from rwx to capabilities
What ls -l is really telling you — and how the bits decide who can do what.
The Linux boot process, from power button to login
What actually happens between pressing power and seeing a login prompt.
Virtualisation
These pair well with the hands-on side of ShellQuest — try the troubleshooting puzzles or the calculators & tools.