Part 0 — Start here
0.1 Who this guide is for
| You are… | Works for you? |
|---|---|
| A developer who has never studied security | Yes — this is the primary reader |
| A sysadmin/SRE who configures TLS and SSH by copying snippets | Yes — you'll finally know why |
| Someone moving into a security engineering role | Yes — this is the ground floor and several storeys up |
| A student preparing for Security+/CEH/OSCP foundations | Yes, as the "why" behind the syllabus |
| A cryptographer | No — this is applied, not theoretical. See Appendix E. |
Assumed: you can open a terminal, run commands, and read code loosely (Python and shell). You know what a file, a process, and a web request are.
Not assumed: any cryptography, any maths beyond arithmetic, any security vocabulary. Every term is defined on first use.