Chapter 4 — Our running example: SecureShop

To keep this concrete, we'll secure the same system throughout the guide. Every Part adds a layer.

The system

                      +-------------------------------------------+
   customers  ------> |  shop.securesh.op        (web + API)       |
                      |    - browse products                       |
                      |    - log in / register                      |
                      |    - place orders, save card details        |
                      +---------------+---------------------------+
                                      |
                      +---------------v---------------------------+
                      |  orders-api    (internal service)          |
                      +---------------+---------------------------+
                                      |
                      +---------------v---------------------------+
                      |  PostgreSQL: users, orders, payment tokens |
                      +--------------------------------------------+

   staff -----> admin.securesh.op  (admin panel, SSH to the servers)

What we have to protect

Asset	Property that matters	Why
Customer passwords	Confidentiality	Reused elsewhere; a breach harms people directly
Payment tokens	Confidentiality + Integrity	Money, and PCI-DSS obligations
Order data	Confidentiality (per-customer)	Alice must not read Bob's orders
The price field	Integrity	A customer changing the price is fraud
The site itself	Availability	Downtime is lost revenue
Admin access	All three	Full compromise if lost

How each Part contributes

Part	Adds to SecureShop
2 — Encoding	Understanding why the session token being Base64 protects nothing
3 — Hashing	Storing passwords so a breach doesn't hand over accounts
4 — Symmetric	Encrypting payment tokens at rest, correctly
5 — Asymmetric	Signing API requests; the keys behind TLS
6 — Post-quantum	Making sure today's traffic isn't readable in 2035
7 — TLS	HTTPS that actually resists interception; internal mTLS
8 — SSH	Staff access to servers without passwords
9 — Network	Segmenting the database away from the internet
10 — Web	Fixing injection, broken access control, session flaws
11 — Operations	Detecting the breach you didn't prevent
12 — Projects	Building all of it for real

Practice (10 min, no code)

Before you learn any of the answers, write your instinct in notes.md:

How would you store the passwords?
Where would you store the key that encrypts payment tokens?
How would you stop a customer viewing another customer's order?
What stops someone changing the price in the checkout request?

Keep your answers. In Chapter 52 you'll compare them against what you've learned. Most people get at least two badly wrong, and seeing that is the point.

End of Part 1 — Milestone check

I can name the CIA triad and give a real failure for each
I can explain what a trust boundary is and what happens there
I can state the encoding / encryption / hashing difference from memory
I know the difference between authentication and authorization
I have written a threat model for one system I know
My lab is built and Juice Shop runs