Chapter 1 — Computing and service architecture
Lesson map
Lesson 01 published. Map, example, EX001.
flowchart TD
N0["Learning outcomes"]
N1["1.1 The service map"]
N2["1.2 Where cryptography is used"]
N3["1.3 What quantum computers threaten"]
N4["1.5 Hands-on activity"]
N5["Synthesis"]
N0 --> N1 --> N2 --> N3 --> N4 --> N5
N5 --> EX["Worked example"]
EX --> Q["Exercise EX001"]
Logical drawing
flowchart LR
N0["Learning outcomes"]
N1["1.1 The service map"]
N2["1.2 Where cryptography is used"]
N3["1.3 What quantum computers threaten"]
N4["1.5 Hands-on activity"]
N5["Synthesis"]
N0 --> N1 --> N2 --> N3 --> N4 --> N5 --> Q["EX001"]
[Learning outcomes]
|
v
[1.1 The service map]
|
v
[1.2 Where cryptography is used]
|
v
[1.3 What quantum computers threaten]
|
v
[1.5 Hands-on activity]
|
v
[Synthesis]
|
v
[Worked example] --> [Exercise EX001]
Learning outcomes
You will (1) describe how a hotel's services fit together from device to data centre; (2) point to where encryption and signatures are used; (3) explain in plain terms what quantum computers threaten; and (4) tell which changes you can make yourself and which need a vendor.
1.1 The service map
At an HHG property, a front-desk PC runs the PMS client, which talks over the site VPN to the PMS server in the data centre. Card payments go from point-of-sale (POS) terminals to a payment processor. Door locks are programmed by a lock server through a hub. Guests use Wi-Fi to reach the internet and the guest portal. In the data centre, a load balancer fronts the booking API and portal; servers talk to the reservations database; a file-exchange server sends booking files to travel agencies. Drawing this map is the first job of any operator, because every later check refers to a box or arrow on it.
1.2 Where cryptography is used
Encryption protects data moving between boxes (TLS, VPNs, SSH) and stored data (disk and database encryption). Signatures prove who is who (certificates on servers, signed software updates, signed lock firmware). Each use has an owner and a change route: a setting you can change, a package you can upgrade, a vendor update, or a hardware replacement.
At HHG the guest portal's TLS can be changed by operations through configuration, while the signed lock firmware can only change with the lock vendor or new hardware. Write the change route next to every use you find, since it decides who must act and how long it will take.
1.3 What quantum computers threaten
A large, error-corrected quantum computer running Shor's algorithm (Shor, 1997) could break the public-key methods used today to agree keys and sign — RSA and elliptic curves. It would not meaningfully break AES-256 encryption or SHA-256 hashing. No such machine exists yet. Two risks follow: someone could record encrypted traffic now and decrypt it later ("harvest now, decrypt later"), and once such a machine exists someone could forge signatures. NIST has published replacement algorithms: ML-KEM (FIPS 203) for key agreement and ML-DSA (FIPS 204) and SLH-DSA (FIPS 205) for signatures.
1.4 Worked example
The operator lists cryptographic uses at the Harbour property: PMS client to server over site VPN (ECDH key exchange; change route: VPN appliance firmware, vendor); POS to payment processor (TLS; processor and POS vendor); lock firmware signed with RSA (lock vendor; hardware refresh); guest portal TLS at the load balancer (HHG operations; configuration). Only the last one is a change the operations team can make today.
The list makes the gap clear: most of the property's cryptography depends on vendors or hardware. That does not mean nothing can be done; it means the operator's other job is to record precise vendor questions for the VPN, POS and lock items, with model and firmware versions.
1.5 Hands-on activity
Draw the service map for one property from the description above. For each arrow write: protocol, owner, change route.
Include the less visible boxes: POS terminals, the lock hub and the guest Wi-Fi. For each arrow, name the protocol (TLS, IPsec, SSH or unknown), who owns each end, and whether a change is a setting, an upgrade, a vendor update or a hardware replacement. Mark any arrow you cannot fill in as unknown rather than guessing. Compare your map with a colleague's and resolve the differences; disagreements usually reveal a box one of you missed.
1.6 Common errors and limits
- Missing devices such as locks and POS terminals.
- Assuming every change is a setting.
- Saying quantum computers "break all encryption".
Each error makes the map misleading. Locks and POS terminals are easy to forget because nobody logs into them, yet the lock firmware is one of HHG's longest-lived trust points. Assuming every change is a setting makes plans look quicker than they are, because firmware and hardware routes take months or years. Saying quantum computers break all encryption is wrong: AES-256 and SHA-256 remain fine, and saying otherwise sends effort to the wrong places.
Exercises
- EX001 — Change routes. For five HHG cryptographic uses, give the change route. Rubric: 3 = five correct routes.
- EX002 — Plain explanation. Explain harvest-now-decrypt-later to a hotel manager in two sentences. Rubric: 3 = accurate and jargon-free.
- EX003 — Keep or replace. Which of RSA, AES-256, ECDH and SHA-256 must be replaced? Rubric: 3 = RSA and ECDH replaced; AES-256 and SHA-256 kept, with reasons.
Synthesis
A clear service map shows where cryptography is used, who owns it and how it can change. Quantum computers threaten public-key key agreement and signatures, not symmetric encryption.