Chapter 11 — Cryptography and trust services: assets and context
Lesson map
Lesson 11 published. Map, example, EX031.
flowchart TD
N0["Learning outcomes"]
N1["11.1 Building the asset list"]
N2["11.2 Rating importance"]
N3["11.3 Recording context"]
N4["Synthesis"]
N0 --> N1 --> N2 --> N3 --> N4
N4 --> EX["Worked example"]
EX --> Q["Exercise EX031"]
Logical drawing
flowchart LR
N0["Learning outcomes"]
N1["11.1 Building the asset list"]
N2["11.2 Rating importance"]
N3["11.3 Recording context"]
N4["Synthesis"]
N0 --> N1 --> N2 --> N3 --> N4 --> Q["EX031"]
[Learning outcomes]
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v
[11.1 Building the asset list]
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v
[11.2 Rating importance]
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v
[11.3 Recording context]
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v
[Synthesis]
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v
[Worked example] --> [Exercise EX031]
Learning outcomes
You will (1) inventory cryptographic assets across council services; (2) rate each asset's importance; (3) record context such as legal retention and suppliers.
11.1 Building the asset list
Using her Chapter 4 model, Rosa populates the inventory: 58 certificates, 14 keys in the key service, the internal CA signing key, the document-signing key and two webhook secrets. She gathers data from scanning authorised hosts, exports from the key service and interviews with service owners. Each asset gets an owner and a service link. She discovers a certificate for an old events website that was retired years ago but still renewed automatically, wasting effort and widening the attack surface. It is removed after the owner confirms.
11.2 Rating importance
Rosa rates assets by the harm their compromise or loss would cause. The document-signing key is rated critical because forged decisions could have legal effect. The internal CA key is critical because it could mint any internal identity. Public website certificates are high: compromise would allow impersonation, but they are short-lived and replaceable. Webhook secrets are high because forged payment notices could issue permits without payment. Ratings determine which controls, such as hardware protection and dual control, each asset receives.
11.3 Recording context
Some context changes requirements. Signed decisions must remain verifiable for at least ten years under the council's records policy, so the signing process needs timestamps and archived validation data. The payment webhook secret is shared with a supplier under a contract that requires rotation on request. Certain staff certificates are issued to contractors whose access ends with their contracts. Rosa records such context in the inventory, because a key's handling depends not only on its algorithm but on legal, contractual and organisational facts.
Worked example
Rosa inventories 58 certificates and other keys, removes a stale events certificate, rates the signing and CA keys critical and records a ten-year verification requirement.
Synthetic case. Counts and policies are invented.
Errors and limits
Ratings are judgements and should be reviewed. Inventories built once and never updated soon mislead.
Exercises
- EX031 — Stale certificate. What wasteful asset did Rosa discover? Rubric: 3 = certificate for a retired events website still auto-renewing;; 2 = stale cert;; 1 = vague;; 0 = none.
- EX032 — Critical assets. Which two assets were rated critical and why? Rubric: 3 = document-signing key (forged decisions) and internal CA key (mint any identity);; 2 = one;; 1 = vague;; 0 = none.
- EX033 — Ten-year context. What does the ten-year requirement imply for signing? Rubric: 3 = need timestamps and archived validation data for long-term verification;; 2 = timestamps;; 1 = vague;; 0 = none.
Synthesis
An inventory rated by harm and enriched with legal and contractual context tells each asset what protection it deserves.
Continue studying — chapter 11 of 30
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