Today's Plan (3 Hours)

Where Does This Week Fit?

• Weeks 4–11: we learned the protections (memory, crypto, obfuscation, whitebox…)
• This week (12): but do these protections really work? How are they tested?
• Week 13: security requirements and the compliance matrix

Today: independent evaluation + penetration test planning.

Learning Outcome

This week is about LO.6 / LO.7 (testing/verification, standards).

By the end, you will be able to:

• Explain the steps of independent evaluation
• Write a penetration test plan
• Rate a finding (attack potential, CVSS)

⚠️ Ethical and Legal Framework (From the Start)

A penetration test cannot be done without written permission and a contract with an explicitly defined scope.

• Unauthorized testing is a crime, whatever the intent.
• In this course, testing is done only on your own project.
• All data is synthetic; there is no real personal data.

Why This Section?

This week terms such as "evaluation," "certification," "penetration test" will come up.

Let's first define all of them one by one so the topic doesn't stay abstract.

What Is a Security Evaluation?

• Security evaluation: an independent party testing a product's security claims.
• Saying "I am secure" is not enough; evidence and testing are required.

What Is Certification?

• Certification: an authorized party documenting that a product/organisation complies with a given standard.
• If the evaluation succeeds, a certificate is issued.

Who Is the Laboratory (Evaluator)?

• Evaluation laboratory: the independent, accredited organisation that tests the product.
• It is not the organisation that develops the product (for impartiality).
• It has access to all source code and documentation.

What Is a Standard?

• Standard: a common set of rules defining what should be done and how.
• Examples: ISO/IEC 27001, Common Criteria, FIPS 140-3, PCI, OWASP MASVS.
• Each measures something different (more on this shortly).

What Is a Vulnerability?

• Vulnerability: a weak point in a system that can be abused (e.g., an unbounded buffer).
• Vulnerability + abuse = a security incident.

What Is a Finding?

• Finding: a problem or improvement point identified during evaluation.
• Every finding needs: evidence, severity, a recommendation.

White-Box vs. Black-Box Testing

• White-box testing: the tester has access to source code + documentation.
• Black-box testing: the tester accesses the system only from the outside (like a user).
• The evaluator usually works white-box (sees everything).

What Is SAST?

• SAST (Static Application Security Testing): a tool that analyses source without running it.
• Finds dangerous patterns and possible memory errors.
• Fast and broad; but produces false positives.

(We saw this in week 4 as "static analysis.")

What Is DAST?

• DAST (Dynamic Application Security Testing): tests the program while running it.
• Catches memory-access errors, undefined behaviour (e.g., with sanitizers).

(ASan/UBSan in week 4.)

What Is Fuzzing?

• Fuzzing: feeding a program unexpected/random inputs to look for crashes/corruption.
• Finds inputs a human would never think of.

(The libFuzzer/AFL concept in week 4.)

What Is a Penetration Test (Pentest)?

• Penetration test: attempting to break into a system from an attacker's point of view, with permission and in a planned way.
• Combines the methods above; the last and most expensive step.

What Is a TOE?

• TOE (Target of Evaluation): exactly what is being evaluated?
• A Common Criteria term.
• Identified uniquely: version + binary + source + hash value.

What Is CVSS?

• CVSS (Common Vulnerability Scoring System): expresses a vulnerability's impact as a standard score (0–10).
• Higher score = more severe impact.
• Used for prioritisation.

What Is Attack Potential?

• Attack potential: how difficult it is to carry out an attack.
• Scored with factors such as time, expertise, and equipment.
• Low potential (an easy attack) = a serious finding.

Attack Potential — Five Factors

Impact Analysis and Delta Assessment

• Security impact analysis: a report documenting the security impact of a change.
• Delta assessment: re-evaluating only the changed part.

We'll see these in detail in section 5.

Now We're Ready

The terms we know:

evaluation · certification · laboratory · standard · vulnerability · finding · white/black box · SAST · DAST · fuzzing · penetration test · TOE · CVSS · attack potential · impact analysis/delta

Now: why independent evaluation?

Independent Evaluation — Diagram

"My Code Is Secure" Is Not Enough

• A developer can be blind to their own code.
• Conflict of interest: you want to say "my product is secure."
• That's why third-party verification is required.

What Does Trust Rest On?

• Not on claims, but on evidence and testing.
• An independent laboratory: impartial, accredited, expert.
• Result: a certificate or a finding list.

The Evaluator's Two Assumptions

1. White-box: it has access to all source code and documents.
2. Platform is untrusted: the environment the product runs on is exposed to the attacker.

The Consequence of These Assumptions

A protection merely existing is not enough.

The evaluator asks: how easily is it bypassed?

• Not a single protection,
• but the time it takes to bypass protections together.

In Good Design the Attacker Is Forced

• A single protection → bypassed in a single step.
• Layered protection → the attacker must chain the layers.

This is the evaluation counterpart of the "layered defence" idea from weeks 9 and 11.

Standards Map — Diagram

Why Are There So Many Standards?

Each standard secures a different thing:

• the organisation, the product, or the crypto module?
• which domain (IoT, payments, mobile)?

Knowing which one your project is closest to tells you which tests to prioritise.

ISO/IEC 27001

• What: certifies the organisation (its processes).
• Not the product, but the organisation's information security management.
• Asks for control evidence instead of testing.

Common Criteria (ISO/IEC 15408)

• What: certifies the product.
• Source review + vulnerability analysis + penetration test + attack potential.
• Depth increases with EAL (week 13).

FIPS 140-3

• What: the cryptographic module.
• Algorithm validation, self-tests.
• Covers only the module, not the whole application (week 13).

ETSI EN 303 645

• What: baseline IoT security requirements.
• A light, broad-coverage baseline.
• E.g., "store sensitive parameters securely".

EMVCo / PCI

• What: payment products.
• Functional conformance + laboratory penetration test + attack potential.
• Strict and detailed.

OWASP MASVS + MASTG

• MASVS: mobile application security requirements.
• MASTG: the test guide for testing them.
• The most applicable guide for your project.

Organisation or Product? (Often Confused)

• ISO/IEC 27001: organisation.
• Common Criteria: product.

An organisation can hold ISO 27001 while its product has not been evaluated; the reverse is also true.

Section 1 — Quick Check

1. Why isn't it enough for the developer to say "it's secure"?
2. The evaluator's two assumptions?
3. What do ISO 27001 and Common Criteria certify separately?

Section 1 — Answers

1. The developer is a party with interest (conflict of interest), is blind to its own mistakes, and has no evidence in hand. An independent evaluator verifies with evidence.
2. (1) The attacker fully knows the system (Kerckhoffs), (2) the attacker is skilled and resourced. Assume the worst case.
3. ISO 27001 certifies the organisation/process (information security management), Common Criteria certifies the product (TOE) at a given assurance level.

The Evaluation Process — Diagram

Three Phases

The process is split into three phases:

• Preparation (1–4)
• Evaluation (5–8)
• Result and continuity (9–13)

Now let's take them one by one.

Preparation Steps — Diagram

Step 1 · Target of Evaluation (TOE)

• What is to be evaluated is defined uniquely.
• A version number is not enough: binary + source + hash value/label.
• Out-of-scope components are written down.
• In your project: S0, S1 (version identity, week 1).

TOE Identity — Diagram

Step 1 · Why Unique?

• The report is only valid for the binary examined.
• "v1.2" can point to two different builds.
• The hash value pins down exactly which file it is.

Step 2 · Delivery of Documents

• Source code, API documentation, security guide.
• Debug and release builds.
• Delivered over a secure channel.
• In your project: your repo + your guide.

Step 3 · Requirement Template

• The standard's numbered requirements.
• For each: the text, test coverage, the developer's compliance rationale + document reference.
• Status: met / transferred / not met.
• In your project: S17 compliance matrix (week 13).

Step 4 · Workshop

• Which control meets which requirement?
• How will gaps be closed?
• A document-update plan comes out of it.

Step 5 · Source Code Review

• All source is reviewed in a white-box context.
• Dangerous patterns, incorrect crypto, leak points.
• In your project: week 4 CERT, static analysis.

Step 5 · Where Does the Evaluator Look?

• Is crypto usage correct? Where does the key come from/go to?
• Input validation, memory (bounds, overflow, UAF).
• Secret leakage in logs/errors.
• Control-bypass paths.

Step 6 · Vulnerability Analysis

• Assets and the key hierarchy are extracted.
• For every asset: "where, in what state, is it exposed?"
• Output: finding list + penetration test plan.
• In your project: S4, S5, S16.

Step 7 · Penetration Test

• Every item in the plan is carried out with the eight-field template.
• Every finding is rated with attack potential.
• Output: test result tables.
• In your project: S16.

Penetration Test Plan — Diagram

Step 8 · Functional Conformance

• The product's standard functions (e.g., payment flows) are tested with the scheme's test suite.
• Output: execution report.
• In your project: unit tests.

Step 9 · Findings and Fixes

• For every finding, the laboratory produces a recommendation, the developer produces an action.
• Some findings close as "not a security issue, a good-practice suggestion".
• In your project: week 7 finding–action list.

Finding Cycle — Diagram

Step 10 · Security Impact Analysis

• When fixes produce a new version:
  • change category (new feature / improvement / bug fix)
  • affected files
  • security impact
• In your project: S13, change management.

Impact Analysis ↔ Delta — Diagram

Step 11 · Delta Assessment

• Only the changed part is re-evaluated.
• The laboratory asks for: marked-up documents, impact analysis, file list, the new TOE identity.

Step 12 · Trade-Off and Residual Risk

• The cost of every protection is measured.
• Decisions are justified.
• Residual risk is written explicitly.
• In your project: week 1 trade-off record.

Step 13 · Change Management

Baseline → request → classification → approval → development and testing → release → verification.

• In your project: S13.

Where Does the Guide Fit?

• The security guide that is the source of this course's "How it's done in the field" notes = the document delivered at step 2.
• Its primary reader: the laboratory.
• Every section opens with a requirement block ("requirement — status").
• The guide in your project is a scaled-down version of this.

Section 2 — Quick Check

1. The three phases, and roughly which steps?
2. Why is the TOE defined uniquely?
3. The relationship between impact analysis and delta assessment?

Section 2 — Answers

1. Preparation (TOE, scope, requirements, plan · 1–4), Evaluation (apply method, test, rate), Result (report, compliance, decision, ongoing delta maintenance).
2. To pin down precisely what is certified: version, build, hash, configuration. Otherwise a different version can appear "certified."
3. On a change, first the impact analysis (does it affect security?); if it does, not the whole product but only the delta (the changed part) is re-evaluated.

Evaluation Methods — Diagram

Purpose

Steps 5–6 of the process require using a set of methods in the right order.

Question: "How do I test my own product before I deliver it?"

The Right Order: Cheap to Expensive

1. Source code review (manual)
2. Static analysis (SAST)
3. Dynamic analysis (DAST) + sanitizer
4. Fuzzing
5. Penetration test

Cheap + broad → expensive + deep.

Why This Order?

• SAST is cheap, scans broadly; but produces false positives.
• Manual review is expensive; but sees context.
• Fuzzing requires running the program; finds what no one would think of.
• Penetration test is the most expensive; comes last.

Clear "easy" findings first with cheap methods → the penetration test can focus on real, combined problems.

Method 1 · Source Code Review

• Finds logic errors that automated tools miss.
• A human eye sees context and intent.

Code Review · Where to Look (1)

• Crypto: is the right algorithm/mode/padding used? Where does the key come from/go to/get erased? (weeks 3, 10, 11)

Code Review · Where to Look (2)

• Input/memory: bounds checking, integer overflow, format string, UAF (week 4 CERT).
• Leakage: sensitive data in logs, internal state in errors.
• Bypass: a control that can be bypassed with a single branch/return (week 9).

Method 2 · Static Analysis (SAST)

• Scans the source without running it.
• Memory errors, dangerous calls, patterns.
• Fast; but false positives must be handled.

Method 3 · Dynamic Analysis (DAST)

• Tests the program while running it.
• Sanitizers (ASan/UBSan) catch memory-access errors, undefined behaviour.

Method 4 · Fuzzing

• The program is fed unexpected inputs.
• Crash/corruption paths are found.
• Reveals cases a human would never think of.

Method 5 · Penetration Test

• Combines the methods above, tests exploitability from an attacker's viewpoint.
• The most expensive; comes last.
• We'll plan it in detail in section 5.

Critical Point: The Developer Goes First

• These tools must also be run by the developer, and the results (S16) presented.
• The big difference for the evaluator:
  • "no one has tested this" vs.
  • "these tools were run, these findings were closed".

This is the counterpart of week 4's secure build pipeline (SAST + sanitizer + fuzz in CI).

Each Standard Emphasises Different Tests

Whichever family your project is closest to, do the tests it expects first.

Common Criteria

• Source review + vulnerability analysis + penetration test.
• Attack potential rating.
• Depth increases with EAL.

FIPS 140-3

• Cryptographic module tests.
• Algorithm validation, self-tests.
• Covers only the module.

EMVCo / PCI

• Functional conformance + laboratory penetration test.
• Attack-potential scoring.
• Payment domain; strict.

OWASP MASVS / MASTG

• Mobile application: static + dynamic testing.
• The most applicable guide for your project.

Test Methodology Guides

Mature public guides exist for how to run a penetration test:

• OWASP WSTG (web)
• OWASP MASTG (mobile)
• PTES, NIST SP 800-115 (general process)

These are not an "attack recipe," they are methodology — they make the result repeatable/comparable.

Section 3 — Quick Check

1. Why do we order the methods cheap to expensive?
2. What is SAST's weakness?
3. Why does it matter that the developer tests first?

Section 3 — Answers

1. Cheap/automated methods (SAST/DAST) filter out easy findings early; expensive human effort is spent only on what remains → efficient.
2. SAST doesn't run the code → high false positives, cannot see runtime/configuration/business-logic flaws, doesn't know context.
3. It closes easy findings cheaply (goes clean to the evaluator), lowers cost/delay → evaluation can focus on deep problems.

Not "Yes/No" but "How Hard?"

A protection merely existing is not enough; how easily it is bypassed is measured.

Common Criteria and payment schemes do this with attack potential.

This is the formal counterpart of week 9's "measuring obfuscation" (potency/resilience) framework.

The Question: "What Did It Take to Break?"

A finding's severity is decided by the answer to this question.

We score it with five–six factors; the points are summed; the total maps to a resistance level.

Factor 1 · Elapsed Time

• How long did the attack take?
• Low score: a day. High score: months.

Factor 2 · Expertise

• What level of skill was required?
• Low: an ordinary user. High: a domain expert.

Factor 3 · Knowledge of the Target

• What needed to be known about the product?
• Low: publicly available information. High: internal/confidential documents.

Factor 4 · Window of Opportunity

• How much access/how many attempts were needed?
• Low: unlimited/remote. High: restricted physical access.

Factor 5 · Equipment

• Which tools were needed?
• Low: standard, free. High: specialised, expensive.

Interpretation: Low Total = Serious Finding

• High total → the attack is hard → the protection is good.
• Low total (ordinary user, one hour, free tool) → serious finding.

The logic is the same as week 9's four metrics.

Worked Example (Synthetic)

"A licence check in the release build depended on a branch that an ordinary-level user, with a free
disassembler, found in an hour and bypassed with a single-byte patch."

Example · Scoring

• Time: low · expertise: moderate · knowledge: public · equipment: free
• → low attack potential → serious finding

Recommendation: opaque boolean + random exit (week 9) + server-side check.

Attack Potential ↔ CVSS — Diagram

What Does CVSS Add?

• Attack potential: "how hard is it to break?"
• CVSS: "how big is this vulnerability's impact?"

The two complement each other.

CVSS · Likelihood vs. Impact

• One weighs likelihood (the attack's difficulty), the other impact (loss of confidentiality/integrity/availability).
• Both are usually given together in the report.
• Prioritisation is based on both.

Evaluation Is a Cycle

Not a "pass/fail" stamp, but an improvement cycle.

Four steps for every finding:

Four Steps

1. Finding: what the laboratory found (with evidence, repeatable).
2. Recommendation: the suggested direction of the fix.
3. Action: what the developer did (or why not).
4. Closure: some findings close as "not open, a good-practice suggestion".

This cycle → the source of the post-midterm finding–action list (week 7).

Why Do We Need These?

Fixes produce a new version.

Re-evaluating everything from scratch is expensive.

Two documents come into play (steps 10–11).

Security Impact Analysis

• Classifies changes: new feature / improvement / bug fix.
• Lists affected files.
• Writes the security impact of each change.
• The developer's output.

Delta Assessment

• Based on this document, re-evaluates only the changed part.
• Asks for: marked-up documents, change list, file list, new TOE identity.
• The laboratory's job.

⚠️ Do Not Confuse the Two

• Impact analysis: documents the change's impact (developer).
• Delta assessment: re-evaluates only the change (laboratory).

If the version identity/hash is inconsistent, delta cannot be done (the evaluated product becomes ambiguous).

Section 4 — Quick Check

1. The five factors of attack potential?
2. Why is a low attack potential a serious finding?
3. What do attack potential and CVSS each measure?
4. Whose job is impact analysis, whose is delta?

Section 4 — Answers

1. Elapsed time · expertise · knowledge of the target · opportunity (access) · equipment.
2. It means the exploit can be done with little time/skill/tools → many more attackers can do it → a broad, likely threat → high risk.
3. Attack potential measures the attack's difficulty/cost; CVSS measures the vulnerability's severity/impact. Different axes, used together.
4. Impact analysis is the developer's job (they initiate the assessment of the change's impact); delta assessment is the evaluator's job (they independently re-review it).

What Was a Penetration Test?

• An activity that combines the methods from an attacker's viewpoint, planned and permitted.
• "Planned" and "permitted" are not optional.

A plan contains at least four headings.

Heading 1 · Scope

• What will and won't be tested is written explicitly.
• Which binary/version, which components, which environment (test or production), which data (synthetic only).
• Out-of-scope items are also written down (third-party servers, real user data).

Heading 2 · Rules of Engagement (1)

• Written permission and an authorised signature.
• The test window (date/time).
• Permitted and forbidden methods (e.g., excluding those that cause service disruption).

Heading 2 · Rules of Engagement (2)

• Data rule: no real personal data; findings are confidential.
• Kill switch: if a critical impact is observed, the test stops, reported immediately.
• Communication and escalation points.

Heading 3 · Methodology

• Choose a recognised methodology and follow it:
  • mobile: OWASP MASTG/MASVS
  • web: OWASP WSTG
  • general: PTES, NIST SP 800-115
• Goal: the result is repeatable and comparable.

Heading 4 · Test Template

Every test is written with the same eight-field card.

This card is your project's S16 skeleton. Let's look at the fields now.

Test Card · Fields 1–4

1. Test ID: a unique number
2. Related requirement: which asset/requirement it tests (S17 link)
3. Purpose: what is being verified
4. Preconditions: environment, version, data

Test Card · Fields 5–8

5. Method/steps: in repeatable form
6. Expected result: what secure behaviour should be
7. Observed result: what happened (with evidence)
8. Decision: attack potential + pass/fail + recommendation

Worked Example · Test Card (1)

ID: T-05
Requirement: the sensitive record in the local database must be protected with AEAD (S17)
Purpose: is the record found in plaintext on disk?

Worked Example · Test Card (2)

Precondition: release build, a synthetic record inserted
Steps: run the application → add a record → scan the database file with strings
Expected: plaintext is not visible

Worked Example · Test Card (3)

Observed: no plaintext visible (only an encrypted blob) — evidence: output screenshot
Decision: pass · attack potential high (an easy attack failed)

The goal isn't to find a flaw, it's to learn to write a proper card.

Team Activity (In Class)

• Each team picks one asset from its own project.
• Fills in one test card for it.
• 15 minutes; then a few cards are shared.

The Report's Four Sections — Diagram

A Good Report = a Decidable Document

Not a list of "you failed."

The reader must be able to decide what to do.

Report Sections (1)

• Executive summary: overall status for the non-technical reader + the three most critical findings.
• Methodology and scope: what was tested, what wasn't, with which methodology.

Report Sections (2)

• Findings: each with evidence + attack potential + CVSS + recommendation.
• Finding–action table: the developer's response, closure.
• Residual risk: what wasn't closed/was transferred, with justification.

Critical-Reading Exercise

Read a short finding text together:

• Was the attack potential rated correctly?
• Is the recommendation actionable?
• Does the "met" row have evidence?

This is a rehearsal for reading the compliance matrix in week 13.

Section 5 — Quick Check

1. The plan's four headings?
2. Why does the "kill switch" exist?
3. Which field of the test card links to S17?

Section 5 — Answers

1. Scope · rules (RoE) · methodology · test cards (+ kill switch, reporting).
2. To limit real harm/data loss/disruption risk; at a defined threshold the test stops → safe and ethical execution.
3. The test card's result/requirement-met field → links as evidence to the S17 compliance matrix.

Project · S16 (Test Plan + Results) — 1

1. Write eight-field test cards for the two–three most critical assets/requirements (linked to S17).

Project · S16 — 2

2. Methodology: state which methodology (MASTG / WSTG / PTES / NIST SP 800-115) you're basing it on.

Project · S16 — 3

3. Results: run the tests and write the observed results.

At the final, a plan is not expected, a result is.

Project · S16 — 4, 5

4. Finding–action: pour your midterm feedback into a table.

5. Residual risk: write the risks you didn't close and why.

⚠️ Ethics (Again)

• Test only on your own project and systems you're authorised for.
• Unauthorised testing is a crime.
• All data is synthetic; no real secrets/personal data in the repo.

Question 1

Summarise the 13 steps in three phases.

Answer: Preparation (TOE, documents, requirement template, workshop) → Evaluation (code review, vulnerability, penetration, functional) → Result (finding, impact analysis, delta, residual risk, change management).

Question 2

The evaluator's two assumptions? What follows from them?

Answer: (1) white-box — full source/document access; (2) the platform is untrusted. Consequence: a protection existing is not enough, how easily it is bypassed is measured.

Question 3

Why do we order the methods cheap to expensive?

Answer: Cheap/broad methods (SAST) clear easy findings; the expensive/deep method (pentest) can then focus on real, combined problems. Time and cost efficiency.

Question 4

What do ISO 27001 and Common Criteria certify separately?

Answer: ISO 27001 certifies the organisation (process), Common Criteria the product. One does not require the other.

Question 5

The five factors of attack potential? Why is a low score serious?

Answer: time, expertise, knowledge of the target, window of opportunity, equipment. A low total = an easy attack = a serious finding.

Question 6

What do attack potential and CVSS each measure? Why together?

Answer: Attack potential measures likelihood (difficulty), CVSS measures impact (loss of C/I/A). Both are given together for prioritisation.

Question 7

The finding–recommendation–action cycle. How can a finding close as "not open"?

Answer: The laboratory produces a recommendation, the developer produces an action. Some findings close, with justification, as a good-practice suggestion, not a security vulnerability.

Question 8

The difference between impact analysis and delta assessment? Whose job is each?

Answer: Impact analysis documents the change's impact (developer); delta re-evaluates only the change (laboratory).

Question 9

The four headings of a penetration test plan?

Answer: scope, rules of engagement, methodology, test template. Each makes the result legitimate, repeatable, and safe.

Question 10

Why does a "kill switch" exist in the rules of engagement?

Answer: If a critical/unforeseen impact is observed, the test stops immediately and is reported; it limits harm and legal risk.

Question 11

Which field of the test card links to S17?

Answer: the "related requirement" field — every test is tied to a requirement/asset, tracked with the compliance matrix (S17).

Question 12

What does it mean that at the final S16 needs "results," not a "plan"?

Answer: Writing a test plan is not enough; you must run the tests and present the observed results and finding–action.

Summary: This Week in One Sentence

Security is not a claim, it is a quality independently tested and measured; a protection existing is not
enough, how much it withstands is measured in a planned, permitted, and repeatable way.

References

• Secure programming technical guide — the delivered document, impact/delta structure, requirement block
• OWASP MASVS / MASTG — mobile requirements + test guide
• OWASP WSTG — web test guide
• PTES, NIST SP 800-115 — penetration-test methodology
• Common Criteria (ISO/IEC 15408) + attack-potential guides
• CVSS

Case · Scenario

A synthetic mobile application: "NotKasa" (keeps encrypted notes locally).

• Encrypts notes with AES.
• Downloads the key from the server.
• Logging is off in the release build.

We'll evaluate this product start to finish.

Applying Step 1 · TOE

• TOE: NotKasa v1.0.0, notkasa-1.0.0.apk
• Hash (SHA-256): a1b2… (synthetic)
• Source: notkasa/ repository, tag v1.0.0
• Out of scope: server infrastructure

Steps 2–3 · Documents and Requirement Template

• Delivered: source, security guide, both debug and release APKs.
• Requirement template: MASVS items numbered; each with status + evidence reference.

Step 5 · Code Review Findings (Synthetic)

• B-01: the key is erased in an intermediate variable, but the tmp buffer is not erased (it stays in memory).
• B-02: the error message on a decode failure leaks internal detail.

Step 6 · Vulnerability Analysis

• Assets: note content (C/I), data key (C/I), server token.
• Question: where is each asset exposed?
• Output: a penetration test plan (below).

Step 7 · Penetration Test Card (Summary)

• T-01 plaintext on disk? → pass (encrypted)
• T-02 does the key stay in memory? → fail (B-01 confirmed)
• T-03 does the error message leak? → fail (B-02)

Step 7 · T-02 Rating

• Time: low · expertise: moderate · knowledge: public · equipment: free (memory dump)
• → moderate-low attack potential
• CVSS: medium (confidentiality impact)

Step 9 · Finding–Action

Steps 10–11 · Impact Analysis + Delta

• The fixes produced v1.0.1.
• Impact analysis: 2 files changed, both on the memory/error path; the crypto flow did not change.
• Delta: only these two files + the new TOE identity (notkasa-1.0.1.apk) were re-evaluated.

Step 12 · Residual Risk

• If the device is rooted, a memory dump is still possible.
• Mitigation: short-lived key + server-side risk check.
• Written explicitly.

Case · Takeaway

• The 13 steps aren't abstract; they're concrete in a small product.
• Evaluation is a cycle: find → fix → re-evaluate.
• Your project is a scaled-down version of this.

Card · Crypto Verification

• Purpose: are notes really encrypted with AEAD?
• Step: inspect the encrypted blob's header/tag; is a corrupted tag rejected?
• Expected: corrupted tag → decryption is rejected.

Card · Key Lifecycle

• Purpose: is the key erased once the job is done?
• Step: scan memory after the operation.
• Expected: key bytes are not found.

Card · Release/Debug Distinction

• Purpose: is logging really off in the release build?
• Step: search the release APK with strings for the log string.
• Expected: the log string is absent.

Card · Upgrade Safety

• Purpose: can an old signed version be restored?
• Step: try installing a lower version.
• Expected: the downgrade is rejected.

Rule When Writing Cards

• Every card must be repeatable (someone else must be able to follow the same steps).
• Every card is linked to a requirement (S17).
• The "Observed" field is filled with evidence.

Mistake · A Plan Without a Result

• At the final, S16 expects a result.
• "We will test this" is not enough; "we tested this, here's what came out" is.

Mistake · "Met" Without Evidence

• In the compliance matrix, "met" without evidence counts as not met by the evaluator.
• Every row needs an evidence reference.

Mistake · Version Inconsistency

• Guide v1.0, code v1.1 → the product being evaluated is ambiguous.
• The version identity + hash must be consistent.

Mistake · Residual Risk Left Empty

• No product's residual risk is ever zero.
• An empty "residual risk" = an incomplete analysis.

Mistake · Ignoring Midterm Feedback

• The finding–action cycle is part of the process.
• Midterm findings must be closed by the final.

Mistake · Real Data in the Repo

• Real secrets/personal data = a serious finding.
• Everything must be synthetic.

Appendix · Closing

These appendices gave you a concrete template for writing your own S16:

• an end-to-end case
• card examples
• mistakes to avoid

A good test plan carries trust from claim to evidence.