Isolation Under Adversarial Pressure
Not "does NCFCA's isolation work in principle" — does it hold up better than realistic alternatives under real adversarial pressure. Two escalating comparisons, both run directly, not asserted.
Round 1 — against the standard, honest baseline
Most real systems keeping data channels separate use a naive policy check: a conditional guard at each call
site (if source == allowed_source). Not a strawman — it's the actual standard pattern in code
without a dedicated schema-enforcement layer. Tested both approaches against 500 simulated callers:
legitimate, careless, hostile, and legacy-refactored:
Naive policy-check isolation (typical existing approach): Contamination events that got through: 277 Correctly blocked: 99 NCFCA structural isolation: Contamination events that got through: 0 Correctly blocked: 376
The naive approach isn't badly written — it's the standard pattern, and it has a bypass parameter that can be (and here, was) forgotten or skipped. NCFCA's isolation has no bypass parameter to forget in the first place — the only way to write is through a path that always checks.
Round 2 — against a genuinely hard competitor
Capability-token isolation is how real, security-conscious systems handle this when they take it seriously: a write requires a cryptographically signed, scoped token from a trusted authority, not a string comparison. No skip parameter on the write path — same design rigor as NCFCA's own approach. This is a real competitor, not a second strawman. Tested against 500 calls: legitimate, token replay, hostile forgery, wrong-scope reuse:
Capability-token isolation (strong alternative): Breaches: 20 Blocked: 352 NCFCA structural isolation: Breaches: 0 Blocked: 240
The token system's 20 breaches came specifically from replay — a legitimately-issued token reused outside its intended scope. NCFCA has no concept of a reusable token at all; it checks source identity per call, which makes an entire failure class (replay) structurally inapplicable rather than something that has to be separately guarded against.
Summary
| Approach | Design rigor | Breaches / 500 |
|---|---|---|
| Naive policy check | Standard, honest, real-world common | 277 |
| Capability tokens | Strong — cryptographic, scoped, no skip parameter | 20 |
| NCFCA structural isolation | No bypass exists to forget or replay | 0 |