finding 49: adversarial evasion/tampering analysis on audit-log.md

New analytical lens (adversarial/offensive security) tested on gargoyle's
signal audit log spec. GPT-5 most exhaustive (25), Opus deepest individual
attack narratives (14), Sonnet most creative meta-attacks (11).

Adversarial lens is ~2.5x more productive than defensive lenses on
comparable docs. All three models converged on same root cause (trust model).

findings/2026-05-08-49-adversarial-evasion-tampering-audit-log.md

@@ -0,0 +1,122 @@
+# Finding 49: Adversarial Evasion and Tampering Path Analysis
+
+**Date:** 2026-05-08
+**Document:** gargoyle `audit-log.md` (170 lines) — Signal Audit Log specification
+**Lens:** Adversarial evasion and tampering paths (NEW)
+**Models:** GPT-5, Claude Opus 4.6, Claude Sonnet 4
+
+## Summary
+
+First experiment using an explicitly adversarial/offensive security lens — asking
+models to identify ways a malicious insider or compromised component could
+manipulate, evade, or undermine the audit system. The adversarial lens produced
+significantly MORE findings than defensive lenses (defense-in-depth, gap analysis)
+on comparable documents.
+
+## Results
+
+| Model | Time | Output tokens | Reasoning tokens | Findings | Critical | High | Medium |
+|---|---|---|---|---|---|---|---|
+| GPT-5 | ~97s | 9,508 | 5,376 | 25 | 5 | 12 | 8 |
+| Claude Opus 4.6 | ~105s | 5,477 | (internal) | 14 | 6 | 6 | 2 |
+| Claude Sonnet 4 | ~fast | 1,732 | (internal) | 11 | 4 | 4 | 3 |
+
+## Common Ground (all 3 identified)
+
+- Deliberate storage unavailability creates unaudited trading windows
+- Signal Risk write-only-on-rejection as silent bypass channel
+- signal_data snapshot falsification by trusted components
+- Correction entries as effective mutation mechanism
+- Retention policy weaponization (DE controls both retention and the log)
+- Signal ID reuse/collision for forward trace contamination
+- Multi-aggregator fan-out abuse for correlation dilution
+
+## GPT-5 Unique Findings
+
+- **Lossy aggregation via forced re-formation:** Disrupt atomic write → decision
+  "lost" → re-form with different signals. Original decision vanishes.
+- **Decision content vs executed order mismatch:** Audit records conservative
+  decision but OM receives larger order.
+- **Decision_id collision/merging:** Reuse IDs to co-mingle unrelated entries.
+- **Flood-and-hide with rejection storms:** Generate noise to overwhelm query views.
+- **Backdated corrections + timestamp smearing:** Writer-supplied timestamps
+  alter perceived event ordering.
+- **Decision_id ghost approvals:** Append late "approved" entries to justify
+  unauthorized executions.
+- **Correction recursion:** Chain corrections-of-corrections for irresolvable ambiguity.
+- **Forward-trace truncation via selective W1 gaps:** Block only rejections writes
+  while passing signals downstream.
+
+## Opus Unique Findings
+
+- **Signal Risk write failure as indistinguishable stealth bypass:** Attack looks
+  IDENTICAL to documented operational failures — built-in plausible deniability.
+- **Atomic write temporal gap exploitation:** Decision forwarded to PR BEFORE
+  audit write completes — trade executes without aggregation entries.
+- **Outcome mislabeling "accomplice" framing:** Audit system becomes an active
+  participant in concealment, not just failing to detect.
+- **Timing-based entry injection:** No "sealing" of decision_ids after atomic
+  write — other writers can inflate evidence retroactively.
+- **Portfolio Risk entry preemption:** Write false "approved" BEFORE PR evaluates,
+  creating irresolvable contradictions.
+- **Weaponized immutability via flooding:** Inject noise that can NEVER be cleaned
+  up — the system's strength becomes the attack vector.
+
+## Sonnet Unique Findings
+
+- **Schema evolution attack:** Introduce version field, write new entries with
+  same IDs + higher versions, modify queries to return "latest" — effectively
+  overwrite history through schema change. Uniquely creative meta-attack.
+- **Query semantic manipulation:** Modify query logic to filter out entries —
+  data exists but becomes invisible to operations.
+- **Decision ID fragmentation:** Split decisions so each fragment falls below
+  risk thresholds individually.
+
+## Key Insights
+
+### Adversarial analysis as a new task type
+
+Compared to defensive lenses, adversarial analysis requires:
+1. Attacker perspective ("how would I exploit this?")
+2. Plausible deniability reasoning ("how would this look legitimate?")
+3. Multi-step attack chain construction
+4. Impact from attacker goals, not system goals
+
+### Model strengths on adversarial tasks
+
+- **GPT-5:** Strongest at attack surface ENUMERATION — systematically covers
+  every exploitable gap. 25 findings covering essentially every section.
+- **Opus:** Strongest at attack PLAUSIBILITY — how attacks would be perceived,
+  what provides cover, second-order effects of design decisions.
+- **Sonnet:** Occasionally produces most creative META-ATTACKS that exploit
+  governance/authority rather than mechanisms. Fast and efficient.
+
+### Productivity of adversarial lens
+
+Finding #48 (defense-in-depth) on a comparable doc (209 lines):
+GPT-5: 10, Opus: 7, Sonnet: 6.
+
+Finding #49 (adversarial) on this doc (170 lines):
+GPT-5: 25, Opus: 14, Sonnet: 11.
+
+~2.5x more findings. A single design decision can be exploited in multiple ways
+from an attacker's perspective, while defense-in-depth identifies one gap per
+missing layer.
+
+### Root cause convergence
+
+All three models independently identified the same root cause: the audit log's
+trust model. The system records CLAIMS from trusted components, not independently
+observed facts. Any compromised writer can fabricate schema-valid entries
+indistinguishable from truth.
+
+## Practical Implication
+
+For architecture review rotation:
+- **GPT-5** for exhaustive attack surface (what COULD happen)
+- **Opus** for realistic threat modeling (how it WOULD play out)
+- **Sonnet** for creative lateral attacks (meta-level exploitation)
+
+The adversarial lens is the most productive new lens since cross-document
+consistency analysis. Generates more findings and produces directly actionable
+security improvements.