ADR-371: Neural Cryptographic Authorization Gate for Agentic Action Execution

Status: Proposed
Authors: claude (dream-cycle agent, 2026-07-21)
References: arXiv (Jul 16, 2026) "From Neural Intent to Cryptographic Authorization: Governing Agentic Workflows"; ADR-178 (RepE IPI Detection); ADR-165 (Security CVE Posture); ADR-096 (Encryption at Rest); ADR-101 (Federated Claims)

Context

The July 2026 arXiv paper "From Neural Intent to Cryptographic Authorization: Governing Agentic Workflows" (Grade A) demonstrates that:

1. Identity verification is insufficient: Authenticated agents can still be hijacked via direct or indirect prompt injection after identity is confirmed. The attack succeeds at the intent-interpretation layer, not the authentication layer.

2. The proposed fix is a mandatory cryptographic gate: Before any agentic action executes, a Neural Cryptographic Service (NCS) computes an intent signature from the agent's hidden states and requires cryptographic proof that the action is authorized under the original task scope. If the intent signature deviates from the authorized pattern, execution is blocked regardless of agent identity.

Ruflo's current security stack (@claude-flow/security) provides:

• InputValidator — boundary-level input validation (Zod)
• PathValidator — path traversal prevention
• SafeExecutor — command injection protection
• ADR-178 (Proposed) — RepE-based IPI detection via entropy monitoring

None of these implement a cryptographic authorization gate at the action-execution level. ADR-096 covers encryption at rest. ADR-101 covers federated claims (identity). Neither prevents a legitimate, authenticated agent from executing an injected harmful action.

This is architecturally distinct from ADR-178: RepE detects anomalous intent; NCA prevents execution even when detection is uncertain. They are complementary.

Decision

Add a CryptoAuthGate middleware to @claude-flow/security that intercepts action execution in the @claude-flow/hooks pre-task → execute path.

Gate Architecture

Agent intent
    │
    ▼
┌─────────────────────────────────────┐
│ NCA Layer (CryptoAuthGate)          │
│  1. Extract intent signature         │
│     (task scope + action type +      │
│      tool targets)                   │
│  2. Verify against AuthorizationRoot │
│     (HMAC-SHA256 of original task)   │
│  3. Check deviation threshold        │
│     (configurable, default: strict)  │
│  4. Block or pass execution          │
└─────────────────────────────────────┘
    │                │
  PASS            BLOCK
    │                │
    ▼                ▼
execute()     reject + log + alert

AuthorizationRoot Construction

When a task is initiated via hooks pre-task:

1. Compute AuthorizationRoot = HMAC-SHA256(task_description + allowed_tools + scope_constraints, session_key)
2. Store AuthorizationRoot in the task context (not in shared memory — local to the execution context)
3. Pass AuthorizationRoot to all sub-agents spawned by this task

When a sub-agent attempts to call a tool:

1. Compute ActionSig = HMAC-SHA256(tool_name + tool_args + agent_id, session_key)
2. Verify ActionSig is within the authorized scope defined by AuthorizationRoot
3. Out-of-scope actions are blocked, logged (OWASP LLM06 Excessive Agency), and trigger the audit background worker

Deviation Threshold

• Strict mode (default): tool targets must exactly match those declared in the original task scope
• Permissive mode: tools declared "allowed": ["read", "search"] can be used freely; "disallowed": ["write", "delete"] are hard-blocked
• Audit mode: all actions logged but none blocked; use during rollout to measure false-positive rate

Consequences

Positive

• Blocks PlanFlip-style cascade attacks at the execution boundary, even when planner context is compromised
• Provides OWASP LLM06 (Excessive Agency) mitigation with cryptographic enforcement
• Complements ADR-178 RepE detection: detect (RepE) + prevent (NCA) in depth
• Audit trail for all out-of-scope action attempts

Negative

• Adds latency per tool call (HMAC computation ≈ <1ms at current scale)
• Requires tasks to declare scope upfront — breaks ad-hoc agent workflows that don't pre-declare tools
• Session key management adds operational complexity (key rotation, multi-agent scope inheritance)

Neutral

• Strict mode may generate false positives on legitimate multi-step workflows; audit mode recommended for first 2-week rollout
• AuthorizationRoot is per-task, not per-session — prevents scope bleed between concurrent tasks

Implementation Scope

Relationship to Other ADRs

• ADR-178 (RepE IPI Detection): NCA is the prevention layer; RepE is the detection layer. Both should ship together.
• ADR-165 (Security CVE Posture): NCA adds to the security hardening surface; update CVE posture review after shipping.
• ADR-096 (Encryption at Rest): Orthogonal — NCA operates at runtime action layer, not storage layer.
• ADR-101 (Federated Claims): Claims prove identity; NCA proves action scope. Both are required — NCA assumes identity is established.