Security model
The v2.4.0-rc.1 layered verifier reports evidence integrity, signer authenticity, causal linkage, continuity, checkpoint and transparency proofs, witness observation, equivocation, anchor, finality, readback, and reconciliation as thirteen separate dimensions.
The enterprise retains action authority, credentials, signing-key custody, source access, and deployment controls. Optional reference layers are not claims of a production federation or mainnet service.
Layered result composition
Each conclusion is derived from the supplied artifact, explicit trust policy, and applicable deployment evidence.
- A passing signature or anchor changes only its own assurance dimension.
- Missing optional artifacts remain NOT_PROVIDED or INDETERMINATE; they never become success.
- Artifacts from different log, epoch, head, root, witness, or anchor contexts cannot be spliced into one passing report.
- Factual truth is always reported as NOT_DETERMINED_BY_PROTOCOL unless a separate external authority supplies evidence.
- Core verification makes no hidden network request; optional collection and readback are explicit.
- Neutral semantic binding and classification never authorize or prevent dispatch by themselves; active enforcement exists only in a correctly deployed enterprise-local guardrail.
Trust boundaries by layer
| Surface | Claim |
|---|---|
| Execution Receipt | Represents one domain-neutral lifecycle statement without defining or controlling the external action. |
| Enterprise-local Semantic Dispatch Guardrail | Internally derives K and F, enforces durable lineage-lifetime uniqueness, and gates one preconfigured adapter behind evidence-first single-use permit consumption. |
| Append-only local journal | Preserves record order and lifecycle links; external ordering and completeness are evaluated separately. |
| Ordered checkpoint | Binds an explicit stream, epoch, sequence, predecessor, range, and evidence root; continuity remains scope-relative. |
| Receipt Commitment | Binds an Execution Receipt hash to its declared-signer signature; source identity and factual truth remain policy-evaluated dimensions. |
| Receipt Bundle | Packages lifecycle-linked Execution Receipts and Receipt Commitments for offline verification. |
| Hosted artifact gateway | Stores closed, signed public artifacts for delivery and durability; database append-only controls are not Merkle transparency. |
| Transparency operator | Appends checkpoint entries and signs linked RFC 9162 tree heads; inclusion and consistency do not prove capture completeness. |
| Witness and monitor | Retains and compares exact-context signed heads under explicit authorization; operational independence is externally governed. |
| Neutral tree-head anchor | Timestamps selected signed tree-head hash material; anchor presence cannot upgrade integrity, finality, or factual truth. |
| Layered offline verifier | Cross-binds supplied histories and reports thirteen dimensions separately without hidden network access. |
| Local MCP and HTTP ingress | Accepts evidence submissions locally while external action authority stays with the enterprise. |
| Verified backup and restore | Semantically verifies a credential-free single-host snapshot and refuses to overwrite a restore target. |
| Deployment preflight | Exercises the external signer and verifies live evidence, outbox state, and a retained backup inside the evidence boundary. |
| Bounded OpenMetrics export | Projects fixed capacity, backlog, readiness, and reason-code series without scope, policy, evidence, or private-data labels. |
| Signed readiness bundle | Requires the exact clean source HEAD, records its Git tree, and binds both with a fresh preflight and redacted deployment-profile hash to the enterprise signer. |
| Independent review | Review binds target-environment controls, identity policy, and operational evidence. |
Verifier trust inputs
- Source identity and authentication policy.
- Purpose-specific signer authorization and status.
- KMS/HSM custody, rotation, revocation, and recovery.
- Independent cryptographic, identity-policy, and privacy review.
Operational deployment controls
- Authenticate the local ingress and protect signing keys.
- Route every effect-capable credential path through the enterprise-local guardrail when guarded-dispatch assurance is required.
- Pin the reviewed semantic normalizer, approval verifier, preconfigured adapter, authoritative readback connector, and durable atomic store.
- Require lifetime uniqueness for
(enterpriseScopeHash, K, F), monotonic fencing, and one outbound dispatch per callback or downstream idempotency. - Keep the external action system outside hosted ChoiceProof.
- Define retention, backup, recovery, and access policy.
- Collect the bounded OpenMetrics snapshot and test staleness, paging, acknowledgement, and escalation.
- Create and independently verify the signed readiness bundle for the reviewed clean source commit and Git tree.
- Operate transparency retention, signed-head exchange, witness authorization, quorum independence, and recovery ceremonies.
- Apply a reviewed tree-head anchor cadence, RPC provider, and finality policy when the optional network layer is used.
- Run privacy, tamper, conflict, restart, and recovery tests.
Semantic dispatch assurance boundary
The guardrail derives K and F internally. Any historical fingerprint in the same scope and key lineage resolves to its stored operation for the lifetime of that lineage; consequently F1 → F2 → F1 cannot create a new permit or guarded callback.
Pre-dispatch evidence must commit before the store atomically consumes the fenced permit. The permitted winner begins its one guarded callback only after that transition commits. Every retry or recovery path at or after consumption is readback-only, and no state can become dispatchable again after callback timeout, cancellation, failure, or crash.
Under the certified deployment assumptions, one semantic binding revision can cause at most one guarded adapter callback. That assurance depends on complete credential-path mediation, stable normalization of all material fields, durable atomic compare-and-set, and fencing. Extending the callback bound to downstream external effects additionally requires an adapter that emits at most one outbound dispatch or uses downstream idempotency. It is not an absolute statement about bypass paths or external effects.
Hosted ChoiceProof, public verification, transparency, witnesses, anchors, and contracts remain neutral: they do not dispatch an external action or custody adapter credentials.
Security references
Review SECURITY.md, docs/THREAT_MODEL.md, docs/SECURITY_REVIEW_SUMMARY.md, docs/KNOWN_LIMITATIONS.md, and docs/PRODUCT_ARCHITECTURE.md in the repository.
Factual truth, legal status, regulatory approval, observation coverage, and external-action authority remain separate trust and policy dimensions.