Ordering Guarantees in a Single-Site Append-Only Attestation Log

An attestation asserts that a subject was present at a moment. The assertion is only as strong as the log's ability to place that moment relative to every other moment it holds. Ordering is therefore not an implementation detail of the log; it is the property the log exists to provide.

The problem is standard. Lamport [3] establishes that in a distributed system without a shared clock, a total order can be imposed by logical means, and that such an order is sufficient for most correctness arguments. Lamport is also explicit that the order so imposed is arbitrary between events with no causal relation, and that it can disagree with the order an outside observer perceives; that is the reason his paper goes on to introduce physical clocks. The distinction matters here more than it does in most applications, because an attestation is a claim about a moment and not only about a sequence. Haber and Stornetta [4] show how to bind a document to a position in a sequence such that the binding cannot be altered after the fact. Merkle [5] provides the tree construction on which NeuroCrypt's substrate, and the certificate-transparency logs described in RFC 6962 [2], both rest.

NeuroCrypt differs from these systems in one respect that matters: it operates at a single site, underground, with all 96 append terminals on a common power and timing infrastructure. Many of the difficulties that motivate distributed constructions do not arise here. This narrows the problem and, as §5 records, does not eliminate it.

For any two appends a and b accepted by the substrate, exactly one of a ≺ b or b ≺ a holds, and the relation is stable under all subsequent appends.

where n_x is the node written for append x, R_k is the root after the k-th append, and incl denotes that an inclusion proof for that node verifies against that root. An append precedes another exactly when some root commits to the first and not the second. Hashing is SHA3-256 as specified in FIPS 202 [1]; the inclusion and consistency proofs follow the construction described in RFC 6962 [2]. Signatures are hybrid: Ed25519 per RFC 8032 [6] composed with ML-DSA-65 per FIPS 204 [7], both required to verify.

The guarantee is enforced at write, not at read. There is no reconciliation step, no eventual consistency window, and no path by which a later append can reposition an earlier one.

The Ring's 8.8 km circumference is not chosen for capacity. It is chosen so that the confirmation path from any terminal to the root traverses a constant distance regardless of originating sector, removing sector position as a source of latency variance. The cost is that NeuroCrypt is larger than its compute requirement would suggest, which has been raised at every funding review and has not been changed.

This section is required by NC-GOV-0001 §4 and is not abridged for the Tier 0 release.

5.1 The guarantee is over appends accepted by the substrate. It says nothing about events in the world. An attestation that a subject was present is a claim about a terminal's observation, not a proof that the observation was correct.

5.2 Single-site operation is assumed throughout. The construction has not been analyzed for multi-site operation and should not be assumed to hold at the auxiliary sites.

5.3 Seventeen appends have required a tie-break. In each case two appends were presented within the same timing-resolution window, with no signal available to the substrate establishing which occurred first in the world. The substrate assigned an order by a documented procedure and flagged the assignment; per §2, that assignment is the log's order once written. The tie-break record exists because the assignment was undocumented by evidence, not because §2 leaves it undetermined. The procedure is ████ and is withheld in this extract.

5.4 Of those seventeen, three involved a pair in which one member had no identifiable originating terminal. These are treated in NC-TN-0203. The authors note, without drawing a conclusion, that the substrate ordered them successfully, which requires that both members of each pair were well formed.

5.5 No external review of this note has been sought. NeuroCrypt's position is that external review would require disclosure of the substrate's construction. This is a limitation of NeuroCrypt's posture, not of the result.