Mechanism
In the memory-native identity substrate, a device or agent expresses identity as a trust slope: the cumulatively validated sequence of Dynamic Agent Hashes (DAHs) or Dynamic Device Hashes (DDHs) produced by successive identity mutations, where each successor must be a valid descendant of the previously trusted state under policy-bounded checks. A device that participated in every step can retain the full slope, but a device with limited memory cannot. Sparse trust-slope recovery addresses this by letting a device retain only select dynamic identities, together with a compact checkpoint, and reconstruct the missing steps on demand from bounded proofs.
A checkpoint, as defined in the disclosure, is a retained and trusted identity state, either embedded in an agent or stored by a verifier, from which missing successors can be recomputed. The disclosure describes a device that retains only a few identity values, such as two non-adjacent slope points, plus a compact checkpoint summarizing all validated mutations up to that point. When continuity must be re-established, the device does not store the intervening steps: it recomputes them by deterministic forward replay from the stored checkpoint to the presented identity, using per-step materials supplied by a bounded slope proof.
This inverts the storage cost of continuity. Rather than holding every DAH or DDH on the slope, a memory-constrained device holds a checkpoint and a sparse set of identities, and recovers any required intermediate step only when a verification actually demands it.
Checkpoints and Sparse Retention
A checkpoint encapsulates the cumulative state of the trust slope at a specific epoch. Sparse retention holds only a few identity values. To rebuild continuity, the verifier loads the checkpoint, selects a bounded proof window, and iteratively reconstructs each missing identity step. Each reconstruction advances the slope and recomputes a successor until reaching the presented identity. The reconstruction is entirely local: each successor depends only on the prior dynamic identity and the disclosed per-step materials, so no persistent credentials, centralized ledgers, or synchronized registries are required.
The compact checkpoint summarizes all validated mutations up to its epoch. This is what allows a device holding only non-adjacent slope points to remain verifiable: the gap between retained points is bridged not by stored intermediate state but by a slope proof that carries just enough material to recompute that interval.
The Bounded Proof Window
A slope proof is a bounded disclosure containing the per-step materials sufficient for deterministic recomputation of the missing successors from a checkpoint or anchor, without revealing raw local state or static device secrets. For each step in the window, the proof supplies the unpredictability contributions used to form that successor: extractor tokens derived from stability-tuned local state vectors in the local-state embodiment, keyed derivations from a hardware anchor and a per-step volatile salt in the hardware-anchor embodiment, or both in hybrid embodiments. The proof window may also reference the most recent periodic anchor or a checkpoint to facilitate bounded replay.
The unrolled replay procedure evaluates a sequence of steps, obtaining per-step materials from the window and rebuilding successors in order. Where the local-state embodiment is used, a neighborhood constraint may be applied during replay to ensure bounded drift. Validation succeeds when the recomputed chain reaches the presented identity and opens against the referenced anchor or stored checkpoint.
Per-Step Commitments and Periodic Anchors
Per-step commitments provide tamper evidence during reconstruction. For each missing step the disclosure forms a per-entry commitment computed over the recomputed identity, the per-step token, and step metadata. These per-entry commitments are folded into periodic anchors at a fixed window size. The slope proof supplies the siblings necessary to open each per-entry commitment against the stored checkpoint and the relevant anchor, which allows compact proofs over long intervals. Validation succeeds when the recomputed chain matches the presentation and the opened commitments reconcile to the stored checkpoint or anchor.
An anchor, in the disclosure, is a periodic digest computed over lineage or commitments at selected intervals to support compact proofs and bounded validation across long histories. When periodic anchors are present, each reconstructed segment is opened against its corresponding anchor to ensure consistency. Once the final step of the bounded window is verified and the recomputed terminal value matches the presented identity, the verifier updates its local state, enabling subsequent validations or creation of a new checkpoint.
Checkpoint Requests
If the stored checkpoint is missing or outdated, the verifier issues a checkpoint request. A bounded checkpoint response provides either a fresh checkpoint or a short bridging proof sufficient to reach a trusted anchor. Because each successor depends only on the prior dynamic identity and the disclosed per-step materials, reconstruction continues to require only locally available materials and bounded disclosures, even when the verifier's stored state predates the available proof material.
This checkpoint-request path is what keeps a sparsely provisioned verifier from failing closed when its retained state is insufficient. Rather than rejecting the presentation outright, the verifier requests the minimal additional material needed to bridge to a trusted anchor and then completes the deterministic replay.
Neutrality to the Unpredictability Source
The sparse recovery mechanism is agnostic to the unpredictability source. Hardware-anchor embodiments provide keyed derivations tied to non-repeating salts. Local-state embodiments provide extractor tokens derived from stability-tuned local state vectors. Hybrid embodiments include both contributions in the same update step and require both to validate. Because the per-step materials carried in the slope proof match whichever source produced the original step, heterogeneous devices interoperate within a single recovery without weakening verifiability.
Policy determines checkpoint cadence, balancing storage overhead against replay cost. The disclosure states the tradeoff directly: frequent checkpoints reduce reconstruction complexity, while sparse checkpoints lower memory requirements at the cost of longer proofs. The disclosure does not fix a numeric cadence; it leaves the cadence to policy in the deploying environment.
Deployment in Memory-Constrained Environments
The disclosure situates sparse checkpointing in memory-constrained deployments such as IoT sensors, wearables, embedded controllers, and ultra-low-power endpoints. There, the system uses sparse checkpointing and forward-secure chaining to minimize storage: devices retain only selected identities and anchors and reconstruct intermediate steps as needed from compact proofs. Policy controls checkpoint cadence to balance memory load against replay cost, and acceptance remains strictly local and deterministic.
Sparse recovery composes with delayed validation, the mechanism for authenticating a presentation after latency or disconnection by replaying successors from a stored checkpoint or anchor using a slope proof. In intermittent and disconnected networks, a sender may include the per-step proof materials sufficient for deterministic replay from the recipient's last anchor, and the recipient reconstructs continuity upon reconnection without global synchronization. By combining sparse identity retention, embedded checkpoints, per-step bounded proofs, periodic anchors, and optional checkpoint requests, sparse trust-slope recovery enables verifiable reconstitution of identity continuity in memory-limited or intermittently connected environments using only locally available materials and bounded disclosures.
Disclosure Scope
Sparse trust-slope recovery using embedded checkpoints, comprising the retention by a memory-constrained device of only select dynamic identities such as two non-adjacent slope points together with a compact checkpoint, the bounded slope proof that supplies per-step unpredictability materials (extractor tokens over stability-tuned local state vectors, keyed derivations from a hardware anchor and per-step volatile salt, or both), the deterministic forward replay from the stored checkpoint to the presented identity, the per-entry commitments with commitment siblings that open against the checkpoint or a periodic anchor, the reconciliation of the recomputed chain to the stored checkpoint or anchor, the checkpoint request and bounded checkpoint response, and the policy-determined checkpoint cadence that balances storage overhead against replay cost, is disclosed in U.S. Application No. 19/388,580. This article describes that disclosed mechanism. The scope extends to embodiments that vary the unpredictability source, provided the device retains sparse identities and a checkpoint and reconstructs missing successors by deterministic, locally verifiable replay from bounded proofs and periodic anchors.
