Biological Continuity as Handoff Verification

Mechanism

A biological identity thread is a continuous time series of observations sufficient to characterize the bearer as a single coherent biological subject across the observation window. A handoff is any event at which the thread crosses a discontinuity: a session boundary, a device boundary, or a boundary between authorities responsible for the immediate vicinity of the bearer. The mechanism does not treat the handoff as a trust-creating event in itself; it treats the handoff as an event whose admissibility is determined by the coherence of the biological signal observed during and around the transition.

Coverage is the property that the biological signal is observable to at least one authority at every instant of the transition. Where coverage holds, the receiving authority can verify that the thread it begins observing is the same thread the prior authority was observing, by comparing overlapping windows of signal. The comparison is a coherence test, not a credential check: it asks whether the temporal evolution of the signal on either side of the transition is consistent with a single physiological subject in motion across the boundary.

A gap is an interval during which no participating authority observes the thread. Gaps are unavoidable in many operational realities: a bearer steps out of camera coverage, a device is set down and picked up by another, a vehicle passes through a tunnel between roadside authorities. The mechanism does not forbid gaps; it characterizes them. Each gap is recorded with its start and end times, the last-observed signal state, and the first-observed signal state on resumption. The record is the substrate on which downstream policy operates.

Rate-limiting is the response to uncovered transitions. When the receiving authority resumes observation after a gap, it does not immediately admit the thread at its prior authority level. Instead, the thread enters a probationary regime in which the rate at which it can issue authority-bearing actions is constrained. The probation persists until sufficient post-gap signal has accumulated to bring the coherence test back across its admission threshold. The rate-limit floor is policy-controlled and may differ by action class.

Coherence across the transition is evaluated against features of the biological signal that are robust across observation modalities and that are not under voluntary control on the timescale of a handoff. The mechanism is agnostic to specific feature families; it requires only that the chosen features admit a stable comparison and a calibrated threshold. The comparison produces a coherence score and a confidence interval, both of which are entered into the handoff record.

The handoff is a recorded event, not a silent state change. Every transition, covered or uncovered, generates a handoff record bound to the identity thread, the participating authorities, and the policy regime in force. The record is the auditable artifact through which later inquiry can reconstruct exactly what was observed, what was inferred, and what authority was admitted across the transition.

Operating Parameters

The coverage-overlap parameter specifies the minimum interval during which both the departing and the receiving authority must observe the thread for the transition to be admitted as covered. Below this overlap, the transition is treated as uncovered regardless of whether both authorities reported observation.

The maximum admissible gap parameter establishes the longest interval of non-observation that the mechanism will treat as a recoverable gap. Beyond this threshold, the post-gap thread is treated as a new thread requiring full re-establishment, not as a resumption of the prior thread.

The coherence-admission threshold sets the minimum coherence score required for the post-gap thread to be admitted as the same identity as the pre-gap thread. The threshold is class-dependent, with high-authority threads requiring higher coherence than low-authority threads.

The rate-limit schedule specifies the action-rate ceiling as a function of post-gap observation duration. Immediately after a gap, the ceiling is at its floor; the ceiling rises monotonically as observation accumulates and crosses checkpoints corresponding to coherence-threshold confirmations.

The authority-handoff timeout governs cross-authority transitions specifically. It bounds the interval within which the receiving authority must complete its initial coherence test or surrender the thread to a fallback policy.

The signal-staleness parameter governs how recently the pre-gap signal must have been observed for it to participate in the coherence test on the receiving side. Stale signal is excluded to prevent replay of long-past observations across long gaps.

Alternative Embodiments

In a single-device embodiment, the handoff is between sessions on a device the bearer is continuously holding. The biological signal is supplied by sensors on the device, and the coherence test runs locally with no cross-authority coordination. This embodiment addresses the specific failure of session-renewal flows in which the device cannot distinguish between continued possession and sudden loss of possession.

In a cross-device embodiment, the handoff is between two devices in proximity to the bearer. Both devices observe the bearer during the overlap window; the receiving device's sensors initiate observation while the departing device's sensors are still active. The coherence test is conducted across the overlap and the bearer's authority is migrated to the receiving device only when the test admits.

In a cross-authority embodiment, the handoff is between two authorities responsible for distinct spatial or operational domains. Examples include the transfer of a vehicle between roadside authorities, the transfer of a patient between care teams, and the transfer of a controlled physical object between custodial agents. Coverage in this embodiment may be supplied by ambient infrastructure to which both authorities subscribe.

In a degraded-coverage embodiment, the gap exceeds the threshold for direct coherence comparison but ancillary signals, such as kinematic continuity or environmental witnesses, are available. The mechanism admits these signals as supplementary evidence under explicit policy, with the resulting admission marked as ancillary-supported rather than coherence-confirmed.

In a multi-bearer embodiment, several threads cross the same transition simultaneously. The coherence test is conducted independently per thread, and the rate-limit regime is applied per thread, preventing one bearer's coverage gap from displacing another bearer's full-authority resumption.

Composition

A handoff record comprises: the identity-thread reference; the departing-authority identifier and its terminal observation timestamp; the receiving-authority identifier and its initial observation timestamp; the overlap interval if any; the gap interval if any; the coherence score and its confidence interval; the policy regime under which the handoff was evaluated; and the rate-limit schedule applied on the receiving side. The record carries an audit pointer to the underlying signal segments, redacted as policy requires but addressable for inquiry.

The pre-gap and post-gap signal segments are themselves stored or referenced as composed artifacts comprising a sequence of observations, a quality envelope, and a provenance attestation from the observing authority. The envelope characterizes signal-to-noise, sampling regularity, and modality across the segment, so that downstream coherence comparisons are conducted on quality-comparable inputs.

The handoff record participates in the broader identity-thread ledger. Each thread accumulates a sequence of handoff records over its operational lifetime, and the sequence is itself an audit object: a thread that has crossed many uncovered transitions in rapid succession is a distinct evidentiary picture from one that has crossed few transitions, all covered, over the same interval.

Prior-Art Posture

Session-token handoff in conventional infrastructures relies on the transfer of a bearer credential. The receiving party admits the credential without independent verification of the underlying subject. The mechanism described here replaces the credential-bearer assumption with a coherence test against an observed biological signal, and is therefore not vulnerable to credential interception or replay across the transition.

Federated re-authentication requires the bearer to reassert identity to each new authority, typically through possession of a secret or a hardware token. This admits a replay surface across the re-authentication step and imposes friction at every transition. The present mechanism admits transitions through observation continuity rather than secret presentation, eliminating the replay surface and the friction simultaneously where coverage holds.

Continuous-authentication systems exist that monitor a bearer for ongoing authenticity. They typically operate within a single device and a single session. The present mechanism extends the continuity discipline across session, device, and authority boundaries, and treats the transition itself as an observable rather than as an interruption of observation.

Step-up authentication mechanisms, in which higher-risk actions trigger a re-prompt for credentials, address a related concern but operate at the granularity of the action rather than at the granularity of the transition. They cannot distinguish between a continuous bearer issuing a high-risk action and a successor bearer who has assumed the session and is issuing the same action. The present mechanism resolves this distinction at the transition itself, before any subsequent action is admitted under the post-transition authority.

Sensor-fusion identity systems combine multiple modalities at a single observation point. They establish identity at the instant of observation but do not, on their own, prescribe how identity is to be carried across an unobserved interval. The present mechanism uses fused observation as input to the coherence test but adds the discipline of explicit gap accounting and rate-limited resumption that fusion alone does not provide.

Custody-chain protocols in physical-asset domains record transfers between custodians but rely on attestation rather than independent observation. The present mechanism subsumes attestation but does not require it: where coherence is observed directly, attestation is corroborative rather than dispositive.

Disclosure Scope

The disclosure encompasses: the identity-thread continuity model and its observational substrate; the handoff-event taxonomy across session, device, and authority boundaries; the coverage, gap, and overlap definitions and their parameterizations; the coherence test as an admission criterion across transitions; the rate-limit regime applied to uncovered transitions and its schedule of relaxation; the handoff-record composition and its participation in audit; and the alternative embodiments enumerated above. The disclosure expressly contemplates method, system, and computer-readable-medium formulations, dependent claims directed to specific coherence-feature families, and dependent claims directed to specific rate-limit schedules and to ancillary-signal admission rules under degraded coverage.