Trust Degradation as State Transition: Policy-Defined Narrowing of Permitted Actions

Mechanism

Trust is represented within the governance framework as one or more scalar quantities, or vectors of scalars, attached to the governed object as part of its substrate state. Each scalar corresponds to a dimension of trust the policy chooses to track separately — for example, freshness of attestation, freshness of policy acknowledgement, behavioral conformance, or the integrity of the object's lineage. The policy binding attached to the object specifies, for each dimension, a decay function that maps elapsed time, or count of intervening events, to a reduction in the scalar.

The decay function is bounded. It is not permitted to produce a negative trust value, and it is not permitted to produce a trust value above the policy's defined ceiling. The function is monotonically non-increasing in its time-or-event argument absent an affirmative replenishment event, and it is required to be Lipschitz-continuous so that small changes in elapsed time produce only small changes in trust. The combination of boundedness, monotonicity, and continuity ensures that trust evolves predictably and that its state at any moment can be reproduced by any party that holds the inputs.

The trust scalars are inputs to the eligibility evaluation that gates each operation class. The policy binding establishes, for each operation class, a minimum trust profile required for the class to remain permitted. As trust decays past these thresholds the policy narrows the set of permitted classes, removing the highest-risk classes first and retaining lower-risk classes for longer. The narrowing is a deterministic function of the trust scalars and the policy thresholds; it is not the result of a separate decision but is implied by the values themselves.

Replenishment of trust requires presentation, to the substrate that maintains the object, of evidence drawn from a class enumerated by the policy. Acceptable evidence may include a fresh attestation signed by an authority entitled to attest, a successful completion of a policy-defined challenge, an external proof such as a recent audit record, or a combination thereof. The evidence is verified against the policy and, on successful verification, produces a mutation descriptor that updates the trust scalars to a value defined by the policy. The mutation descriptor is committed to the lineage in the ordinary way, so that the replenishment is permanently recorded along with the evidence that justified it.

Because the decay is deterministic and the replenishment is gated on evidence, the construction enforces a structural property: an object whose conditions are no longer being affirmatively maintained will, over a bounded interval, lose access to operation classes whose risk profile depends on current conditions. The system does not require an active policing entity to revoke privileges; the privileges narrow themselves through the absence of input, and they restore themselves only through the presence of fresh input.

Operating Parameters

The decay function is parameterized by a half-life, a floor, and a ceiling. The half-life specifies the elapsed time at which an unreplenished trust scalar reaches half its ceiling value; typical configurations place the half-life between minutes and weeks depending on the operation taxonomy the policy governs. The floor specifies the minimum value the scalar may reach in the absence of replenishment; configurations may set the floor to zero, so that unreplenished trust eventually disqualifies all permitted classes, or to a positive value, so that a residual capability is preserved.

The ceiling specifies the maximum value the scalar may attain on replenishment, and may be itself a function of the evidence presented. Configurations may grant a higher ceiling for evidence drawn from a stronger class — for example, a hardware-rooted attestation versus a software-rooted attestation — so that the strength of the evidence is reflected in the duration of the trust it produces.

The narrowing schedule is parameterized by a sequence of thresholds, each associated with a class or set of classes that becomes unavailable when the corresponding threshold is crossed. The schedule may be monotonic, so that classes are removed in a fixed order as trust decays, or may be class-specific, with each class associated with its own threshold independent of the others. The schedule is part of the policy binding and is itself committed to the lineage.

Evidence freshness is itself bounded. Evidence presented for replenishment carries a timestamp, or a verifiable freshness proof, beyond which the evidence is treated as stale and rejected. The freshness bound on evidence is typically tighter than the half-life of the trust it replenishes, so that an attacker who captures a stale attestation cannot use it to replenish trust on demand.

Lineage anomalies — events such as a failed verification of a prior mutation descriptor, an out-of-order transition, or a transition signed by a key that has since been revoked — are recorded as inputs to the decay function in addition to elapsed time. A lineage anomaly may produce an immediate decrement of trust by a policy-defined amount, may shorten the effective half-life, or may zero the trust scalar outright. The treatment of anomalies is itself a policy parameter and is committed to the lineage.

Failure modes are explicit. An object whose trust scalars cannot be evaluated — because an input is missing, a lineage record fails verification, or the policy binding is unrecoverable — is treated as having minimum trust, not as having maximum trust or unknown trust. The construction is biased toward narrowing in the face of uncertainty, and this bias is structural rather than configurable.

Alternative Embodiments

In a first alternative embodiment trust is represented as a single scalar with a single decay function, and the narrowing schedule consists of a single threshold below which all operation classes are denied. This embodiment is suitable for objects whose risk profile does not vary across operation classes.

In a second alternative embodiment trust is represented as a vector of scalars, each tracking an independent dimension, with each operation class governed by a vector-valued threshold that all components must exceed. This embodiment supports independent decay of independent conditions and is suitable when, for example, attestation freshness and behavioral conformance are tracked separately.

In a third alternative embodiment the decay function is implemented as a step function rather than as a continuous decay, with trust holding constant for a defined interval and then dropping to a lower value at the interval's end. This embodiment is suitable when the inputs that justify trust are themselves discrete events rather than continuous conditions.

In a fourth alternative embodiment replenishment is partial rather than total: presentation of evidence increases the trust scalar by a policy-defined increment toward the ceiling rather than restoring the scalar to the ceiling outright. This embodiment supports configurations in which trust is built up over multiple successful evidences and is not granted in full on the basis of any single evidence.

In a fifth alternative embodiment the decay function depends not only on elapsed time but on observed event counts — for example, the number of operations performed against the object, the number of failed eligibility checks, or the number of lineage anomalies. This embodiment supports policies in which trust degrades in response to use as well as in response to time.

In a sixth alternative embodiment the trust scalar and its decay function are themselves rotated through ordinary lineage transitions, so that a policy update may change the half-life or the narrowing schedule. The transition itself is committed to the lineage, and the new function takes effect from the moment of transition.

Composition

Trust degradation composes with the eligibility indicator: the trust scalars are inputs to the indicator's evaluation function, and changes in trust necessarily produce corresponding changes in the indicator. A consumer that reads the indicator therefore observes the current effect of the trust state without reading the trust state directly.

Trust degradation composes with the lineage chain: each replenishment event, each policy-driven transition of the decay function, and each anomaly-driven decrement is itself a lineage event, so that the complete history of the object's trust evolution is preserved. A reviewer reading the lineage may reconstruct, at any past moment, what trust the object held and what classes were therefore permitted.

Trust degradation composes with verified authority: the keys entitled to sign mutation descriptors that replenish trust are the keys named in the policy binding, and rotations of those keys are themselves lineage events. An object whose trust depends on attestations from a particular authority will, on rotation of that authority's keys, continue to evaluate trust correctly because the authority's identity is anchored to the lineage rather than to a specific key.

Trust degradation composes with downstream consumers in that a consumer that observes a low or zero trust scalar may itself reduce its own trust in the object's outputs, propagating the narrowing through the system. The construction does not prescribe this propagation but admits it as a natural consequence of the trust state being publicly readable.

Distinction Over Prior Art

Conventional credential systems treat authorization as a binary state — granted or revoked — and rely on expiration timestamps to bound the duration of grants. Expiration is binary and discontinuous: the credential is valid until its expiry and then ceases to be valid. The construction differs in that the state is continuous between full trust and no trust, and the narrowing of permitted classes is graduated rather than total.

Conventional reputation systems track a continuous trust score but typically treat it as advisory: the score is provided to a relying party that decides for itself how to interpret it. The construction differs in that the trust scalars are inputs to a deterministic eligibility computation whose output is enforced by the substrate, so that a low trust scalar produces an actual narrowing of capability rather than a recommendation.

Conventional time-based one-time password and rolling credential systems require periodic refresh but do not couple the absence of refresh to a graduated reduction in capability — the credential is either valid or not. The construction differs in that the absence of refresh produces a continuous decay along a defined curve, and the curve itself is a policy parameter committed to the lineage.

Conventional revocation mechanisms — certificate revocation lists, online revocation status protocols — require an active determination by an authority to remove a credential from circulation. The construction differs in that no active determination is required: in the absence of replenishment, trust narrows of its own accord, and the authority is required only to act when restoration is desired.

Disclosure Scope

The disclosure encompasses any construction in which trust held by a governed object is represented as a quantity that decays along a bounded curve in the absence of affirmative renewal, where the decay produces a deterministic narrowing of permitted action classes through reference to policy-defined thresholds, and where replenishment requires presentation of evidence drawn from a class enumerated by the policy and is itself recorded as a state transition in the object's lineage.

The disclosure is not limited to any particular form of decay function, choice of half-life, granularity of the action taxonomy, or class of admissible evidence. Implementations using exponential decay, linear decay, step functions, event-count decay, or compositions thereof fall within the scope so long as the function is bounded, monotonic in the absence of replenishment, and committed to the lineage. Evidence classes including signed attestations, challenge-response proofs, audit records, hardware-rooted measurements, and combinations thereof are within scope.

The disclosure extends to systems in which trust is tracked as a single scalar, as a vector of scalars, or as a structured record of independent dimensions, and to systems in which the narrowing schedule is monotonic, class-specific, or itself a function of additional state. The structural properties — bounded decay, evidence-gated replenishment, deterministic narrowing, and lineage commitment — are preserved across these configurations.