Trust decay

Trust decay is the deliberate erosion of an agent's trust score over time or under behavioral drift, so that trust must be continuously re-earned by consistent action rather than granted once. Decay functions encode a security asymmetry: trust collapses instantly on hard evidence of compromise but recovers slowly, denying attackers the ability to wait out a brief penalty.

The asymmetry is the design. Fast collapse on evidence and slow recovery means an attacker who triggers a penalty cannot simply pause and resume, and a legitimate actor who triggers one is inconvenienced rather than locked out.

Decay also has to be bounded, or an idle but legitimate agent eventually decays into uselessness and someone raises its floor by hand, which quietly removes the property.

The asymmetry is the design rather than a side effect. Fast collapse on hard evidence and slow recovery means an attacker who trips a penalty cannot pause and resume on the original footing, while a legitimate actor who trips one is inconvenienced rather than locked out. A symmetric function gives both parties the same option and therefore helps the one with more patience.

Decay needs a floor, or an idle but legitimate agent eventually decays into uselessness and somebody raises its level by hand. That manual override is where the property usually dies, because an exception granted once tends to persist, so the floor belongs in the function rather than in an operator's discretion.

What the score is allowed to do on its own is the same question a trust coefficient raises, and decay sharpens it: a function that can drive an agent to zero can be driven there by an attacker generating anomalies deliberately. Reserving irreversible outcomes for hard signals, and letting decay govern graduated limits, keeps a defensive mechanism from becoming an attack surface.

Bounding the function is therefore a security decision rather than a usability concession.

Hard evidence of compromise should bypass the curve entirely and trigger a revocation cascade.