Module security 

P2-5: defense against malicious agents.

A4A agents can be impersonated, tampered with, or hostile. This module provides the building blocks to trust only what you should:

• Trust directory — TrustRegistry maps agent identities (their card url) to the verification key the directory attests, and keeps a revocation list (CRL). Cards are only trusted when they come from a known agent and their signature verifies against the registered key.
• Trust chain propagation — TrustRegistry::verify_chain walks a delegation path root → … → leaf, verifying every hop was signed by its parent, enforcing a maximum delegation depth and decaying the trust score with each hop (TrustConfig).
• Least privilege — SandboxConfig restricts an agent’s file/network access and payload size, checked via SandboxConfig::check.

Signature primitives are the HMAC-SHA256 card signatures shared with the client (sign_agent_card / verify_card_signature), so a registry and a client can agree on the same key material.

Structs

SandboxConfig

Least-privilege limits for a delegated agent (P2-5 sandbox).

TrustConfig

Delegation-depth and trust-decay policy for chain verification.

TrustRegistry

Trust directory: known agents, a revocation list (CRL), and chain policy.

TrustVerification

Result of a successful trust verification.

TrustedAgent

An agent the registry trusts, with the key used to verify its card.

Enums

AccessRequest

A resource access attempt to be checked against a SandboxConfig.

SecurityError

Error raised when a security check fails.

TrustRole

Role of an agent in a trust hierarchy. Drives the base trust score before hop decay is applied.