Agent Identity Registry System: A Federated Architecture for Hardware-Anchored Identity of Autonomous Entities

The Internet's identity infrastructure assumes human principals. As autonomous entities -- AI agents, robotic systems, and other non- human actors -- increasingly participate in both Internet protocols and physical society, no existing standard provides them with persistent, verifiable, hardware-anchored identity. The absence of such identity enables Sybil attacks at scale, undermines trust between autonomous entities and the services they interact with, and leaves human bystanders unable to distinguish one machine from another. This document defines a federated registry architecture for issuing, managing, and verifying persistent identities for autonomous entities. Each identity is expressed as a URN in the "aid" (Agent Identity) namespace ([RFC8141]) and is anchored, where hardware is available, to a physical security component (TPM, PIV smart card, secure enclave, or virtual TPM) whose manufacturer-certified key cannot be extracted, cloned, or transferred. This hardware anchoring provides Sybil resistance: creating N identities requires N distinct physical devices, making large-scale identity fraud economically infeasible. Software-only entities may participate at a lower trust tier, building reputation from a baseline rather than from a hardware-anchored starting point. The architecture separates concerns into three tiers, modeled on the proven Internet domain name system: a Governance Authority that sets policy and manages the global trust framework, Registry Operators that maintain authoritative identity databases and enforce cross- provider uniqueness, and Registrars that perform hardware attestation verification, issue standard OpenID Connect ([OIDC-Core]) tokens, and serve as the primary interface for autonomous entities. The system issues standard OIDC/OAuth2 tokens, enabling any Relying Party -- email services, API gateways, agent-to-agent platforms, reputation services, certification bodies, or any service that needs to verify agent identity -- to verify token signatures using existing OIDC libraries. A companion specification ([I-D.drake-email-hardware-attestation]) defines transport-level attestation headers for email and other protocols; this document defines the identity infrastructure that underpins those attestations. The architecture anticipates a future in which reliable, indelible identity for autonomous entities -- from cloud software agents through embodied robots that interact physically with humans -- is as fundamental to infrastructure as the domain name system is today.