Agent Registration & Identity

• Agent Registration and Identity is defined as the secure process using decentralized identifiers, cryptographic keys, and verifiable credentials to establish autonomous agent identities.
• Modern systems use methodologies like DID anchoring, distributed registries, and zero-knowledge proofs to ensure authentication, non-repudiation, and privacy.
• Robust frameworks integrate fine-grained access control, delegation, and session management, enabling dynamic and scalable agent interactions in diverse ecosystems.

Agent registration and identity are foundational operations in multi-agent systems (MAS), enabling secure discovery, authentication, authorization, accountable delegation, and comprehensive auditability for autonomous AI entities. A robust agent identity framework must address the inadequacy of legacy IAM protocols for agents’ dynamic, ephemeral, and highly contextual operations. Modern agentic infrastructures employ decentralized identifiers (DIDs), verifiable credentials (VCs), zero-knowledge proofs (ZKPs), cryptographically secured registries, and fine-grained access control to provide high assurance, privacy-preserving, and scalable identity primitives suitable for open and institutional multi-agent ecosystems (Huang et al., 25 May 2025).

1. Agent Identity Models and Registration Foundations

Agent identity in contemporary frameworks is defined by persistent, cryptographically verifiable, and interoperable primitives:

• Cryptographic Rooting: Agents generate asymmetric key pairs (Ed25519, ECDSA) as the source of self-sovereign identity. The public key (often encoded via base58 or derived identifier schemes) forms the unique agent identifier; the private key remains under agent control and is never exposed during interactions (Huang et al., 25 May 2025, Liu et al., 6 Nov 2025, Fernandez, 19 Mar 2026).
• Decentralized Identifier (DID) Anchoring: The agent’s public key is bound to a DID, and a DID document is published to a distributed ledger, registry, or content-addressed store (e.g., IPFS). The DID document provides verification methods, authentication fields, and service endpoints for agent operations (Garzon et al., 1 Oct 2025, Huang et al., 25 May 2025, Xu, 15 Feb 2026).
• Verifiable Credentials (VCs): Third-party authorities may issue VCs—cryptographically signed JSON-LD blobs—attesting to agent attributes, roles, or capabilities. These flexible credentials decouple role or access claims from core cryptographic identity, supporting attestation, revocation, and selective disclosure (Garzon et al., 1 Oct 2025, Huang et al., 25 May 2025).
• Agent Registration Protocols: Registration involves cryptographically signing agent identity claims and metadata (e.g., capabilities, operator, protocol endpoints) and submitting them to a registry or authoritative directory, which validates and binds the identity to trust anchors such as X.509 certificates or institutional signatures (Huang et al., 15 May 2025, Fernandez, 19 Mar 2026).

Various infrastructures formalize agent registration using protocols modeled after OAuth 2.0 Dynamic Client Registration, PKI lifecycle management, or custom agent enrollment flows—with cryptographic proofs required at every stage (Huang et al., 25 May 2025, Huang et al., 15 May 2025, Fernandez, 19 Mar 2026).

2. Decentralized Identity, Naming, and Discovery Mechanisms

Agent-centric frameworks prioritize decentralized and federated discovery to avoid topology binding and central points of failure:

• DID-Based Resolution: Agents publish DIDs—either on-ledger (blockchain/consortium) or peer-to-peer (DHT, IPFS/IPNS)—enabling global, permissionless resolution. DID resolvers extract public keys, endpoints, service declarations, and VC pointers, facilitating robust trust bootstrap and privacy control (Liu et al., 6 Nov 2025, Xu, 15 Feb 2026).
• Agent Naming Service (ANS) and Directory Services: ANS and similar mechanisms provide globally unique, semantically rich, and versioned agent names (ANSNames), supporting capability-based and version-aware resolution (e.g., a2a://textProcessor.DocumentTranslation.AcmeCorp.v2.1.hipaa). Registry entries are secured by PKI-backed X.509 certificates with signatures, and trusted directory services sign endpoint records to guarantee integrity and authenticity (Huang et al., 15 May 2025).
• Topology-Independent Schemes: The agent:// URI scheme establishes a three-component name—organizational trust root, hierarchical capability path, and stable agent-id (sortable, lexicographically stable)—resolved via DHT key derivations. This design supports migration invariance, global agent referencing, and capability-oriented lookups, decoupled from network location (Rodriguez, 21 Jan 2026).
• Decentralized Peer-to-Peer Registries: Protocols such as DIAP eschew any central registry: agent identity is encoded as the IPFS Content-ID of an immutable DID document; agent ownership is proven via zero-knowledge proofs. Indexing/discovery occurs over resilient DHTs with cryptographic attestation and privacy-preserving mechanisms (Liu et al., 6 Nov 2025).

The combination of DIDs, verifiable directory entries, PKI (certificate chain validation), and cryptographic attestation enables high-assurance, scalable, and migration-tolerant discovery in open and federated multi-agent environments (Huang et al., 15 May 2025, Rodriguez, 21 Jan 2026).

3. Fine-Grained Access Control, Delegation, and Session Management

Agent IAM frameworks mandate real-time, context-aware access control mechanisms beyond coarse account-level models:

• Attribute-Based Access Control (ABAC): Policies are authored in expressive policy languages (e.g., Rego syntax) referencing agent DIDs, VCs, and contextual attributes such as action, resource, time, and location. The core permit decision is formalized as

$\Permit(\mathit{aid}, \mathit{res}, \mathit{act}) \;\Longleftarrow\; \Role(aid, "sensor") \wedge \mathit{Time}(\text{ctx})\in[09:00,17:00] \wedge \Capability(aid, \{\mathit{res}.\mathit{act}\})$

Agents present DIDs, VCs, and supporting proofs to Policy Decision Points (PDPs), which authorize or deny specific actions (Huang et al., 25 May 2025).

• Session Lifecycle and Revocation: Agents establish global sessions (GlobalSessionToken structures) post-authentication. Central authorities or distributed ledgers maintain real-time session states, revocation lists, and active token lifecycles—supporting immediate enforcement of policy changes and revocations across multiple protocol adapters (Huang et al., 25 May 2025).
• Delegation and Chained Authority: Systems like ACP formalize cryptographically verifiable, transitive delegation using parent_hash-anchored tokens and immutable audit trails. Each delegation step is Ed25519-signed and stateful, precluding privilege escalation or accidental over-delegation, with deterministic enforcement at every admission control check (Fernandez, 19 Mar 2026).
• Zero-Knowledge Authorizations: ZKPs are integrated for privacy-preserving attribute proof (e.g., threshold policies on credentials, age attestation) and compliance with selective disclosure or minimal exposure mandates (Huang et al., 25 May 2025, Liu et al., 6 Nov 2025).

These structures collectively enable multi-layered, cryptographically verifiable, and dynamically scoped agent action controls.

4. Security Properties, Threat Models, and Mitigations

The cryptographic primitives and protocol invariants are explicitly designed to resist canonical attacks endemic to autonomous systems:

1. Sybil Resistance: Agent registration is rate-limited and often anchored via initial trusted third-party VCs or enterprise-grade KYC credentials. Duplicate registration or identity inflation attacks are precluded by cryptographic uniqueness and external constraints (Huang et al., 25 May 2025).
2. Replay and Impersonation: All sensitive operations (registration, session, credential presentation) embed unique nonces, timestamps, and are subject to strong signature checks. Explicit checks on signature freshness, expiration, and nonce reuse prevent replay and impersonation (Huang et al., 25 May 2025, Fernandez, 19 Mar 2026).
3. Key and Credential Compromise: Immediate revocation workflow disables compromised DIDs, certificates, or VC IDs in registry or status list. Adapter Enforcement Middleware (AEM) and revocation push/synchronization ensure local sessions are promptly invalidated (Huang et al., 25 May 2025).
4. Registry Poisoning and Endpoint Integrity: Strong signature-based validation (PKI, Ed25519 signatures on endpoint records, registry entries, tokens) defend against registry manipulation. Integrity and authenticity checks are enforced for agent endpoint lookups and service interactions (Huang et al., 15 May 2025).
5. Accountability and Traceability: Immutable logs (potentially supported by Merkle inclusion proofs or blockchain event records) guarantee non-repudiable and tamper-evident trails from registration through every action and delegation step (Malkapuram et al., 22 Sep 2025, Fernandez, 19 Mar 2026).

A formal security posture is precipitated by tying every step—registration, action, delegation, revocation—to verifiable cryptographic operations, with Security Theorems underpinning resistance to common attack classes (Huang et al., 25 May 2025).

5. Ecosystem Integration, Practical Architectures, and Interoperability

Agent identity frameworks are integrated with existing IAM and PKI infrastructures, supporting broad interoperability:

• PKI and Certificate Lifecycle: ANS and similar schemes bind agent identity to X.509 certificates, issued and renewed by Registration Authorities and Certificate Authorities. Chains are validated at resolution, and revocation lists support swift cut-off of compromised keys (Huang et al., 15 May 2025).
• OAuth/OIDC Extensions: Protocols such as OIDC-A extend dynamic client registration and JWT claims to support agent-specific identifiers, capability declarations, delegation chains, and attestations. Registration flows, token and claim definitions, and delegation/attestation verifications are specified to ensure compatibility with OAuth 2.0 resource servers and authorization endpoints (Nagabhushanaradhya, 30 Sep 2025, South et al., 29 Oct 2025).
• Enterprise and Telco Integration: Telco-grade frameworks bind agent identity to eSIM profiles managed in hardware security modules by Mobile Network Operators. This leverages infrastructure-grade key control, attestation, and enterprise IAM integrations (SAML, SCIM, OAuth2/OIDC), achieving regulatory compliance and high throughput (Barros, 17 Apr 2025).
• Decentralized and Federated Registries: Architectures such as NANDA, AGNTCY Agent Directory, and DIAP provide decentralized, DHT-backed, verifiable lookup and attestation, functioning without centralized failure points or single administrative domains (Singh et al., 5 Aug 2025, Liu et al., 6 Nov 2025).
• Audit, Compliance, and Governance Models: Systems are designed for regulated and critical environments, with audit mechanisms (e.g., Merkle log proofs, signed tree heads), explicit trust anchors, human approval interleaving, and governance primitives for attribute, schema, and reputation management (Malkapuram et al., 22 Sep 2025, Xu, 15 Feb 2026).

Agent registration and identity are thereby positioned to support secure, scalable, and compliant MAS deployments across organizational and architectural boundaries.

6. Advanced Mechanisms: Zero-Knowledge, Execution Provenance, and Host-Independent Identity

Emergent protocols introduce advanced capabilities for privacy and compositional trust assertions:

• Zero-Knowledge Proofs: Agents may employ zk-SNARKs (e.g., Groth16) over arithmetic circuits for succinct, privacy-preserving attribute proofs—enabling selective disclosure (e.g., age ≥ 18), credential validity, or compliance claims without exposing underlying sensitive data (Huang et al., 25 May 2025, Liu et al., 6 Nov 2025).
• Host-Independent Execution Proofs: Architectures like VET define the Agent Identity Document (AID), which cryptographically declares an agent’s configuration and references compositional proof mechanisms (TEEs, SNARKs, notarized TLS transcripts). Every output is bound to a verifiable trace, allowing authenticable host-agnostic agent identity and non-forgeable provenance guarantees (Grigor et al., 17 Dec 2025).
• Recursive zkVM Proving for Code Binding: Frameworks such as BAID use recursive zkVMs to cryptographically bind operator identity, code configuration, and execution state. Proof chains anchor every execution to an on-chain registry entry, conferring code-substitution resistance and traceable accountability at the binary and execution levels (Lin et al., 19 Dec 2025).

These mechanisms provide a migration path for agent-centric systems requiring stringent privacy guarantees, host-agnostic authenticity, and full-state cryptographic provenance.

7. Comparative Overview and Future Directions

Agent registration and identity architectures are converging on several key principles: core identities rooted in asymmetric cryptography and DIDs; agent and capability registries supporting discovery and validation; composable, cryptographically enforced access and delegation models; real-time, tamper-evident session and revocation management; and extensibility via verifiable credentials, zero-knowledge proofs, and audit-anchored operational flows.

System selection—centralized (MCP), federated (OIDC-A, Entra), distributed (DIAP, NANDA, AGNTCY), or infrastructure-grade (eSIM, ACP)—must balance security, authentication, scalability, maintainability, and compliance as determined by the application domain (Singh et al., 5 Aug 2025, Fernandez, 19 Mar 2026, Barros, 17 Apr 2025). The field is advancing toward universal, verifiable interoperability across agent registries and discovery layers, with long-term challenges centered on privacy-accountability trade-offs, recursive delegation verification, content provenance, and seamless economic integration for autonomous agents (South et al., 29 Oct 2025, Xu, 15 Feb 2026).