AI Agent Identity: Authentication and Authority

An API key is not an agent identity

An AI agent identity is a durable record that distinguishes one autonomous workload from every other workload, connects it to an accountable owner, and gives policy systems a stable subject to evaluate. The identity should survive ordinary credential rotation. If replacing a token creates a new operational identity, attribution and history become fragmented exactly when an incident responder needs continuity.

A provider API key proves only that the caller possessed that provider key. When a team copies one key into five agents, the provider sees one credential and the team loses the ability to assign different scopes, budgets or off-switches. Log labels added by the agent are not a substitute because the same process that is being controlled can alter them.

Treat credentials as authentication material attached to an identity. The identity names the agent; the credential helps prove the caller currently controls that identity. This distinction allows a signing key or bearer token to be rotated, revoked or replaced without erasing ownership, policy, audit history or review dates.

Identity answers “which agent is this?” Authentication answers “how did it prove that?” Authority answers “what may it do now?”

What an agent identity record should contain

Start with a unique identifier, a human-readable name and an explicit owner. Add the agent's purpose, environment, lifecycle state, creation time and next review date. Record the authentication method honestly: a long-lived bearer token provides different assurance from a challenge signed by a private key. A security interface should not flatten those methods into the same trust label.

The record should also point to policy rather than embedding unlimited authority. Useful policy dimensions include provider, model, endpoint, tool, rate, token and cost limits. These attributes change more often than identity does. Keeping them separate makes it possible to narrow an agent's authority without issuing a new identity or losing the audit chain.

NIST's work on software-agent identity highlights the need to reason about identity and authority together. The Cloud Security Alliance similarly describes ownership, lifecycle management, least privilege and continuous governance as core agent-identity concerns. The practical consequence is simple: registration is the beginning of the lifecycle, not the entire control.

• Stable agent ID and descriptive name.
• Accountable person, team or service owner.
• Purpose, environment and expected capabilities.
• Authentication methods and credential status.
• Policy references, review date and lifecycle state.

Separate authentication from authorization

Authentication should happen before the requested capability is evaluated. The system verifies the presented token or cryptographic proof, resolves it to one active agent, and records the method used. Authorization then compares that agent's current policy with the requested provider, model, endpoint or tool. Passing authentication must never imply blanket access.

This separation matters when policy changes. A valid agent may be allowed to use a low-cost model but denied a more powerful one. It may call a read endpoint but not a write endpoint. It may have remaining daily budget but be blocked by a per-minute rate limit. These are current authority decisions, not properties that should be baked forever into a credential.

For high-assurance environments, asymmetric authentication reduces the value of a stolen database token because the private key remains with the workload. Bearer tokens are still useful for bootstrap and simpler deployments, but their possession model should be visible in the audit record. The safe design supports progressive assurance without pretending every method offers the same guarantees.

Make delegation narrow, explicit and traceable

Agent systems often form chains: an orchestrator asks a research agent for evidence, which asks another tool to retrieve data. Authority should not silently expand down that chain. A child workload needs its own identity or a narrowly scoped delegated grant that identifies the parent, the allowed action and an expiry. Copying the parent's credential turns a bounded task into inherited ambient authority.

Delegation should preserve both actors in the record. The system needs to answer which agent initiated the task, which agent executed the call, what authority was delegated and which policy allowed it. Chain-depth and retry limits help contain recursive workflows. Short expiry limits the harm if a delegated grant leaks after the task is complete.

Do not infer delegation from a string inside a prompt. Prompts are untrusted inputs and can be manipulated. Delegated authority belongs in a signed or server-issued security object that enforcement code validates independently of the model's narrative about what it is doing.

• Name both delegator and delegate.
• Limit destination, operation, budget and duration.
• Prevent the child from redelegating unless policy permits it.
• Record the complete chain without storing sensitive prompt content.

Operate identity as a lifecycle

Provision an identity only after an owner and purpose are known. Start with the narrowest useful scope and a modest budget. During operation, watch for denied calls, unusual destinations, authentication changes and cost anomalies. Review identities on a schedule and whenever ownership, environment or purpose changes.

Suspension and revocation solve different problems. Suspension stops the agent identity and all attached methods while preserving the record for investigation. Credential revocation invalidates one authentication method, which is useful during rotation or a suspected leak. Deletion should be rare because it can destroy the connection between historic evidence and the actor it described.

Offboarding needs a deterministic order: stop new authorization, revoke credentials, cancel outstanding delegated grants, preserve required audit evidence and then retire the identity. Test this path before an incident. If an operator cannot stop one agent quickly without rotating a fleet-wide provider key, the system does not yet have meaningful per-agent identity control.

Evaluate an identity system with evidence

Ask a candidate system to prove that two agents sharing one owner can have different scopes and budgets. Rotate one agent's authentication material and confirm its identity and history remain intact. Suspend it and verify both bearer and signing methods stop working before any upstream credential is retrieved. Then restore it without rewriting the audit trail.

Inspect the evidence produced by each decision. It should identify the stable agent, actual authentication method, requested capability, applied policy and outcome. Avoid systems whose audit relies on self-reported agent names or whose identity disappears when a token is deleted. Those designs make the controlled workload responsible for its own attribution.

PassControl implements one infrastructure-oriented model: a per-agent record owned by an account, bearer or cryptographic authentication, provider and model scopes, budgets, suspension, credential revocation and signed decision receipts. It does not establish the legal identity of a person, decide whether an agent's plan is wise, or replace workload sandboxing. Those remain separate controls.