TLDR
- Proof launched x401, an open protocol that verifies the human authority behind AI agent actions online.
- x401 pairs with x402 to cover the two core questions in agentic transactions: identity and payment.
- Proof Digital ID uses zero-knowledge proofs, letting users verify claims without exposing full identity.
- Proof will submit x401 to the FIDO Alliance’s agentic authentication standards workgroup for adoption.
Proof, an identity authorization company, has launched x401, an open protocol designed to verify the human authority behind AI agents.
As agents increasingly handle payments, contracts, and content publishing, the missing piece has been proof of who authorized them.
The x401 protocol addresses that gap directly, giving any website or API a standard way to request and verify identity credentials before permitting agent actions.
x401 Builds a Trust Layer for the Agentic Economy
The x401 protocol works by allowing services to request specific identity claims from an agent. These claims can include verified identity, age, organizational affiliation, or signing authority.
The agent then presents a compatible credential, and the service verifies the issuer, claim scope, and action before proceeding. This two-step process binds identity to authorization in a single verifiable proof.
Proof founder and CEO Pat Kinsel explained the broader shift driving the protocol’s creation. “AI is making actions and content effortless to generate,” Kinsel said.
“Trust will come from knowing who stands behind them.” He added that x401 gives every service a common way to ask for proof, while Proof Digital ID gives people and organizations a high-assurance way to answer.
The protocol is issuer-neutral by design. Any conforming issuer can deliver x401-compatible credentials, and every service decides independently which claims, issuers, and assurance levels it will accept. This approach avoids locking the internet into a single identity provider model.
Proof plans to submit x401 to the FIDO Alliance’s agentic authentication standards workgroup for broader industry adoption.
Proof’s Digital ID Delivers the First Live x401 Implementation
Proof is also releasing its own Digital ID product, the first live implementation capable of satisfying an x401 challenge.
It is built on Verifiable Credentials and supports the OID4VC Issuance and Presentation standard inline. Users can verify their identity to an IAL2 standard and re-authenticate with biometrics at any point.
Circle, one of the protocol’s co-endorsers, connected x401 to the existing x402 payment standard. Circle VP of Product Gagan Mac stated that “x402 answers how an agent pays, x401 answers who it is.”
Mac noted those are the first two questions any agentic transaction must clear, and both now have open standards.
The platform uses selective disclosure and zero-knowledge proofs. This means a person can prove nationality, age threshold, or organizational authority without exposing their full identity record. Developers request the identity claim, and Proof handles enrollment and verification behind the scenes.
Proof’s Digital ID also supports transaction signing. The API cryptographically binds a verified identity to payments, authorizations, or any signed payload.
These records serve as verifiable evidence of who authorized what, which many regulated industries now require. Full documentation is available at x401.id, with developer resources at dev.proof.com.