Agent Auth by Vigil bronze

www.bysigil.com

“Decentralized identity infrastructure for AI agents. DID-based authentication using Ed25519 keypairs and challenge-response, issuing Verifiable Credentials (VC-JWT). Supports both headless API flow (no browser) and hosted sign-in page.

a2a https://auth.usevigil.dev talk to it https://www.bysigil.com/.well-known/agent.json its card

Checked 1d ago pushNotifications, streaming

we checked this the operator says this

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Verified by agenttru.st

Everything here is a check agenttru.st performed itself. Assurance, protocol, hosting and freshness are in the card above and are not repeated.

Certificate: Issued by Google Trust Services domain-validated
Valid until 19 Jan 2027 as of our check on 13 Nov 2026.

Control of the hostname was checked; nothing about who operates it.

Key ECDSA P-256, signed ECDSA-SHA256, issued via WE1 under GTS Root R4 — classical, as every publicly trusted certificate is today.

Names on this certificate (1)

www.bysigil.com.
Connection: TLS 1.3 · X25519MLKEM768 — post-quantum hybrid key exchange, agreed with our checker on 13 Nov 2026. What this means
DANE / TLSA: Not verified
Discovery: Well-known document
AI-facing documents: Publishes /llms.txt — “Agent Auth by Vigil — Identity for AI Agents” a curated map of the site's content for language models

Fetched from this host during verification. Neither document is how this agent was discovered.
First seen: 6 Nov 2026

View verification details

Assurance: bronze Bronze — agent card fetched over HTTPS with a valid certificate
Protocols: A2A verified by handshake or card fetch, not merely advertised
Hosted in: ? Unknown · Cloudflare, Inc. (AS13335)
The address did not geolocate — usually anycast hosting, where one address answers from many places at once.
Last checked: 1d ago

What this agent says it can do

Declared in the agent's own card. agenttru.st has not tested whether it completes any of these tasks — the operator of www.bysigil.com controls every word below.

Register DID Identity

Register a new agent DID identity with an Ed25519 public key. The server can generate the keypair (returns private_key_jwk and key_origin: server_generated), or you can supply your own public key via public_key_jwk (BYOK, key_origin: client_provided). Returns a did:key identifier and a Verifiable Credential.

Request Auth Challenge

Request a cryptographic challenge for DID-based authentication. Returns a challenge_id and a one-time nonce (valid 60 seconds) to be signed with the agent's Ed25519 private key as UTF-8 bytes.

Verify Signed Challenge

Submit a signed challenge to authenticate. Provide challenge_id, did, and base64url-encoded Ed25519 signature of the nonce (signed as UTF-8). Returns a session token (valid 1 hour) and a Verifiable Credential (VC-JWT, valid 24 hours).

Verify Agent Credential

Verify a Verifiable Credential (VC-JWT) issued by Agent Auth by Vigil. Returns the agent's verified identity including did, agent_name, agent_model, agent_provider, agent_purpose, key_fingerprint, and key_origin (server_generated or client_provided).

Headless Authentication Flow

Complete headless API authentication for AI agents (no browser required). Steps: (1) POST /v1/identities to register and get a keypair, (2) POST /v1/auth/challenge to get a nonce, (3) sign the nonce as UTF-8 bytes with your Ed25519 private key, (4) POST /v1/auth/verify to receive a Verifiable Credential. The credential can then be presented to any trusting website.

agenttru.st compared this card's skill list with every other listing's: 3 other listings declare an identical one, ignoring case, spacing and each card's own hostname. See all 4. That says the cards' text is the same, not who runs them.

Technical agent card

Copied from the agent's card. The operator controls these values; agenttru.st has not verified them.

Provider: Agent Auth by Vigil — what this agent says about itself; other agents claiming the same provider are not thereby related
Protocol: a2a
Version: 0.4.1
Card completeness: a2a.proto v1.0 requires eight top-level fields. This card omits:
supportedInterfaces

Missing fields do not affect listing — they describe how much the operator has published, not whether the agent was verified.

View all card details

Capabilities: pushNotifications streaming
Agent card: https://www.bysigil.com/.well-known/agent.json

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