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Web Bot Auth (Signed Agents)(WBA)
An emerging IETF-draft standard (Cloudflare and Google) that lets an agent cryptographically prove its identity to a website using RFC 9421 HTTP Message Signatures. The agent signs each outbound request with an Ed25519 key, publishes its public keys as a JWKS key directory at /.well-known/http-message-signatures-directory, and points to it with a Signature-Agent header; the origin fetches the directory, verifies the signature, and decides whether to allow, deny, rate-limit, or price the traffic. It replaces brittle IP-range and User-Agent allowlists, and Cloudflare's Signed Agents productizes it at the edge. Distinct from authenticated-delegation: that proves user-to-agent authority, whereas Web Bot Auth is the inverse, an agent proving its origin to a website.
In 30 seconds
- What
- Agent cryptographically signs each HTTP request with Ed25519, publishes public keys at /.well-known/http-message-signatures-directory, and origin verifies signature to allow, deny, rate-limit, or price traffic.
- When to use
- Origins need to distinguish legitimate agents from scrapers and grant different access tiers based on verified agent identity rather than spoofable IP ranges or User-Agent headers.
- Watch out
- Key rotation and expiry window management become operational burdens; misconfigured signature validation opens doors to replay attacks or signature forgery if not implemented precisely.
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Web Bot Auth (Signed Agents): Overview
An emerging IETF-draft standard (Cloudflare and Google) that lets an agent cryptographically prove its identity to a website using RFC 9421 HTTP Message Signatures. The agent signs each outbound request with an Ed25519 key, publishes its public keys as a JWKS key directory at /.well-known/http-message-signatures-directory, and points to it with a Signature-Agent header; the origin fetches the directory, verifies the signature, and decides whether to allow, deny, rate-limit, or price the traffic. It replaces brittle IP-range and User-Agent allowlists, and Cloudflare's Signed Agents productizes it at the edge. Distinct from authenticated-delegation: that proves user-to-agent authority, whereas Web Bot Auth is the inverse, an agent proving its origin to a website.
- Agent signs each request with RFC 9421 HTTP Message Signatures (Ed25519)
- Public keys published as a JWKS directory at /.well-known/http-message-signatures-directory
- Signature-Agent header points the origin to the key directory
- Short expiry windows on signatures limit replay attacks
- Origins allow, deny, rate-limit, or price verified agent traffic
- Replaces spoofable IP-range and User-Agent allowlists
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References
The papers, specifications, and repositories this pattern is based on.
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