# Web Bot Auth HTTP Message Signatures (WebBotAuth) vs Security Principal and Verifier Binding for Agent Communication Protocols

They sit at the same step and overlap in purpose; the fields above are the basis for choosing.

[2 Identify](/category/identify/) [Web Bot Auth HTTP Message Signatures](/protocols/webbotauth/) · [2 Identify](/category/identify/) [Security Principal and Verifier Binding for Agent Communication Protocols](/protocols/agent-principal-binding/)

|  | [Web Bot Auth HTTP Message Signatures](/protocols/webbotauth/) WebBotAuth | [Security Principal and Verifier Binding for Agent Communication Protocols](/protocols/agent-principal-binding/) |
| --- | --- | --- |
| Lifecycle step | 2 Identify: Who is this agent? Who is this site? | 2 Identify: Who is this agent? Who is this site? |
| Answers | Which automated client made this HTTP request, and can the origin verify it cryptographically? | How can an agent communication protocol state, for each security-relevant claim (user authority, agent instance, tool identity, delegation, session, action evidence), which field carries it, which party verifies it, and what happens when it is absent, stale, or unverifiable? |
| Governed by | IETF webbotauth Working Group (chartered; document adopted as a WG item 2026-09-01) | Individual Internet-Draft submitted under BCP 78 and BCP 79; listed under the Agent Communication Protocols workgroup label. |
| Status (issuer's words) | Active Internet-Draft, WG Document, Intended Status: Standards Track; expires 5 March 2027 | Internet-Draft, Intended Status: Informational; expires 17 April 2027 |
| Version | draft-ietf-webbotauth-httpsig-protocol-00, adopted by the webbotauth WG, 2026-09-01 (replaces the individual draft-meunier-webbotauth-httpsig-protocol, last revision -02 of 2026-08-18) (2026-09-01) | draft-bu-agentproto-security-principal-binding-08 (2026-10-14) |
| Form / transport | HTTP header | document format |
| Found at | /.well-known/http-message-signatures-directory | none; a protocol-neutral review and specification-authoring model, not a wire protocol |
| Implementation | multi-implementation — Cloudflare (edge verification, verified-bots program) and independent client/server implementations listed in the draft's own appendix | none found |
| Evidence | 6 verified | 1 reported |
| Primary use case | Prove an agent's identity | Prove an agent's identity |
| Last verified | 2026-10-23 (current) | 2026-10-23 (current) |
| Specification | [https://datatracker.ietf.org/doc/draft-ietf-webbotauth-httpsig-protocol/](https://datatracker.ietf.org/doc/draft-ietf-webbotauth-httpsig-protocol/) | [https://datatracker.ietf.org/doc/html/draft-bu-agentproto-security-principal-binding-08](https://datatracker.ietf.org/doc/html/draft-bu-agentproto-security-principal-binding-08) |

## When to use which

- Choose Web Bot Auth HTTP Message Signatures when your question is “Which automated client made this HTTP request, and can the origin verify it cryptographically?” and you accept its maturity: status "Active Internet-Draft, WG Document, Intended Status: Standards Track; expires 5 March 2027", implementation multi-implementation (Cloudflare (edge verification, verified-bots program) and independent client/server implementations listed in the draft's own appendix).
- Choose Security Principal and Verifier Binding for Agent Communication Protocols when your question is “How can an agent communication protocol state, for each security-relevant claim (user authority, agent instance, tool identity, delegation, session, action evidence), which field carries it, which party verifies it, and what happens when it is absent, stale, or unverifiable?” and you accept its maturity: status "Internet-Draft, Intended Status: Informational; expires 17 April 2027", implementation none found.

Guidance is derived from the two records (question, status, implementation, prerequisites, pairings), not from opinion. Each record's page carries its numbered references.

## Read the full articles

- [Web Bot Auth HTTP Message Signatures](/protocols/webbotauth/): Which automated client made this HTTP request, and can the origin verify it cryptographically?
- [Security Principal and Verifier Binding for Agent Communication Protocols](/protocols/agent-principal-binding/): How can an agent communication protocol state, for each security-relevant claim (user authority, agent instance, tool identity, delegation, session, action evidence), which field carries it, which party verifies it, and what happens when it is absent, stale, or unverifiable?

Ask the MCP server to compare any two: the compare-protocols prompt, or get on both ids. [Connect](/connect/).

[webbotauth.json](/data/protocols/webbotauth.json) · [agent-principal-binding.json](/data/protocols/agent-principal-binding.json) · [Markdown](/compare/webbotauth-vs-agent-principal-binding/index.md)