# RFC 9421 signed requests

HTTP Message Signatures: the agent signs a canonical set of headers with its private key, and you verify against its published public key. Same idea as SSL for a request body — it proves origin and blocks replay. This is the trust primitive of the machine economy.

Canonical: https://robauto.ai/learn/agentic-commerce-101/11

_Agentic Commerce 101: How Agents Buy and Sell — lesson 11 of 20 (DEFINITION)_

HTTP Message Signatures: the agent signs a canonical set of headers with its private key, and you verify against its published public key. Same idea as SSL for a request body — it proves origin and blocks replay. This is the trust primitive of the machine economy.

Source: [IETF RFC 9421](https://www.rfc-editor.org/rfc/rfc9421.html?utm_source=robauto)

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