---
title: "HTTP Message Signatures, defined | Agent Ready Checkout"
description: "HTTP Message Signatures: RFC 9421: a way to sign selected HTTP components, carried in Signature-Input and Signature headers."
canonical: https://agentreadycheckout.com/glossary/http-message-signatures
site: "Agent Ready Checkout"
last_updated: 2026-11-04
section: "Glossary"
---

# HTTP Message Signatures, defined | Agent Ready Checkout

> HTTP Message Signatures: RFC 9421: a way to sign selected HTTP components, carried in Signature-Input and Signature headers.

Source: https://agentreadycheckout.com/glossary/http-message-signatures
Site: Agent Ready Checkout
Last reviewed: 2026-11-04

Glossary

# HTTP Message Signatures

In short

HTTP Message Signatures: RFC 9421: a way to sign selected HTTP components, carried in Signature-Input and Signature headers. The sourced facts on this site do not use HTTP Message Signatures outside this entry. Example: Cloudflare checks created, expires, nonce and tag in Signature-Input before verifying an Ed25519 signature. After HTTP Message Signatures the glossary lists Visa Intelligent Commerce.

## Definition

RFC 9421: a way to sign selected HTTP components, carried in Signature-Input and Signature headers.

## Example

Cloudflare checks created, expires, nonce and tag in Signature-Input before verifying an Ed25519 signature. [blog.cloudflare.com](https://blog.cloudflare.com/secure-agentic-commerce/), read 4 Nov 2026.

## Nearby terms

-   [Visa Intelligent Commerce](https://agentreadycheckout.com/glossary/visa-intelligent-commerce)
-   [Intelligent Commerce Connect](https://agentreadycheckout.com/glossary/intelligent-commerce-connect)
-   [Web Bot Auth](https://agentreadycheckout.com/glossary/web-bot-auth)
-   [All terms](https://agentreadycheckout.com/glossary)

## Sources

1.  [Cloudflare: Secure agentic commerce](https://blog.cloudflare.com/secure-agentic-commerce/), read 4 Nov 2026

Last reviewed 4 Nov 2026

## Edition

Matrix edition of 4 Nov 2026.

Reviewed 4 Nov 2026, [1 sources](#sources-h).

## Method

[How cells, sources and read dates are defined](https://agentreadycheckout.com/method)