The "Payment" HTTP Authentication Scheme

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Table of Contents

1. Introduction

HTTP 402 "Payment Required" was reserved in HTTP/1.1 [RFC9110] for future use but never standardized. This specification defines the "Payment" authentication scheme that gives 402 concrete semantics.¶

A server requiring payment responds with 402 and a WWW-Authenticate: Payment challenge describing the payment requirements. The client fulfills the payment and retries with an Authorization: Payment credential. The server verifies the credential and grants access.¶

Payment methods, intents, and protocol details are defined in subsequent revisions of this document and companion specifications.¶

2. Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶

3. Security Considerations

Payment credentials authorize financial transactions and MUST be treated as sensitive bearer tokens. Implementations MUST use TLS for all Payment authentication flows. Detailed security analysis will be provided in a future revision.¶

4. IANA Considerations

This document registers the "Payment" authentication scheme in the "Hypertext Transfer Protocol (HTTP) Authentication Scheme Registry" established by [RFC9110]:¶

• Authentication Scheme Name: Payment¶

• Reference: This document¶

• Notes: Used with HTTP 402 for proof-of-payment flows¶

Future revisions will request creation of additional registries for payment methods and payment intents.¶

5. Normative References

[RFC2119]

Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>.

[RFC8174]

Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>.

[RFC9110]

Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke, Ed., "HTTP Semantics", STD 97, RFC 9110, DOI 10.17487/RFC9110, June 2022, <https://www.rfc-editor.org/info/rfc9110>.

Appendix A. Acknowledgements

TBD¶

Authors' Addresses