Privacy Pass Reverse Flow HTTP Transport

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Table of Contents

1. Introduction

This document specifies an instantiation of Privacy Pass Reverse Flow [REVERSE-FLOW] where HTTP is used as a transport mechanism.¶

[REVERSE-FLOW] specifies an architecture in which a client can both present a token and initiate a new credential issuance flow.¶

As described in Section 4 of [REVERSE-FLOW], this requires in-band encoding of information used by the issuance protocol.¶

This document introduces a new HTTP header field as defined in [RFC9110]. This allows Clients to convey a CredentialRequest, and Origins to transmit a CredentialResponse.¶

2. Terminology

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. PrivacyPass-Reverse Header Field

A Client or an Origin following [REVERSE-FLOW] MAY include a PrivacyPass-Reverse header field to communicate Privacy Pass protocol data. This header field contains a base64url (per [BASE64]) encoded CredentialRequest or CredentialResponse.¶

GET /foo HTTP/1.1
Host: example.com
Authorization: PrivateToken token="abc..."
PrivacyPass-Reverse: "def..."

HTTP/1.1 200 OK
PrivacyPass-Reverse: "001..."

[BODY]

4. IANA Considerations

This document has no IANA actions.¶

5. References

Acknowledgments

TODO¶

Changelog

v00¶

• Initial draft¶

Author's Address