| Internet-Draft | Privacy Pass Reverse Flow HTTP Transport | June 2026 |
| Meunier | Expires 20 December 2026 | [Page] |
This document specifies an instantiation of Privacy Pass Reverse Flow [REVERSE-FLOW] where HTTP is used as a transport mechanism.¶
It describes a novel HTTP header field that Clients and Origins can use to carry reverse flow data.¶
This note is to be removed before publishing as an RFC.¶
The latest revision of this draft can be found at https://thibmeu.github.io/draft-meunier-privacypass-reverse-flow-informational/draft-meunier-privacypass-reverse-flow-http.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-meunier-privacypass-reverse-flow-http/.¶
Discussion of this document takes place on the Privacy Pass Working Group mailing list (mailto:privacy-pass@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/privacy-pass/. Subscribe at https://www.ietf.org/mailman/listinfo/privacy-pass/.¶
Source for this draft and an issue tracker can be found at https://github.com/thibmeu/draft-meunier-privacypass-reverse-flow-informational.¶
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.¶
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This Internet-Draft will expire on 20 December 2026.¶
Copyright (c) 2026 IETF Trust and the persons identified as the document authors. All rights reserved.¶
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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.¶
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.¶
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.¶
Below is an example request that uses [RFC9577] to pass the request Token, as well as PrivacyPass-Reverse for its reverse flow.¶
GET /foo HTTP/1.1 Host: example.com Authorization: PrivateToken token="abc..." PrivacyPass-Reverse: "def..." HTTP/1.1 200 OK PrivacyPass-Reverse: "001..." [BODY]¶
This document has no IANA actions.¶
TODO¶