XEP-0476: Pubsub Signing: OpenPGP Profile

Specifies a pubsub signing profile for OpenPGP
Jérôme Poisson
© 1999 – 2021 XMPP Standards Foundation. SEE LEGAL NOTICES.


WARNING: This Standards-Track document is Experimental. Publication as an XMPP Extension Protocol does not imply approval of this proposal by the XMPP Standards Foundation. Implementation of the protocol described herein is encouraged in exploratory implementations, but production systems are advised to carefully consider whether it is appropriate to deploy implementations of this protocol before it advances to a status of Draft.
Standards Track
0.1.0 (2022-12-20)
Document Lifecycle
  1. Experimental
  2. Proposed
  3. Stable
  4. Final

1. Introduction

This XMPP extension protocol specifies a profile of Pubsub Signing to use OpenPGP for signature.

2. Signing a Pubsub Item With OpenPGP

Signing an item with OpenPGP requires to have OpenPGP for XMPP (XEP-0373) [1] implemented to handle keys, however this specification uses its own <sign/> element because it uses wrapper element from Pubsub Signing XEP, and signed data MUST NOT be included with the signature.

To sign an element, a client process as explained in XEP-0XXX § Signing a Pubsub Item where the "signing profile" element used is a <sign/> element qualified by the 'urn:xmpp:pubsub-signing:openpgp:0' namespace. This element MUST contain a Base64 encoded (RFC 4648 [2] § 4) OpenPGP message as specified in RFC 4880 [3] which MUST contain a detached signature as defined in RFC 4880 [3] § 11.4 of the signed data as specified in XEP-0XXX § Signing a Pubsub Item.

Example 1. Juliet Publishes Her Signature as an Attachment With OpenPGP Signing Profile
<iq xmlns="jabber:client" from="juliet@capulet.lit/chamber" to="juliet@capulet.lit" id="signature_1" type="set">
  <pubsub xmlns="http://jabber.org/protocol/pubsub">
    <items node="urn:xmpp:pubsub-attachments:1/xmpp:juliet@capulet.lit?;node=urn%3Axmpp%3Amicroblog%3A0;item=random-thoughts-12bd">
      <item id="juliet@capulet.lit">
        <attachments xmlns="urn:xmpp:pubsub-attachments:1">
          <signature xmlns="urn:xmpp:pubsub-signing:0">
            <time stamp="2022-10-16T18:39:03Z"/>
            <sign xmlns="urn:xmpp:pubsub-signing:openpgp:0">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</sign>

3. Discovering Support

If a client supports the protocol specified in this XEP, it MUST advertise it by including the "urn:xmpp:pubsub-signing:openpgp:0" discovery feature in response to a Service Discovery (XEP-0030) [4] information request:

Example 2. Service Discovery information request
<iq type='get'
  <query xmlns='http://jabber.org/protocol/disco#info'/>
Example 3. Service Discovery information response
<iq type='result'
  <query xmlns='http://jabber.org/protocol/disco#info'>
    <feature var='urn:xmpp:pubsub-signing:openpgp:0'/>

4. Security Considerations

Security considerations of OpenPGP for XMPP (XEP-0373) [1] and XEP-0XXX apply.

5. IANA Considerations


6. XMPP Registrar Considerations


7. XML Schema


8. Acknowledgements

Thanks to NLnet foundation/NGI0 Discovery for funding.


Appendix A: Document Information

XMPP Standards Foundation
Standards Track
Last Updated
Approving Body
XMPP Council
XMPP Core, XEP-0001, XEP-0004, XEP-0060, XEP-0373
Superseded By
Short Name
Source Control

This document in other formats: XML  PDF

Appendix B: Author Information

Jérôme Poisson


This XMPP Extension Protocol is copyright © 1999 – 2020 by the XMPP Standards Foundation (XSF).


Permission is hereby granted, free of charge, to any person obtaining a copy of this specification (the "Specification"), to make use of the Specification without restriction, including without limitation the rights to implement the Specification in a software program, deploy the Specification in a network service, and copy, modify, merge, publish, translate, distribute, sublicense, or sell copies of the Specification, and to permit persons to whom the Specification is furnished to do so, subject to the condition that the foregoing copyright notice and this permission notice shall be included in all copies or substantial portions of the Specification. Unless separate permission is granted, modified works that are redistributed shall not contain misleading information regarding the authors, title, number, or publisher of the Specification, and shall not claim endorsement of the modified works by the authors, any organization or project to which the authors belong, or the XMPP Standards Foundation.

Disclaimer of Warranty

## NOTE WELL: This Specification is provided on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. ##

Limitation of Liability

In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall the XMPP Standards Foundation or any author of this Specification be liable for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if the XMPP Standards Foundation or such author has been advised of the possibility of such damages.

IPR Conformance

This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which can be found at <https://xmpp.org/about/xsf/ipr-policy> or obtained by writing to XMPP Standards Foundation, P.O. Box 787, Parker, CO 80134 USA).

Visual Presentation

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Appendix D: Relation to XMPP

The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 6120) and XMPP IM (RFC 6121) specifications contributed by the XMPP Standards Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this document has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.

Appendix E: Discussion Venue

The primary venue for discussion of XMPP Extension Protocols is the <standards@xmpp.org> discussion list.

Discussion on other xmpp.org discussion lists might also be appropriate; see <https://xmpp.org/community/> for a complete list.

Errata can be sent to <editor@xmpp.org>.

Appendix F: Requirements Conformance

The following requirements keywords as used in this document are to be interpreted as described in RFC 2119: "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL".

Appendix G: Notes

1. XEP-0373: OpenPGP for XMPP <https://xmpp.org/extensions/xep-0373.html>.

2. RFC 4648: The Base16, Base32, and Base64 Data Encodings <http://tools.ietf.org/html/rfc4648>.

3. RFC 4880: OpenPGP Message Format <http://tools.ietf.org/html/rfc4880>.

4. XEP-0030: Service Discovery <https://xmpp.org/extensions/xep-0030.html>.

Appendix H: Revision History

Note: Older versions of this specification might be available at https://xmpp.org/extensions/attic/

  1. Version 0.1.0 (2022-12-20)
    Accepted by vote of Council on 2022-11-30.
    XEP Editor (jsc)
  2. Version 0.0.1 (2022-10-29)

    First draft.


Appendix I: Bib(La)TeX Entry

  title = {Pubsub Signing: OpenPGP Profile},
  author = {Poisson, Jérôme},
  type = {XEP},
  number = {0476},
  version = {0.1.0},
  institution = {XMPP Standards Foundation},
  url = {https://xmpp.org/extensions/xep-0476.html},
  date = {2022-10-29/2022-12-20},