XEP-0275: Entity Reputation

Abstract:This specification defines an XMPP protocol extension for communicating the reputation of any entity on the network.
Author:Peter Saint-Andre
Copyright:© 1999 - 2012 XMPP Standards Foundation. SEE LEGAL NOTICES.
Type:Standards Track
Last Updated:2010-01-21

WARNING: Consideration of this document has been Deferred by the XMPP Standards Foundation. Implementation of the protocol described herein is not recommended.

Table of Contents

1. Introduction
2. Terminology
3. Approach
    3.1. Server Reputation
    3.2. Account Reputation
    3.3. Other Entities
4. Protocol
5. Determining Support
6. Security Considerations
7. IANA Considerations
8. XMPP Registrar Considerations
    8.1. Protocol Namespaces
    8.2. Protocol Versioning
9. XML Schema
10. Acknowledgements

    A: Document Information
    B: Author Information
    C: Legal Notices
    D: Relation to XMPP
    E: Discussion Venue
    F: Requirements Conformance
    G: Notes
    H: Revision History

1. Introduction

Reputation systems are used in many online communities to increase trust and to encourage communication, commerce, and other forms of interaction. The public XMPP network might benefit from instituting a reputation system for servers, for end users, or both. The benefits might include fast blacklisting of rogue servers and other bad actors, differential quality of service based on reputation, delayed entry to Multi-User Chat [1] rooms for low-reputation users, integration with Privacy Lists [2], and the like.

2. Terminology

The following terms identify the entities mentioned in this document:

3. Approach

The approach taken here is that an XMPP entity (a "Subject") is innocent until proven guilty, so it starts out with a score of zero. Good behaviors will increase a Subject's score (up to a maximum of +127), whereas bad behaviors will decrease a Subject's score (potentially down to a minimum of -128). Any entity (a "Relying Party") can query another entity (a "Vouching Party") about the reputation score of a Subject. A Vouching Party might be a fellow IM user (e.g., a buddy in one's roster as defined in XMPP IM [3]), the server to which a client connects, a fellow server to which a server connects (see Server Buddies [4]), or a specialized reputation service (similar to a DNSBL on the email network). Changes in reputation scores can also be sent in real time to Relying Parties, either as part of Incident Reporting [5] or as separate notifications.

To determine reputation in an objective way, it is important to define the specific behaviors that are used as measurable dimensions of good or bad reputation. The following sections attempt to do so for XMPP servers and XMPP users, with some rough point values.

3.1 Server Reputation

On the theory that it is more important to reward positive behavior than to punish negative behavior, we first define a number of criteria for increasing the reputation score of an XMPP server (naturally this list of criteria is not meant to be exclusive).

Table 1: Positive Server Behaviors

Criterion Suggested Point Value
Presents a certificate issued by a recognized certification authority. +15
Requires CAPTCHAs or other hurdles for account registration (see CAPTCHA Forms [6]). +5
Supports XEP-0268: Incident Reporting. +5
Supports reputation scores for its users (i.e., this protocol). +5
Requires use of Transport Layer Security (TLS) for client-to-server connections. +5
Provides the _xmpp-client DNS SRV record. +5
Provides the _xmpp-server DNS SRV record. +5
Provides a website with accurate information and contact addresses. +5
Service answers Service Discovery [7] information requests sent to bare JIDs, including identification of admin accounts and anonymous users. +5
Administrator answers email sent to mailto:xmpp@domain.tld (see XMPP Core [8]) and takes appropriate actions to solve reported issues. +5
Time online (e.g., based on whois lookup or known deployment of an XMPP service). +3 for each year
Admin factor (average of admins' reputation scores, divided by ten and rounded up). Varies

For example, a server that (1) meets all of the foregoing criteria, (2) has been online for 7 years, and (3) whose admins have an average score of 37 would have a reputation number of 15+5+5+5+5+5+5+5+5+5+4+21 = 85.

By constrast, a server that does not have a CA-issued cert, does not require CAPTCHAs for account registration, does not support incident reporting, does not support reputation scores, does not require TLS, does have SRV records (+10), has no website, does not answer service discovery requests about its users, has not verified the xmpp@domain.tld email address, has been online for 1 week, and whose administrators are unknown would have a reputation score of 10.

3.2 Account Reputation

The reputation associated with an XMPP account (typically but not always a user) is harder to quantify and easier to fake than server reputation. The following are some possible criteria.

Table 2: Positive Account Behaviors

Criterion Suggested Point Value
Account has service discovery identity of account/admin +15
Account has service discovery identity of account/registered +5
Age of account +5 for each year
Verified email address +5
Verified website +5
Password strength Measured on a scale from 0 (e.g., "password") to 5
Reputation of buddies known to server Divide average reputation by 10
User has PGP key, X.509 certificate, or other public key +10
User has passed a CAPTCHA test (e.g., during account provisioning) +5
Chatroom ownership / administration For each room owned, divide room's reputation by 10; for each room administered, divide room's reputation by 20 (e.g., +6 and +3 for a room with a reputation of 60).
Chatroom banning For each room in which the user is banned (XEP-0045 "outcast"), divide the room's reputation by 10 and decrement the user's score by the result (e.g., -6 for a room with a reputation of 60).
Rate limiting For each rate limiting incident, -5.
Incident reports For each validated incident report, -10.

For example, an account that is an admin of a server (+15), has been online for 5 years (+25), has a verified email address (+5) and website (+5), has a strong password (+5), has a "buddy reputation average" of 40 (+4), uses a public key (+10), has passed a CAPTCHA test (+5), owns 3 chatrooms with an average reputation of 30 (+9), and has not been banned from any chatrooms, rate limited, or been the subject of any incident reports would have a reputation number of 83.

By contrast, an account that is registered (+5), was just created, has no verified email address or website, has a strong password (+5), has a "buddy reputation average" of 10 (+1), does not use a public key, has not passed a CAPTCHA test, owns or administers no chatrooms, has been banned from 3 chatrooms with an average reputation of 30 (-9), has been rate limited twice (-10), and has been the subject of 2 incident reports (-20) would have a reputation number of -28.

3.3 Other Entities

Any entity can have a reputation score: servers, end-user accounts, chatrooms, chatroom servers, publish-subscribe servers, vouching services, etc. Criteria for entities other than servers and accounts are yet to be described.

4. Protocol

In order to query a Vouching Party about the reputation of a Subject, a Relying Party sends an IQ stanza of type "get" containing a <score/> element qualified by the 'urn:xmpp:reputation:0' namespace (see Namespace Versioning regarding the possibility of incrementing the version number).

Example 1. Score request

<iq from='juliet@capulet.lit/chamber'
  <score xmlns='urn:xmpp:reputation:0' jid='romeo@montague.lit'/>

The Vouching Party would then return an error or a score.

Example 2. Score response

<iq from='shakespeare.lit'
  <score xmlns='urn:xmpp:reputation:0' 

Any XMPP error might be appropriate (e.g., <forbidden/> if the Relying Party is not trusted at all by the Vouching Party).

5. Determining Support

To advertise its support for reputation scores, when replying to Service Discovery [9] information requests an entity MUST return a feature for 'urn:xmpp:reputation:0'.

In order for an application to determine whether an entity supports this protocol, where possible it SHOULD use the dynamic, presence-based profile of service discovery defined in Entity Capabilities [10]. However, if an application has not received entity capabilities information from an entity, it SHOULD use explicit service discovery instead.

6. Security Considerations

Any entity can keep a reputation score for any other entity. Although some entities might be considered more knowledgeable than others, that judgment is up to the entity that makes a request for a reputation score and is not a feature of the network itself.

7. IANA Considerations

This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [11].

8. XMPP Registrar Considerations

8.1 Protocol Namespaces

This specification defines the following XML namespace:

Upon advancement of this specification from a status of Experimental to a status of Draft, the XMPP Registrar [12] shall add the foregoing namespace to the registry located at <http://xmpp.org/registrar/namespaces.html>, as described in Section 4 of XMPP Registrar Function [13].

8.2 Protocol Versioning

If the protocol defined in this specification undergoes a revision that is not fully backwards-compatible with an older version, the XMPP Registrar shall increment the protocol version number found at the end of the XML namespaces defined herein, as described in Section 4 of XEP-0053.

9. XML Schema

<?xml version='1.0' encoding='UTF-8'?>


  <xs:element name='score'>
        <xs:extension base='xs:string'>
          <xs:attribute name='jid' type='xs:string' use='required'/>
          <xs:attribute name='num' type='xs:byte' use='optional'/>


10. Acknowledgements

Thanks to Dan Brickley, Kevin Smith, Mike Taylor, and Matthew Wild for their feedback.


Appendix A: Document Information

Series: XEP
Number: 0275
Publisher: XMPP Standards Foundation
Status: Deferred
Type: Standards Track
Version: 0.1
Last Updated: 2010-01-21
Approving Body: XMPP Council
Dependencies: XMPP Core
Supersedes: None
Superseded By: None
Short Name: reputation
Source Control: HTML
This document in other formats: XML  PDF

Appendix B: Author Information

Peter Saint-Andre

Email: stpeter@jabber.org
JabberID: stpeter@jabber.org
URI: https://stpeter.im/

Appendix C: Legal Notices


This XMPP Extension Protocol is copyright © 1999 - 2012 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 <http://xmpp.org/about-xmpp/xsf/xsf-ipr-policy/> or obtained by writing to XMPP Standards Foundation, 1899 Wynkoop Street, Suite 600, Denver, CO 80202 USA).

Appendix D: Relation to XMPP

The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 3920) and XMPP IM (RFC 3921) 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 <http://xmpp.org/about/discuss.shtml> 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-0045: Multi-User Chat <http://xmpp.org/extensions/xep-0045.html>.

2. XEP-0016: Privacy Lists <http://xmpp.org/extensions/xep-0016.html>.

3. RFC 6121: Extensible Messaging and Presence Protocol (XMPP): Instant Messaging and Presence <http://tools.ietf.org/html/rfc6121>.

4. XEP-0267: Server Buddies <http://xmpp.org/extensions/xep-0267.html>.

5. XEP-0268: Incident Reporting <http://xmpp.org/extensions/xep-0268.html>.

6. XEP-0158: CAPTCHA Forms <http://xmpp.org/extensions/xep-0158.html>.

7. XEP-0030: Service Discovery <http://xmpp.org/extensions/xep-0030.html>.

8. RFC 6120: Extensible Messaging and Presence Protocol (XMPP): Core <http://tools.ietf.org/html/rfc6120>.

9. XEP-0030: Service Discovery <http://xmpp.org/extensions/xep-0030.html>.

10. XEP-0115: Entity Capabilities <http://xmpp.org/extensions/xep-0115.html>.

11. The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>.

12. The XMPP Registrar maintains a list of reserved protocol namespaces as well as registries of parameters used in the context of XMPP extension protocols approved by the XMPP Standards Foundation. For further information, see <http://xmpp.org/registrar/>.

13. XEP-0053: XMPP Registrar Function <http://xmpp.org/extensions/xep-0053.html>.

Appendix H: Revision History

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

Version 0.1 (2010-01-21)

Initial published version as accepted for publication by the XMPP Council; defined XML schema.


Version 0.0.1 (2010-01-11)

First draft.