REPUTE Working Group                                       N. Borenstein
Internet-Draft                                                  Mimecast
Intended status: Standards Track                            M. Kucherawy
Expires: December 30, 2012                                 June 28, May 17, 2013                                  November 13, 2012

                A Media Type for Reputation Interchange


   This document defines a media type for exchanging reputation
   information about an arbitrary class of object.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on December 30, 2012. May 17, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   ( in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology and Definitions  . . . . . . . . . . . . . . . . .  3
     2.1.  Key Words  . . . . . . . . . . . . . . . . . . . . . . . .  3
     2.2.  Other Definitions  . . . . . . . . . . . . . . . . . . . .  3
   3.  Description  . . . . . . . . . . . . . . . . . . . . . . . . .  3
     3.1.  Reputon Keys . . . . . . . . . . . . . . . . . . . . . . .  4
     3.2.  Reputon Structure  . . . . . . . . . . . . . . . . . . . .  5
     3.3.  Example Reply  . . . . . . . . . . . . . . . . . . . . . .  6
   4.  Scores . . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
     5.1.  application/reputon Media Type Registration  . . . . . . .  8
     5.2.  Reputation Applications Registry . . . . . . . . . . . . .  9
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     7.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 11
   Appendix A.  Acknowledgments . . . . . . . . . . . . . . . . . . . 12
   Appendix B.  Public Discussion . . . . . . . . . . . . . . . . . . 12
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12

1.  Introduction

   This document defines a media type for use when answering a
   reputation query using the "long form" query defined in
   [I-D.REPUTE-QUERY-HTTP], which uses [HTTP].

   Also included is the specification for an IANA registry to contain
   definitions and symbolic names for known reputation applications and
   corresponding response sets.

2.  Terminology and Definitions

   This section defines terms used in the rest of the document.

2.1.  Key Words

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [KEYWORDS].

2.2.  Other Definitions

   Other terms of importance in this document are defined in
   [I-D.REPUTE-MODEL], the base document in this document series.

3.  Description

   A "reputon" is a single independent object containing reputation
   information.  A particular query about a subject of interest will
   receive one or more reputons in response, depending on the nature of
   the data collected and reported by the server.

   The format selected for the representaton of a reputon is Javascript
   Object Notation (JSON), defined in [JSON].  Accordingly, a new media
   type, "application/reputon+json", is defined for the JSON
   representation of reputational data, typically in response to a
   client making a request for such data about some subject.  This media
   type has one optional parameter, "app", which defines the specific
   reputation application in whose context the query is made and the
   response returned.  If absent, a generic reputation query is assumed
   for which only a simple reply is allowed.

   The body of the media type consists of a JSON document that contains
   the reputation information requested.  A detailed description of the
   expected structure of the reply is provided below.

3.1.  Reputon Keys

   The key pieces of data found in a reputon for all reputation
   applications are defined as follows:

   RATER:  The identity of the entity providing the reputation
      information, typically expressed as a DNS domain name.

   ASSERTION:  A keyword indicating the specific assertion or claim
      being rated.  In the absence of an "app" parameter on the media
      type, the reputon can only indicate generic goodness, with the
      default assertion "IS-GOOD," but each application is expected to
      define additional ASSERTIONs.

   RATED:  The identity of the entity being rated.  The nature of this
      field is application-specific; it could be domain names, email
      addresses, driver's license numbers, or anything that uniquely
      identifies the entity being rated.  Documents that define specific
      reputation applications are required to define syntax and
      semantics for this field.

   RATING:  The overall rating score for that entity, expressed as a
      floating-point number between 0.0 and 1.0 inclusive.  See
      Section 4 for discussion.

   The following are OPTIONAL for all applications, to be used in
   contexts where they are appropriate:

   CONFIDENCE:  The level of confidence the reputation provider has in
      the value presented being accurate, expressed as a floating-point
      number between 0.0 and 1.0 inclusive.

   RATER-AUTHENTICITY:  The level of confidence in that identity being
      genuine, expressed as a floating-point number between 0.0 and 1.0

   SAMPLE-SIZE:  The number of data points used to compute that score,
      possibly an approximation.  Expressed as an unsigned 64-bit
      integer.  The units are deliberately not specified, since not all
      reputation service providers will collect data the same way.
      Consumers will need to determine out-of-band the units being
      reported and apply this value accordingly within their local

   UPDATED:  A timestamp indicating when this value was generated.
      Expressed as the number of seconds since January 1, 1970 00:00

   A particular application that registers itself with IANA MAY also
   define additional application-specific attribute/value pairs beyond
   these standard ones.

   Further, particular application service providers MAY provide local
   extensions to registered applications.  Syntax for these will need to
   be specified and accommodated privately between clients and servers.

3.2.  Reputon Structure

   A reputon expressed in JSON consists of an object that itself
   contains zero or more objects whose names are "reputon".  Each
   reputon object is a set of key-value pairs, where the keys are the
   names of particular properties that comprise a reputon (as listed
   above, or as provided with specific applications), and values are the
   content associated with those keys.  The set of keys that make up a
   reputon within a given application are known as that application's
   "response set".

   Thus, the following simple example:

     Content-type: application/reputon+json

         "rater": "",
         "rater-authenticity": 1.0,
         "assertion": "IS-GOOD",
         "rated": "Alex Rodriguez",
         "rating": 0.99,
         "sample-size": 50000

   ...indicates we are absolutely sure (1.0) that the entity
   "" consolidated 50000 data points (perhaps from
   everyone in Yankee Stadium) and concluded that Alex Rodriguez is very
   very good (0.99) at something.  It doesn't tell us what he's good at,
   and while it might be playing baseball, it could just as well be
   paying his taxes on time.

   A more sophisticated usage would define a baseball application with a
   response set of specific assertions, so that this example:

     Content-type: application/reputon+json; app="baseball"

         "rater": "",
         "rater-authenticity": 1.0,
         "assertion": "HITS-FOR-POWER",
         "rated": "Alex Rodriguez",
         "rating": 0.99,
         "sample-size": 50000

   ...would indicate that 50000 fans polled by the entity baseball- rate A-Rod very highly in hitting for power,
   whereas this example:

     Content-type: application/reputon+json; app="baseball"

         "RATER": "",
         "RATER-AUTHENTICITY": 1.0,
         "RATED": "Alex Rodriguez",
         "RATING": 0.4,
         "SAMPLE-SIZE": 50000

   ...would indicate that a similar poll indicated a somewhat weaker
   consensus that A-Rod tends to choke in critical baseball situations.

   In practice, most usage of reputons is expected to make use of the
   "app" parameter to target an application-specific set of assertions.

3.3.  Example Reply

   The following is an example reputon generated using this schema,
   including the media type definition line:

     Content-Type: application/reputon+json; app="email-id"

         "rater": "",
         "rater-authenticity": 0.95,
         "assertion": "SPAM",
         "identity": "DKIM",
         "rated": "",
         "rating": 0.012,
         "sample-size": 16938213,
         "updated": 1317795852

   Here, reputation agent "" is asserting within the
   context of the "email-id" application that "" appears to
   be associated with spam 1.2% of the time, based on just short of 17
   million messages analyzed or reported to date.  The "email-id"
   application has declared the extension key "identity" to indicate how
   the subject identifier was used in the observed data, establishing
   some more specific semantics for the "rating" value.  In this case,
   the extension is used to show the identity "", the subject
   of the query, is extracted from the analyzed messages using the
   [DKIM] "d=" parameter for messages where signatures validate.  The
   reputation agent is 95% confident of this result.  (See
   [I-D.REPUTE-EMAIL-IDENTIFIERS] for details about the registered email
   identifiers application.)

4.  Scores

   The score presented as the value in the RATING parameter appears as a
   floating point value between 0.0 and 1.0 inclusive.  The intent is
   that the definition of an assertion within an application will
   declare what the anchor values 0.0 and 1.0 specifically mean.
   Generally speaking, 1.0 implies full agreement with the assertion,
   while 0.0 indicates no support for the assertion.

   The definition will also specify the type of scale in use when
   generating scores, to which all reputation service providers for that
   application space must adhere.  This will allow a client to change
   which reputation service provider is being queried for a given
   without having to learn through some out-of-band method what the new
   provider's values mean.  For example, a registration might state that
   ratings are linear, which would mean a score of "x" is twice as
   strong as a value of "x/2".

5.  IANA Considerations

   This document presents two actions for IANA, namely the creation of
   the new media type "application/reputon+json" and the creation of a
   registry for reputation application types.  Another document in this
   series creates an initial registry entry for the latter.

5.1.  application/reputon Media Type Registration

   This section provides the media type registration application from
   [MIME-REG] for processing by IANA:


   Subject:  Registration of media type application/reputon

   Type name:  application

   Subtype name:  reputon+json

   Required parameters:  none

   Optional parameters:

      app:  Names the reputation application in use within the reputon,
         which defines the valid assertions and any extensions that may
         also be valid (i.e., the response set) for that application.
         These MUST be registered with IANA.

   Encoding considerations:  "7bit" encoding is sufficient and MUST be
      used to maintain readability when viewed by non-MIME mail readers.

   Security considerations:  See Section 6 of [this document].

   Interoperability considerations:  Implementers MUST ignore any "app"
      values, attribute/value pairs, or response set items they do not

   Published specification:  [this document]

   Applications that use this media type:  Any application that wishes
      to query a service that provides reputation data using the "long
      form" defined in [I-D.REPUTE-QUERY-HTTP].  The example application
      is one that provides reputation expressions about DNS domain names
      found in email messages.

   Additional information:  The value of the "app" parameter MUST also
      be registered with IANA.

   Person and email address to contact for further information:

         Nathaniel Borenstein <>

         Murray S. Kucherawy <>

   Intended usage:  COMMON


         Nathaniel Borenstein

         Murray S. Kucherawy

   Change controller:  IESG

5.2.  Reputation Applications Registry

   IANA is requested to create the "Reputation Applications" registry.
   This registry will contain names of applications used with the
   application/reputon+json media type (and other media types that carry
   reputons), as defined by this document.

   New registrations or updates MUST be published in accordance with the
   "Specification Required" guidelines as described in

   New registrations and updates are to contain the following

   1.  Name of the application being registered or updated

   2.  Short description of the application (i.e., the class of entity
       about which it reports reputation data)

   3.  The document in which the application is defined

   4.  New or updated status, which is to be one of:

       current:  The application is in current use

       deprecated:  The application is in current use but its use is

       historic:  The application is no longer in current use

   5.  A description of the subject of a query within this reputation,
       and a legal syntax for the same

   6.  An optional table of query parameters that are specific to this
       application; each table entry must include:

       Name:  Name of the query parameter

       Status:  (as above)

       Description:  A short description of the purpose of this

       Syntax:  A reference to a description of valid syntax for the
          parameter's value

       Required:  "yes" if the parameter is mandatory, "no" otherwise

   7.  A list of one or more assertions registered within this
       application; each table entry is to include:

       Name:  Name of the assertion

       Description:  A short description of the assertion, with specific
          meanings for values of 0.0 and 1.0

       Scale:  A short description of the scale used in computing the
          value (see Section 4 of this document)

   8.  An optional list of one or more response set extension keys for
       use within this application; each table entry is to include:

       Name:  Name of the extension key

       Description:  A short description of the key's intended meaning

       Syntax:  A description of valid values that can appear associated
          with the key

6.  Security Considerations

   This section describes document is primarily an IANA action registering a media type.
   It does not describe a new protocol that might introduce security considerations introduced by

   Discussion of the
   media type security and content syntax defined here.

   [TBD] operational impacts of using
   reputation services in general can be found throughout

7.  References

7.1.  Normative References

              Borenstein, N. and M. Kucherawy, "A Model for Reputation
              Interchange", draft-ietf-repute-model (work in progress),
              June 2011.
              November 2012.

              Borenstein, N. and M. Kucherawy, "Reputation Data
              Interchange using HTTP and XML",
              draft-ietf-repute-query-http (work in progress),
              November 2011. 2012.

   [JSON]     Crockford, D., "The application/json Media Type for
              JavaScript Object Notation (JSON)", RFC 4627, July 2006.

              Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

7.2.  Informative References

   [DKIM]     Crocker, D., Ed., Hansen, T., Ed., and M. Kucherawy, Ed.,
              "DomainKeys Identified Mail (DKIM) Signatures", RFC 6376,
              September 2011.

   [HTTP]     Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

              Kucherawy, M., "Operational Considerations Regarding
              Reputation Services", draft-ietf-repute-model (work in
              progress), November 2012.

              Borenstein, N. and M. Kucherawy, "A Reputation Vocabulary
              for Email Identifiers",
              draft-ietf-repute-email-identifiers (work in progress),
              November 2011. 2012.

              Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", RFC 5226, May 2008.

              Freed, N. and J. Klensin, "Media Type Specifications and
              Registration Procedures", RFC 4288, December 2005.

Appendix A.  Acknowledgments

   The authors wish to acknowledge the contributions of the following to
   this specification: Frank Ellermann, Tony Hansen, Jeff Hodges, John
   Levine, David F. Skoll, and Mykyta Yevstifeyev.

Appendix B.  Public Discussion

   Public discussion of this suite of documents takes place on the mailing list.  See

Authors' Addresses

   Nathaniel Borenstein
   203 Crescent St., Suite 303
   Waltham, MA  02453

   Phone: +1 781 996 5340

   Murray S. Kucherawy
   2063 42nd Avenue
   San Francisco, CA  94116