[Docs] [txt|pdf|xml] [Tracker] [Email] [Nits]

Versions: 00 01 02

Network Working Group                                       A. Mayrhofer
Internet-Draft                                                 D. Klesev
Updates: 7553 (if approved)                                  nic.at GmbH
Intended status: Standards Track                            M. Sabadello
Expires: February 7, 2019                               Danube Tech GmbH
                                                          August 6, 2018


             The Decentralized Identifier (DID) in the DNS
                       draft-mayrhofer-did-dns-00

Abstract

   This document specifies the use of the URI Resource Record Type to
   publish Decentralized Identifiers (DIDs) in the DNS.

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 https://datatracker.ietf.org/drafts/current/.

   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 February 7, 2019.

Copyright Notice

   Copyright (c) 2018 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
   (https://trustee.ietf.org/license-info) 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.




Mayrhofer, et al.       Expires February 7, 2019                [Page 1]


Internet-Draft           draft-mayrhofer-did-dns             August 2018


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  The '_did' Service Parameter for the URI RRType . . . . . . .   3
     3.1.  Owner Name  . . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  Weight, Priority  . . . . . . . . . . . . . . . . . . . .   4
   4.  Location of the Records . . . . . . . . . . . . . . . . . . .   4
     4.1.  Host Names  . . . . . . . . . . . . . . . . . . . . . . .   4
     4.2.  Email Addresses (Experimental)  . . . . . . . . . . . . .   4
   5.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   6.  Considered Alternatives . . . . . . . . . . . . . . . . . . .   4
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   10. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     10.1.  draft-mayrhofer-did-dns-00 . . . . . . . . . . . . . . .   5
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     11.1.  Normative References . . . . . . . . . . . . . . . . . .   5
     11.2.  Informative References . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Decentralized Identifiers (DIDs) [W3C-DID] use a Uniform Resource
   Identifier (URI) scheme [RFC3986] to identify persons, organizations,
   or things in decentralized infrastructure, such as blockchains and
   distributed ledgers.

   DIDs are structured around "methods", each method defining the syntax
   of the method specific identifier and the operations on the
   respective DIDs (See Section 3.2 of [W3C-DID] and [DID-METHODS]).
   For most methods, the method specific identifier content is not
   human-friendly (for example, hash values referring to transactions on
   a blockchain).  Most DIDs are therefore inherently hard to memorize
   for humans.

   By referring to DIDs from the DNS, those hard to memorize identifiers
   can be discovered via well known, human friendly and widely
   established names.  This document specifies such a protocol, and
   describes how DIDs can be discovered on the basis of host names and
   email addresses.

   Since DIDs use a URI scheme ('did'), this specification leverages the
   existing URI DNS Resource Record Type [RFC7553] for that purpose.
   However, the original specification of the URI RRType limits the
   possible values for the service parameters of the Owner name,
   effectively disallowing the DID use case described above.



Mayrhofer, et al.       Expires February 7, 2019                [Page 2]


Internet-Draft           draft-mayrhofer-did-dns             August 2018


   In order to allow inclusion of DIDs in the DNS, this document updates
   RFC7553 to allow the string '_did' as a service parameter in the
   Owner name of the URI RRType.  For a detailed discussion, see
   Section 3.

2.  Terminology

   "Owner name", "Priority", "Weight" and "Target" refer to the
   respective fields of the URI RRType, as specified in Section 4 of
   RFC7553.

   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.  The '_did' Service Parameter for the URI RRType

   As described in Section 1, RFC 7553 limits the set of strings allowed
   as service parameters in the Owner name of the URI RRType.  Valid
   strings have to be registered in either the "Service Name and
   Transport Protocol Port Number Registry" [RFC6335] or the
   "Enumservice Registrations" registry [RFC6117].  However, both
   registries are unsuitable for DIDs because:

   o  DIDs are not tied to a specific transport protocol, hence a
      registration in the Service Name registry is not possible (See
      Section 8.1.1. of RFC6335).

   o  Enumservice registrations apply to E.164 Number Mapping (ENUM)
      [RFC6116] only, while the use case for DIDs in the DNS extends
      beyond that limited scope.

3.1.  Owner Name

   Given the considerations above, it is believed that the most
   effective way to allow for DIDs in the URI RRType is extending the
   set of allowed service parameters used in the Owner name as follows:

   o  In addition to the choices listed in Section 4.1 of RFC7553, the
      service parameter of the Owner name in the URI RRType MAY be set
      to '_did' (without quotes).

   o  When '_did' is used as service parameter in a URI DNS record, the
      Target field MUST contain a URI of the 'did:' URI scheme.





Mayrhofer, et al.       Expires February 7, 2019                [Page 3]


Internet-Draft           draft-mayrhofer-did-dns             August 2018


3.2.  Weight, Priority

   The semantics of the Weight and Priority fields remain.  When a
   client encounters a DID method it does not support, it SHOULD
   consider the respective DID "unreachable" for the purpose of record
   selection, and proceed to the URI with the next-lowest-numbered
   Priority.  See Section 4.2 of RFC 7553.

4.  Location of the Records

4.1.  Host Names

   In order to discover the set of DIDs associated with a Host Name, a
   client prepends the given Host Name with the '_did' Service Parameter
   to create the Owner name, and then queries for the URI RRType set
   (RRSet) of the resulting Query Name.

4.2.  Email Addresses (Experimental)

   To discover DIDs associated with email addresses, the (experimental)
   model from DNS-Based Authentication of Named Entities (DANE) Bindings
   for OpenPGP [RFC7929] is used.  A client prepares the email address
   following the procedure outlined in Section 5 in RFC7929, except that
   the second left-most label in step 5 of that procedure MUST be set to
   '_did' instead.  Subsequently, the client performs a DNS query for
   the URI RRType (rather than the OPENPGPKEY RRType described in said
   section).

5.  Example

   The following example is a URI Resource Record which refers from the
   host name "example.net" to a Decentralized Identifier using the 'sov'
   method:

      _did.example.net.  IN URI 100 10 "did:sov:1234abcd"

6.  Considered Alternatives

   During the development of this document, the following alternatives
   were considered: A dedicated RRType, TXT records, an Enumservice,
   Well-Known URIs, direct registration in the Service Name Registry.
   Updating the URI specification was found to be the option with the
   highest likeliness of interoperability combined with the lowest
   impact on standardization and implementation.







Mayrhofer, et al.       Expires February 7, 2019                [Page 4]


Internet-Draft           draft-mayrhofer-did-dns             August 2018


7.  Acknowledgements

   Acknowledgements will be added here.

8.  IANA Considerations

   In order to prevent unintended name space collisions, IANA is
   requested to reserve the string 'did' (0x64 0x69 0x64) in the Service
   Name and Transport Protocol Port Number Registry.  The reason that a
   reservation (rather than an assignment) is requested is because
   according to Section 8.1.1. of RFC6335, a transport protocol is
   REQUIRED with such a registration.  However, DIDs are not related to
   a specific transport protocol, and so a reservation (if possible)
   seems to be the only way.

   Note that IANA has already created a provisional URI scheme
   registration for the 'did' scheme itself.

9.  Security Considerations

   Most of the considerations outlined in the base specification of the
   URI RRType (RFC7553) also apply to the DID use case - particularly
   the concerns around downgrade attacks when the record is not signed
   with the help of DNSSEC.  Note that the DID resolving process itself
   (out of scope of this document) can provide additional security
   information (such as a backreference to the DNS domain name).

10.  Changes

   [Note to RFC Editors: This whole section is to be removed before
   publication]

10.1.  draft-mayrhofer-did-dns-00

   Initial version

11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.







Mayrhofer, et al.       Expires February 7, 2019                [Page 5]


Internet-Draft           draft-mayrhofer-did-dns             August 2018


   [RFC7553]  Faltstrom, P. and O. Kolkman, "The Uniform Resource
              Identifier (URI) DNS Resource Record", RFC 7553,
              DOI 10.17487/RFC7553, June 2015,
              <https://www.rfc-editor.org/info/rfc7553>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [W3C-DID]  W3C, W3C., "Decentralized Identifiers (DIDs) v0.11", July
              2018, <https://w3c-ccg.github.io/did-spec/>.

11.2.  Informative References

   [DID-METHODS]
              W3C, W3C., "DID Method Registry", June 2018,
              <https://w3c-ccg.github.io/did-method-registry/>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <https://www.rfc-editor.org/info/rfc3986>.

   [RFC6116]  Bradner, S., Conroy, L., and K. Fujiwara, "The E.164 to
              Uniform Resource Identifiers (URI) Dynamic Delegation
              Discovery System (DDDS) Application (ENUM)", RFC 6116,
              DOI 10.17487/RFC6116, March 2011,
              <https://www.rfc-editor.org/info/rfc6116>.

   [RFC6117]  Hoeneisen, B., Mayrhofer, A., and J. Livingood, "IANA
              Registration of Enumservices: Guide, Template, and IANA
              Considerations", RFC 6117, DOI 10.17487/RFC6117, March
              2011, <https://www.rfc-editor.org/info/rfc6117>.

   [RFC6335]  Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
              Cheshire, "Internet Assigned Numbers Authority (IANA)
              Procedures for the Management of the Service Name and
              Transport Protocol Port Number Registry", BCP 165,
              RFC 6335, DOI 10.17487/RFC6335, August 2011,
              <https://www.rfc-editor.org/info/rfc6335>.

   [RFC7929]  Wouters, P., "DNS-Based Authentication of Named Entities
              (DANE) Bindings for OpenPGP", RFC 7929,
              DOI 10.17487/RFC7929, August 2016,
              <https://www.rfc-editor.org/info/rfc7929>.






Mayrhofer, et al.       Expires February 7, 2019                [Page 6]


Internet-Draft           draft-mayrhofer-did-dns             August 2018


Authors' Addresses

   Alexander Mayrhofer
   nic.at GmbH
   Karlsplatz 1/2/9
   Vienna  1010
   Austria

   Email: alex.mayrhofer.ietf@gmail.com


   Dimitrij Klesev
   nic.at GmbH
   Karlsplatz 1/2/9
   Vienna  1010
   Austria

   Email: dimitrij.klesev@nic.at


   Markus Sabadello
   Danube Tech GmbH
   Annagasse 8/1/8
   Vienna  1010
   Austria

   Email: markus@danubetech.com
























Mayrhofer, et al.       Expires February 7, 2019                [Page 7]


Html markup produced by rfcmarkup 1.129c, available from https://tools.ietf.org/tools/rfcmarkup/