DNS-SD Privacy Scaling Tradeoffs
draft-huitema-dnssd-privacyscaling-01

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Last updated 2018-07-03 (latest revision 2018-06-30)
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Network Working Group                                         C. Huitema
Internet-Draft                                      Private Octopus Inc.
Intended status: Informational                             June 29, 2018
Expires: December 31, 2018

                    DNS-SD Privacy Scaling Tradeoffs
                 draft-huitema-dnssd-privacyscaling-01

Abstract

   DNS-SD (DNS Service Discovery) normally discloses information about
   both the devices offering services and the devices requesting
   services.  This information includes host names, network parameters,
   and possibly a further description of the corresponding service
   instance.  Especially when mobile devices engage in DNS Service
   Discovery over Multicast DNS at a public hotspot, a serious privacy
   problem arises.

   The draft currently progressing in the DNS-SD Working Group assumes
   peer-to-peer pairing between the service to be discovered and each of
   its clients.  This has good security properties, but creates scaling
   issues, because each server needs to publish as many announcements as
   it has paired clients.  This leads to large number of operations when
   servers are paired with many clients.

   Different designs are possible.  For example, if there was only one
   server "discovery key" known by each authorized client, each server
   would only have to announce a single record, and clients would only
   have to process one response for each server that is present on the
   network.  Yet, these designs will present different privacy profiles,
   and pose different management challenges.  This draft analyses the
   tradeoffs between privacy and scaling in a set of different designs,
   using either shared secrets or public keys.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any

Huitema                 Expires December 31, 2018               [Page 1]
Internet-Draft      DNS-SD Privacy Scaling Tradeoffs           June 2018

   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 31, 2018.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Privacy and Secrets . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Pairing secrets . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Group public keys . . . . . . . . . . . . . . . . . . . .   4
     2.3.  Shared symmetric secret . . . . . . . . . . . . . . . . .   4
     2.4.  Shared public key . . . . . . . . . . . . . . . . . . . .   4
   3.  Scaling properties of different solutions . . . . . . . . . .   5
   4.  Comparing privacy posture of different solutions  . . . . . .   7
     4.1.  Effects of compromized client . . . . . . . . . . . . . .   7
     4.2.  Revocation  . . . . . . . . . . . . . . . . . . . . . . .   8
     4.3.  Effect of compromized server  . . . . . . . . . . . . . .   9
   5.  Summary of tradeoffs  . . . . . . . . . . . . . . . . . . . .   9
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  10
   9.  Informative References  . . . . . . . . . . . . . . . . . . .  10
   Appendix A.  Survey of Implementations  . . . . . . . . . . . . .  11
     A.1.  DNS-SD Privacy Extensions . . . . . . . . . . . . . . . .  11
     A.2.  Private IoT . . . . . . . . . . . . . . . . . . . . . . .  12
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   DNS-SD [RFC6763] over mDNS [RFC6762] enables configurationless
   service discovery in local networks.  It is very convenient for
   users, but it requires the public exposure of the offering and
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