Privacy Extensions for DNS-SD
draft-huitema-dnssd-privacy-01

The information below is for an old version of the document
Document Type Active Internet-Draft (candidate for dnssd WG)
Authors Christian Huitema  , Daniel Kaiser 
Last updated 2016-07-25 (latest revision 2016-06-10)
Replaced by draft-ietf-dnssd-privacy
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Intended RFC status Proposed Standard
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Network Working Group                                         C. Huitema
Internet-Draft                                                 Microsoft
Intended status: Standards Track                               D. Kaiser
Expires: December 12, 2016                        University of Konstanz
                                                           June 10, 2016

                     Privacy Extensions for DNS-SD
                   draft-huitema-dnssd-privacy-01.txt

Abstract

   DNS-SD allows discovery of services published in DNS or MDNS.  The
   publication normally discloses information about the device
   publishing the services.  There are use cases where devices want to
   communicate without disclosing their identity, for example two mobile
   devices visiting the same hotspot.

   We propose to solve this problem by a two-stage approach.  In the
   first stage, hosts discover Private Discovery Service Instances via
   DNS-SD using special formats to protect their privacy.  These service
   instances correspond to Private Discovery Servers running on peers.
   In the second stage, hosts directly query these Private Discovery
   Servers via DNS-SD over TLS.  A pairwise shared secret necessary to
   establish these connections is only known to hosts authorized by a
   pairing system.

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 http://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 December 12, 2016.

Huitema & Kaiser        Expires December 12, 2016               [Page 1]

Internet-Draft          DNS-SD Privacy Extensions              June 2016

Copyright Notice

   Copyright (c) 2016 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
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements  . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Privacy Implications of DNS-SD  . . . . . . . . . . . . . . .   4
     2.1.  Privacy Implication of Publishing Service Instance Names    4
     2.2.  Privacy Implication of Publishing Node Names  . . . . . .   5
     2.3.  Privacy Implication of Publishing Service Attributes  . .   5
     2.4.  Device Fingerprinting . . . . . . . . . . . . . . . . . .   6
     2.5.  Privacy Implication of Discovering Services . . . . . . .   6
   3.  Limits of a Simple Design . . . . . . . . . . . . . . . . . .   7
     3.1.  Obfuscated Instance Names . . . . . . . . . . . . . . . .   7
     3.2.  Names of Obfuscated Services  . . . . . . . . . . . . . .   8
     3.3.  Scaling Issues with Obfuscation . . . . . . . . . . . . .  10
   4.  Design of the Private DNS-SD Discovery Service  . . . . . . .  11
     4.1.  Device Pairing  . . . . . . . . . . . . . . . . . . . . .  11
       4.1.1.  Shared Secret . . . . . . . . . . . . . . . . . . . .  12
       4.1.2.  Secure Authenticated Pairing Channel  . . . . . . . .  12
       4.1.3.  Public Authentication Keys  . . . . . . . . . . . . .  12
     4.2.  Discovery of the Private Discovery Service  . . . . . . .  13
     4.3.  Private Discovery Service . . . . . . . . . . . . . . . .  14
       4.3.1.  A Note on Private DNS Services  . . . . . . . . . . .  15
     4.4.  Randomized Host Names . . . . . . . . . . . . . . . . . .  16
     4.5.  Timing of Obfuscation and Randomization . . . . . . . . .  16
   5.  Private Discovery Service Specification . . . . . . . . . . .  16
     5.1.  Host Name Randomization . . . . . . . . . . . . . . . . .  17
     5.2.  Device Pairing  . . . . . . . . . . . . . . . . . . . . .  17
     5.3.  Private Discovery Server  . . . . . . . . . . . . . . . .  18
       5.3.1.  Establishing TLS Connections  . . . . . . . . . . . .  18
     5.4.  Publishing Private Discovery Service Instances  . . . . .  19
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