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Nordmark 3 Internet-Draft Zededa 4 Intended status: Standards Track July 2, 2018 5 Expires: January 3, 2019 7 Privacy issues in ID/locator separation systems 8 draft-nordmark-id-loc-privacy-00 10 Abstract 12 There exists several protocols and proposals for identifier/locator 13 split which have some form of control plane by which participating 14 nodes can use to share their current id to locator information with 15 their peers. This document explores some of the privacy 16 considerations for such a system. 18 Status of This Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at http://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on January 3, 2019. 35 Copyright Notice 37 Copyright (c) 2018 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (http://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 Table of Contents 52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 53 2. Keywords and Terminology . . . . . . . . . . . . . . . . . . 3 54 3. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 3 55 4. Threats against Privacy . . . . . . . . . . . . . . . . . . . 4 56 4.1. Location Privacy . . . . . . . . . . . . . . . . . . . . 4 57 4.2. Movement Privacy . . . . . . . . . . . . . . . . . . . . 4 58 5. Not everybody all the time . . . . . . . . . . . . . . . . . 4 59 5.1. Optimized routing . . . . . . . . . . . . . . . . . . . . 4 60 5.2. Family and Friends . . . . . . . . . . . . . . . . . . . 5 61 5.3. Business Assets . . . . . . . . . . . . . . . . . . . . . 5 62 6. Boundary between ID/locator part and rest of Internet . . . . 5 63 7. Security Considerations . . . . . . . . . . . . . . . . . . . 5 64 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 65 9. Normative References . . . . . . . . . . . . . . . . . . . . 6 66 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 68 1. Introduction 70 When the IP address is separated, one way or another, into an 71 identifier and a locator there is typically a need to be able to look 72 up an identifier to find possible locators which can be used to reach 73 the identified endpoint. If such a system (think distributed 74 database) was publicly available while identifiers are assigned to 75 devices such as mobile phones which have a strong binding with an 76 individual, then this would introduce additional privacy 77 considerations which do not exist in the absence of the ID/locator 78 split. 80 Without an ID/locator split a device is already providing its IP 81 address (in the form of a source address) to any network device along 82 the path, and also to the remote endpoint. That endpoint in 83 particular might use IP geolocation databases to get a pretty good 84 idea of where its peer is located, for instance to offer information 85 and/or advertising relevant to that location. 87 However, such such a device (e.g., a laptop or smartphone connected 88 over WiFi) move e.g., from home to a coffee shop, the IP address 89 changes. This makes it harder for network devices along the paths to 90 realize that the its is the same mobile device. And if the mobile 91 device is not retaining cookies or logged into websites, those remote 92 peers would also have some difficulty determining it is the same 93 mobile device. Furthermore, a mobile device which is using typical 94 cellular network technologies end up with an IP address, at least as 95 seen by remote peers outside of the cellular network, which is 96 associated with the cellular operator but does not necessarily 97 indicate a particular location of the mobile device. 99 Note that even if the IP address isn't always useful to track a 100 mobile device today, there are several mechanisms higher in the stack 101 which can do this. For instance cookies or SSL sessions, 102 applications which share GPS location, or operators who offer 103 additional location information (for instance based on which cellular 104 base station a mobile device is using) to business partners. 106 With that baseline in mind, let's look at what additional privacy 107 considerations can be introduced by a system which provides ID to 108 locator mappings. 110 2. Keywords and Terminology 112 The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, 113 SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this 114 document, are to be interpreted as described in [RFC2119]. 116 3. Assumptions 118 We assume that there are benefits associated with sharing ID to 119 locator mappings with some peers sometimes. Those benefits can be 121 o Lower latency and higher bandwidth: If two peer devices have some 122 locators which are topologically closer, then sharing all the 123 locators means that the devices can find a short path (fewer hops 124 and/or shorter round-trip time), or find a path which offer higher 125 throughput, then if the devices only shared some form of default 126 locator. 127 o Higher availability and robustness: If two peer devices share all 128 their locators, then if there is some network outage the devices 129 can autonomously discover a working path using the different 130 locator pairs. 132 However, those benefits do not imply that it is a good idea to always 133 share all of the locators with everybody. That would make tracking 134 by third parties trivial. 136 A device can obfuscate itself by, instead of using a single long- 137 lived identifier, using multiple short-lived identifiers. In that 138 case the value to the ID/locator binding for any particular 139 identifier would be lower. However, this assumes that the device can 140 ensure unlinkablity between the different identifiers it is using 141 either concurrently or over time. Also, some of the benefits above 142 implicitly assume that there can be some long-lived sessions or 143 associations between pairs of identifiers. For instance, if a device 144 would need to go fetch the current identifier of its peer from some 145 remove system, then it might not experience improved robustness since 146 that fetch might depend on the failed external connectivity. Thus we 147 believe that we can explore the core of the ID/locator privacy issue 148 by looking at long-lived identifiers. 150 4. Threats against Privacy 152 This is the first version of this draft so this is very preliminary. 153 But there seems to be at least two different privacy threats relating 154 to ID/locator mapping systems. 156 4.1. Location Privacy 158 If a third party can at any time determine the IP location of some 159 identifier, then the device can at one point be IP geolocated at 160 home, and later a coffee shop. 162 4.2. Movement Privacy 164 If a third party can determine that an identifier has changed 165 locator(s) at time T, then even without knowing the particular 166 locators before and after, it can correlate this movement event with 167 other information (e.g., security cameras) to create a binding 168 between the identifier and a person. 170 5. Not everybody all the time 172 In order to see the benefits about but minimizing the privacy 173 implication one can explore limiting to which peers and when the ID/ 174 locator binding are exposed. 176 A few initial examples help illustrate this. 178 5.1. Optimized routing 180 If some operator of a network where there is a large amount of 181 mobility wants to ensure efficient routing, then a ID/locator split 182 approach might make sense. Such a system can potentially be limited 183 to the set of devices (routers etc) which are under the operators 184 control. If this is the case, then the ID/locator mapping system can 185 provide access control so that only those trusted devices can access 186 the mappings. 188 Note that from a privacy perspective this isn't any different than 189 the same operator using a link-state routing protocol to share host 190 routes for all the mobile devices. In that case all participants in 191 the link-state protocol can determine the location (attached to which 192 router) and notice any mobility events. Of course, there are 193 significant non-privacy differences between those two approaches. 195 Exposing the ID/locator mapping to attached devices (e.g., any mobile 196 devices which wouldn't be trusted to participate in the link-state 197 routing counterpart approach), will change the privacy implications. 199 5.2. Family and Friends 201 There are cases where it is quite reasonable to share location 202 information with other family members or friends. For instance, 203 young children might run applications which enable their parents to 204 track them on their way to/from school. And I might share my 205 location with friends so we can more easily find each other while out 206 on town. 208 Today such location sharing happens at an application layer using GPS 209 coordinates. But while such sharing is in effect, it wouldn't be 210 unreasonable to also consider sharing IP locators to make it more 211 efficient or more robust to e.g., route a video feed from one device 212 to another. 214 5.3. Business Assets 216 In the area of Industrial IoT there are cases where an asset owner 217 might want to ensure that their assets can communicate efficiently 218 and robustly. In many cases those assets might be decoupled from any 219 persons, but there can still be strong reasons to not share the ID/ 220 locator binding with third parties, such as enabling competitors to 221 determine the number of deployed devices in a particular IP prefix. 223 6. Boundary between ID/locator part and rest of Internet 225 If the access to the ID/locator mapping are restricted as suggested 226 above, then most of the potential peer devices would not have access 227 to the ID/locator mappings. This means that there has to be a 228 demarcation point between the part of the network which can access 229 the ID/locator mappings for a particular identifier and the one which 230 can not. There might be several choices how to handle this such as 231 still using an ID/locator system but pointing a locator for some 232 fixed anchor point, or injecting routing prefixes for the ID prefixes 233 into the normal routing system, or not providing any stable locators 234 across this boundary; only allow ephemeral IP addresses per session 235 or otherwise limited exposure. 237 7. Security Considerations 239 This document discusses privacy considerations, but does not explore 240 any security considerations. 242 8. IANA Considerations 244 There are no IANA actions needed for this document. 246 9. Normative References 248 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 249 Requirement Levels", BCP 14, RFC 2119, 250 DOI 10.17487/RFC2119, March 1997, . 253 Author's Address 255 Erik Nordmark 256 Zededa 257 Santa Clara, CA 258 USA 260 Email: nordmark@sonic.net