Network Working Group E. Nordmark
Internet-Draft Zededa
Intended status: Standards Track July 2, 2018
Expires: January 3, 2019
Privacy issues in ID/locator separation systems
draft-nordmark-id-loc-privacy-00
Abstract
There exists several protocols and proposals for identifier/locator
split which have some form of control plane by which participating
nodes can use to share their current id to locator information with
their peers. This document explores some of the privacy
considerations for such a system.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Keywords and Terminology . . . . . . . . . . . . . . . . . . 3
3. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Threats against Privacy . . . . . . . . . . . . . . . . . . . 4
4.1. Location Privacy . . . . . . . . . . . . . . . . . . . . 4
4.2. Movement Privacy . . . . . . . . . . . . . . . . . . . . 4
5. Not everybody all the time . . . . . . . . . . . . . . . . . 4
5.1. Optimized routing . . . . . . . . . . . . . . . . . . . . 4
5.2. Family and Friends . . . . . . . . . . . . . . . . . . . 5
5.3. Business Assets . . . . . . . . . . . . . . . . . . . . . 5
6. Boundary between ID/locator part and rest of Internet . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
9. Normative References . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
When the IP address is separated, one way or another, into an
identifier and a locator there is typically a need to be able to look
up an identifier to find possible locators which can be used to reach
the identified endpoint. If such a system (think distributed
database) was publicly available while identifiers are assigned to
devices such as mobile phones which have a strong binding with an
individual, then this would introduce additional privacy
considerations which do not exist in the absence of the ID/locator
split.
Without an ID/locator split a device is already providing its IP
address (in the form of a source address) to any network device along
the path, and also to the remote endpoint. That endpoint in
particular might use IP geolocation databases to get a pretty good
idea of where its peer is located, for instance to offer information
and/or advertising relevant to that location.
However, such such a device (e.g., a laptop or smartphone connected
over WiFi) move e.g., from home to a coffee shop, the IP address
changes. This makes it harder for network devices along the paths to
realize that the its is the same mobile device. And if the mobile
device is not retaining cookies or logged into websites, those remote
peers would also have some difficulty determining it is the same
mobile device. Furthermore, a mobile device which is using typical
cellular network technologies end up with an IP address, at least as
seen by remote peers outside of the cellular network, which is
associated with the cellular operator but does not necessarily
indicate a particular location of the mobile device.
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Note that even if the IP address isn't always useful to track a
mobile device today, there are several mechanisms higher in the stack
which can do this. For instance cookies or SSL sessions,
applications which share GPS location, or operators who offer
additional location information (for instance based on which cellular
base station a mobile device is using) to business partners.
With that baseline in mind, let's look at what additional privacy
considerations can be introduced by a system which provides ID to
locator mappings.
2. Keywords and Terminology
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
document, are to be interpreted as described in [RFC2119].
3. Assumptions
We assume that there are benefits associated with sharing ID to
locator mappings with some peers sometimes. Those benefits can be
o Lower latency and higher bandwidth: If two peer devices have some
locators which are topologically closer, then sharing all the
locators means that the devices can find a short path (fewer hops
and/or shorter round-trip time), or find a path which offer higher
throughput, then if the devices only shared some form of default
locator.
o Higher availability and robustness: If two peer devices share all
their locators, then if there is some network outage the devices
can autonomously discover a working path using the different
locator pairs.
However, those benefits do not imply that it is a good idea to always
share all of the locators with everybody. That would make tracking
by third parties trivial.
A device can obfuscate itself by, instead of using a single long-
lived identifier, using multiple short-lived identifiers. In that
case the value to the ID/locator binding for any particular
identifier would be lower. However, this assumes that the device can
ensure unlinkablity between the different identifiers it is using
either concurrently or over time. Also, some of the benefits above
implicitly assume that there can be some long-lived sessions or
associations between pairs of identifiers. For instance, if a device
would need to go fetch the current identifier of its peer from some
remove system, then it might not experience improved robustness since
that fetch might depend on the failed external connectivity. Thus we
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believe that we can explore the core of the ID/locator privacy issue
by looking at long-lived identifiers.
4. Threats against Privacy
This is the first version of this draft so this is very preliminary.
But there seems to be at least two different privacy threats relating
to ID/locator mapping systems.
4.1. Location Privacy
If a third party can at any time determine the IP location of some
identifier, then the device can at one point be IP geolocated at
home, and later a coffee shop.
4.2. Movement Privacy
If a third party can determine that an identifier has changed
locator(s) at time T, then even without knowing the particular
locators before and after, it can correlate this movement event with
other information (e.g., security cameras) to create a binding
between the identifier and a person.
5. Not everybody all the time
In order to see the benefits about but minimizing the privacy
implication one can explore limiting to which peers and when the ID/
locator binding are exposed.
A few initial examples help illustrate this.
5.1. Optimized routing
If some operator of a network where there is a large amount of
mobility wants to ensure efficient routing, then a ID/locator split
approach might make sense. Such a system can potentially be limited
to the set of devices (routers etc) which are under the operators
control. If this is the case, then the ID/locator mapping system can
provide access control so that only those trusted devices can access
the mappings.
Note that from a privacy perspective this isn't any different than
the same operator using a link-state routing protocol to share host
routes for all the mobile devices. In that case all participants in
the link-state protocol can determine the location (attached to which
router) and notice any mobility events. Of course, there are
significant non-privacy differences between those two approaches.
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Exposing the ID/locator mapping to attached devices (e.g., any mobile
devices which wouldn't be trusted to participate in the link-state
routing counterpart approach), will change the privacy implications.
5.2. Family and Friends
There are cases where it is quite reasonable to share location
information with other family members or friends. For instance,
young children might run applications which enable their parents to
track them on their way to/from school. And I might share my
location with friends so we can more easily find each other while out
on town.
Today such location sharing happens at an application layer using GPS
coordinates. But while such sharing is in effect, it wouldn't be
unreasonable to also consider sharing IP locators to make it more
efficient or more robust to e.g., route a video feed from one device
to another.
5.3. Business Assets
In the area of Industrial IoT there are cases where an asset owner
might want to ensure that their assets can communicate efficiently
and robustly. In many cases those assets might be decoupled from any
persons, but there can still be strong reasons to not share the ID/
locator binding with third parties, such as enabling competitors to
determine the number of deployed devices in a particular IP prefix.
6. Boundary between ID/locator part and rest of Internet
If the access to the ID/locator mapping are restricted as suggested
above, then most of the potential peer devices would not have access
to the ID/locator mappings. This means that there has to be a
demarcation point between the part of the network which can access
the ID/locator mappings for a particular identifier and the one which
can not. There might be several choices how to handle this such as
still using an ID/locator system but pointing a locator for some
fixed anchor point, or injecting routing prefixes for the ID prefixes
into the normal routing system, or not providing any stable locators
across this boundary; only allow ephemeral IP addresses per session
or otherwise limited exposure.
7. Security Considerations
This document discusses privacy considerations, but does not explore
any security considerations.
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8. IANA Considerations
There are no IANA actions needed for this document.
9. 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>.
Author's Address
Erik Nordmark
Zededa
Santa Clara, CA
USA
Email: nordmark@sonic.net
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