Internet DRAFT - draft-irtf-hrpc-anonymity
draft-irtf-hrpc-anonymity
Human Rights Protocol Considerations Research Group S. Bortzmeyer
Internet-Draft AFNIC
Intended status: Informational N. ten Oever
Expires: August 27, 2018 University of Amsterdam
February 23, 2018
Anonymity, Human Rights and Internet Protocols
draft-irtf-hrpc-anonymity-00
Abstract
Anonymity is less discussed in the IETF than for instance security
[RFC3552] or privacy [RFC6973]. This can be attributed to the fact
anonymity is a hard technical problem or that anonymizing user data
is not of specific market interest. It remains a fact that 'most
internet users would like to be anonymous online at least
occasionally' [Pew].
This document aims to break down the different meanings and
implications of anonymity on a mediated computer network.
Status of This Memo
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Vocabulary Used . . . . . . . . . . . . . . . . . . . . . . . 3
3. Should protocols promote anonymity? . . . . . . . . . . . . . 4
4. Example of use cases . . . . . . . . . . . . . . . . . . . . 5
4.1. Simultaneous use . . . . . . . . . . . . . . . . . . . . 5
4.2. Successive use . . . . . . . . . . . . . . . . . . . . . 5
4.3. Selective use . . . . . . . . . . . . . . . . . . . . . . 6
4.4. User analysis . . . . . . . . . . . . . . . . . . . . . . 6
5. Practical advices . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Protocol developers . . . . . . . . . . . . . . . . . . . 6
5.2. Protocol implementors . . . . . . . . . . . . . . . . . . 7
6. Open Questions . . . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
9. Research Group Information . . . . . . . . . . . . . . . . . 8
10. Objections against anonymity . . . . . . . . . . . . . . . . 8
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
11.1. Informative References . . . . . . . . . . . . . . . . . 8
11.2. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
There seems to be a clear need for anonymity online in an environment
where harassment on the Internet is on the increase [Pew2] and the UN
Special Rapporteur for Freedom of Expression calls anonymity
'necessary for the exercise of the right to freedom of opinion and
expression in the digital age' [UNHRC2015].
Nonetheless anonymity is not getting much discussion at the IETF,
providing anonymity does not seem a (semi-)objective for many
protocols, even though several documents contribute to improving
anonymity such as [RFC7258], [RFC7626], [RFC7858].
There are initiatives on the Internet to improve end users anonymity,
most notably [torproject], but these initiatives rely on adding
encryption in the application layer.
This document aims to break down the different meanings and
implications of anonymity on a mediated computer network and to see
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whether (some parts of) anonymity should be taken into consideration
in protocol development.
2. Vocabulary Used
Concepts in this draft currently strongly hinges on [AnonTerm]
Anonymity A state of an individual in which an observer or attacker
cannot identify the individual within a set of other individuals
(the anonymity set). [RFC6973]
Linkability Linkability of two or more items of interest (IOIs -
Items Of Interest, e.g., subjects, messages, actions, ...) from an
attacker's perspective means that within the system (comprising
these and possibly other items), the attacker can sufficiently
distinguish whether these IOIs are related or not. [AnonTerm]
Official identity Government-issued identity, as written on ID cards
and passports. We don't use terms like "real names" since a
choosen pseudonym, for instance, is not less real than a identity
given at birth.
Pseudonymity Derived from pseudonym, a persistent identity which is
not the same as the entity's given (or official) name. For all
IETF protocols, pseudonimity is a given: protocols don't care
whether the identity is an official one or not. Even if the
protocol allows to use official identities (for instance in the
From: header of an Internet email), it does not require it. But
it should be noted that, if the user cannot create new pseudonyms
easily, pseudonyms suffer from linkability. Unlinkability depends
on this ability to create new pseudonyms gratis and at will (good
examples are SSH keys or Bitcoin addresses). Easy creation will
allow to have one pseudonym per use, thus defeating linkability.
Unlinkability Unlinkability of two or more items of interest (IOIs,
e.g., subjects, messages, actions, ...) from an attacker's
perspective means that within the system (comprising these and
possibly other items), the attacker cannot sufficiently
distinguish whether these IOIs are related or not. [AnonTerm]
Undetectability The impossibility of being noticed or discovered
Undetectability of an item of interest (IOI) from an attacker's
perspective means that the attacker cannot sufficiently
distinguish whether it exists or not [AnonTerm]
Unobservability
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Unobservability of an item of interest (IOI) means:
undetectability of the IOI against all subjects uninvolved in it
and
anonymity of the subject(s) involved in the IOI even against the
other subject(s) involved in that IOI. [AnonTerm]
It should be noted that the word "anonymity" is both very loaded
politically (witness all the headlines about the "darknet") and
poorly understood. Most texts talking about anonymity actually refer
to pseudonymity (for instance, when people say that "Bitcoin is
anonymous"). This confusion is even in the example given in
[RFC4949] definition of anonymity.
Anonymity is strongly linked to unlinkability: if your actions are
linkable, it suffices that one of them is tied to your identity, and
anonymity is over.
It should be noted that anonymity is not binary: there have been
these recent years a lot of progress of desanonymisation techniques
(see also [GDPR], article 26). Data is never fully "anonymous", it
is only more or less anonymous. [RFC6235] [MITdeano] [Utexas]
[Article29]
3. Should protocols promote anonymity?
The amount of data that is generated by and about individuals is
growing exponentially. This can be attributed to the fact that an
ever increasing number of actions is digitally mediated, and the
increase of connected sensors in the every day environment. Even
though these two causes do not fully fall within the scope of the
IETF, there is a significant part of these two examples that do.
TODO add here more examples of the need to anonymity
With the increase of data there is also an increasing ability for
third parties to analyze human behaviour. It should be noted that
any data that could identify an individual is personally identifiable
information (PII). This means that information which can be used to
distinguish an indivual from other individuals can be considered as
personally identiable information. The access and control of
personally identifiable information by a third party is a (potential)
liability for both the third party and the individual. This
liability could for example translate into a physical risk for the
individual or into a legal risk for the third party under information
security and privacy laws.
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Some network operators argue that without the opportunity to
persistently identify individual users it becomes harder to thwart
attacks and troubleshoot network issues. Whereas identification
might be helpful to address issues in some cases, it poses an
inherent threat to the anonymity of users. Not protecting the
anonymity of users leads to a deterioration of the right to privacy,
and the right to freedom of opinion and expression. There can be
limitations the right to privacy and freedom of expression, but these
should always be provided by law and necessary and proportionate to
achieve one of a handful of legitimate objectives. It is clear that
anonymity may make system and network administration different. To
quote [RFC7824], "Those properties (stable and trackable IP
addresses, derived from static identifiers) are convenient for system
administrators". Here, there is a clear and fundamental tussle
between the protection of the users and the ability of the system and
network administrator to continue their work in the same way.
Anonymity will always be a balancing act between user protection
(which requires a high level of anonymity) and other requirments for
operations and research, such as routing information. Anonymity is
by no means achieved by default in an online environment, nor has it
been a strong consideration in protocol development in the
development of the Internet. Increasing anonymity in the digital
environment is not an easy task, exactly because the ubiquity of data
that is generated and stored. But exactly the fact that we generate
so much data urges us to address this issue.
4. Example of use cases
4.1. Simultaneous use
One user may use concurrently several identities, mixing them in
operations, while wanting to keep them distinct. The protocol and
its implementations should not preclude this use.
4.2. Successive use
One user may switch from one identity to another. In that case, it
must be doable without a "bleedover" from the old identity to the new
one.
One of the reasons to switch identities might be to make the
relationship between this identity and another one (for instance the
official one) more difficult. The longer you use a pseudonym, the
more clues you give to someone who tries to unveil pseudonymity.
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4.3. Selective use
A user might want to retain their anonymity to certain actors /
protocols, but identified to others. Also, she may also wish to be
identified for some operations but not always.
4.4. User analysis
A user might want to understand which other actors might
(potentially) have which level of information about them. This
conflicts of course with privacy because the user has to reveal who
he is. Example: if a domain name registry does not publish the name
of a registrant, the registrant cannot check if the person who did
the registration indicated the name of their client, or their own
name.
5. Practical advices
5.1. Protocol developers
First, the protocol should avoid to have mandatory persistent
identifiers.
Even without persistent identifiers, anonymity could be broken by
examining the patterns of access. If an user visits each morning the
three same Web sites, always in the same order, it will be easy to
identify them even without persistent identifier. Protocol designers
should therefore ask themselves if patterns are easily visible, or
obfuscated in some way.
If the protocol collects data and distributes it (see [RFC6235]),
"anonymizing" the data is often suggested but it is notoriously hard.
Do not think that just dropping the last byte of an IP address
"anonymizes" data.
Pay attention to the fact that Internet actors do not all see the
same thing. Consider the anonymity of the user with respect to:
- local network operator
- other networks you connect to
- your communications peer on the other end of the pipe
- intermediaries ([RFC6973])
- enablers ([RFC6973])
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- someone who is in several roles, for instance a big state
surveillance agency
5.2. Protocol implementors
Avoid adding options or configurations that create or might lead to
patterns or regularities that are not explicitely required by the
protocol.
An example is DHCP where sending a persistent identifier as the
client name was not mandatory but, in practice, done by many
implementations, before [RFC7844].
If an implementation allows for identity management, there should be
a clear barrier between the identities to ensure that they cannot
(easily) be associated with each other.
If there are anonymization option for the protocol, these should be
enabled by default.
6. Open Questions
While analyzing protocols for their impact on users anonymity, would
it make sense to ask the following questions:
1. How does the protocol impact pseudonymity? If the protocol
limits the creation of new pseudonyms, it can limit their
usefulness to "hide" an user's identity. For instance, IP
addresses are pseudonyms but, since they are not under end
users's control, they have strong linkability. That's why they
are rightly regarded as personal identifiers [EUcourt]. On the
other hand, Bitcoin addresses are pseudonyms with limited
linkability, since the user can always create a lot of them.
2. Could there be more advice for protocol developers and
implementers to improve anonymity? (Besides the ones in
Section 5.)
7. Security Considerations
As this draft concerns a research document, there are no security
considerations.
8. IANA Considerations
This document has no actions for IANA.
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9. Research Group Information
The discussion list for the IRTF Human Rights Protocol Considerations
proposed working group is located at the e-mail address hrpc@ietf.org
[1]. Information on the group and information on how to subscribe to
the list is at https://www.irtf.org/mailman/listinfo/hrpc [2]
Archives of the list can be found at: https://www.irtf.org/mail-
archive/web/hrpc/current/index.html [3]
10. Objections against anonymity
TODO: should be turned into an appendix. This draft is about how to
allow anonymity, not about how to fight it.
For a long time, there have been objections against anonymity. This
document won't attempt to rebuke them all, since it is concerned
about how to ensure that protocols allow anonymity. But it is
interesting to keep in mind that protocols never forbid anonymity.
If smeones want his or her actions to be trackable, and under her or
his official name, they can do so, by adding this information to
their messages. In the same way, people are free not to engage with
anonymous entities, in the same way that a SIP use, for instance, is
free not to pick up a call if it comes from
sip:anonymous@anonymous.invalid. This document is concerned about
enabling anonymity, not about mandating it.
11. References
11.1. Informative References
[AnonTerm]
Pfitzmann, A. and M. Hansen, "A terminology for talking
about privacy by data minimization: Anonymity,
Unlinkability, Undetectability, Unobservability,
Pseudonymity, and Identity Management", 2010,
<http://dud.inf.tu-dresden.de/literatur/
Anon_Terminology_v0.34.pdf>.
[Article29]
Article29, ., "Opinion 05/2014 on Anonymisation
Techniques", 2014, <http://ec.europa.eu/justice/data-
protection/article-29/documentation/opinion-
recommendation/files/2014/wp216_en.pdf>.
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[EUcourt] "EUCJ Case C-70/10: Scarlet Extended SA vs. Societe belge
des auteurs, compositeurs et editeurs SCRL (SABAM)", 2011,
<http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CEL
EX:62010CJ0070:EN:HTML&lipi=urn%3Ali%3Apage%3Ad_flagship3_
pulse_read%3BSFHas%2FXMRHeHVu46775ezw%3D%3D>.
[GDPR] European Parliament and Council, ., "REGULATION (EU)
2016/679 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL on
the protection of natural persons with regard to the
processing of personal data and on the free movement of
such data, and repealing Directive 95/46/EC (General Data
Protection Regulation)", 2016, <http://eur-lex.europa.eu/
legal-content/EN/TXT/HTML/?uri=CELEX:32016R0679>.
[MITdeano]
de Montjoye, Y., Hidalgo, C., Verleysen, M., and V.
Blondel, "Unique in the Crowd: The privacy bounds of human
mobility", 2013,
<https://www.nature.com/articles/srep01376>.
[Pew] Rainie, L., Kiesler, S., Kang, R., and M. Madden,
"Anonymity, Privacy, and Security Online", 2013,
<http://www.pewinternet.org/2013/09/05/
anonymity-privacy-and-security-online/>.
[Pew2] Duggan, M., "Online Harassment", 2014,
<http://www.pewinternet.org/2014/10/22/
online-harassment/>.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552,
DOI 10.17487/RFC3552, July 2003,
<https://www.rfc-editor.org/info/rfc3552>.
[RFC4949] Shirey, R., "Internet Security Glossary, Version 2",
FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
<https://www.rfc-editor.org/info/rfc4949>.
[RFC6235] Boschi, E. and B. Trammell, "IP Flow Anonymization
Support", RFC 6235, DOI 10.17487/RFC6235, May 2011,
<https://www.rfc-editor.org/info/rfc6235>.
[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
Morris, J., Hansen, M., and R. Smith, "Privacy
Considerations for Internet Protocols", RFC 6973,
DOI 10.17487/RFC6973, July 2013,
<https://www.rfc-editor.org/info/rfc6973>.
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[RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
2014, <https://www.rfc-editor.org/info/rfc7258>.
[RFC7626] Bortzmeyer, S., "DNS Privacy Considerations", RFC 7626,
DOI 10.17487/RFC7626, August 2015,
<https://www.rfc-editor.org/info/rfc7626>.
[RFC7824] Krishnan, S., Mrugalski, T., and S. Jiang, "Privacy
Considerations for DHCPv6", RFC 7824,
DOI 10.17487/RFC7824, May 2016,
<https://www.rfc-editor.org/info/rfc7824>.
[RFC7844] Huitema, C., Mrugalski, T., and S. Krishnan, "Anonymity
Profiles for DHCP Clients", RFC 7844,
DOI 10.17487/RFC7844, May 2016,
<https://www.rfc-editor.org/info/rfc7844>.
[RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
and P. Hoffman, "Specification for DNS over Transport
Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May
2016, <https://www.rfc-editor.org/info/rfc7858>.
[torproject]
The Tor Project, ., "Tor Project - Anonymity Online",
2007, <https://www.torproject.org/>.
[UNHRC2015]
Kaye, D., "Anonymity, Privacy, and Security Online (A/
HRC/29/32)", 2015, <http://www.ohchr.org/EN/HRBodies/HRC/R
egularSessions/Session29/Documents/A.HRC.29.32_AEV.doc>.
[Utexas] Narayanan, A. and V. Shmatikov, "Robust De-anonymization
of Large Sparse Datasets", 2008,
<http://www.cs.utexas.edu/~shmat/shmat_oak08netflix.pd>.
11.2. URIs
[1] mailto:hrpc@ietf.org
[2] https://www.irtf.org/mailman/listinfo/hrpc
[3] https://www.irtf.org/mail-archive/web/hrpc/current/index.html
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Authors' Addresses
Stephane Bortzmeyer
AFNIC
EMail: bortzmeyer+ietf@nic.fr
Niels ten Oever
University of Amsterdam
EMail: mail@nielstenoever.net
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