Internet DRAFT - draft-cooper-ietf-privacy-requirements
draft-cooper-ietf-privacy-requirements
Network Working Group A. Cooper
Internet-Draft CDT
Intended status: Best Current Practice S. Farrell
Expires: April 24, 2014 Trinity College Dublin
S. Turner
IECA, Inc.
October 21, 2013
Privacy Requirements for IETF Protocols
draft-cooper-ietf-privacy-requirements-01.txt
Abstract
It is the consensus of the IETF that our protocols be designed to
avoid privacy violations to the extent possible. This document
establishes a number of protocol design choices as Best Current
Practices for the purpose of avoiding such violations.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 24, 2014.
Copyright Notice
Copyright (c) 2013 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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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 3
4. Examples and Explanation . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
8. Informative References . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
The IETF has long-standing principles that support strong security in
protocol design and a tradition of encouraging protocol designers to
take these principles into account. [RFC1984] articulated the view
that encryption is an important tool to protect the cofidentiality of
communications, and that as such it should be encouraged and
available to all. [RFC3365] requires that all protocols implement
strong security. [RFC3552] provides guidance about how to consider
security in protocol design and how to document security choices. In
[RFC2804], the IETF established a policy of not considering
wiretapping requirements in IETF standards-track protocols.
[RFC6973] explains the many different aspects of privacy that can be
affected by Internet protocol design and provides guidance to help
designers consider privacy in their work.
This document extends the existing body of IETF principles concerning
security by articulating Best Current Practices for avoiding privacy
violations and establishing support for privacy as a principle of
IETF protocol design. These principles, old and new, should be
applied when designing new protocols, and where applicable, should be
considered for updates of existing protocols.
It is also the consensus of the IETF that pervasive surveillance is
an attack on privacy that should be defended against through protocol
design.
Discussion of this draft is directed to the ietf-privacy@ietf.org
list.
2. Terminology
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119]. These words take their normative meanings only when they
are presented in ALL UPPERCASE.
"Opportunistic encryption" is defined as encryption without any pre-
arrangement specific to the pair of systems involved (e.g., by using
a Diffie-Hellman exchange). See [RFC4322].
Privacy-specific terminology is provided in [RFC6973]. Of particular
relevance to this document is the term "personal data," defined as
"any information relating to an individual who can be identified,
directly or indirectly." Identifiers such as IP addresses that can
remain consistent over time or that particular parties associate with
directly identifiable information (such as a real name or street
address) are therefore considered to be personal data.
3. Recommendations
There are inherent privacy risks with protocols that allow the
communicating parties to store personal data, transport personal
data, or are vulnerable to other parties observing the personal data
in the exchanged communications. Most Internet communications
involve such risks, which can allow entities to build large databases
of information that by themselves or in conjunction with other
databases can identify people and their actions in invasive ways.
Therefore, to the extent consistent with basic protocol operation and
management, standards-track IETF protocols that involve transmission
of personal data:
1. MUST minimize their use of such personal data, and
2. where personal data is sent, MUST have well-defined and
interoperable ways to send such data encrypted for the intended
recipient(s).
While existing principles call for strong security, it is important
to note that strong security only in cases where the other party can
be authenticated does not by itself solve all privacy problems. To
guard against dangers of large-scale privacy attacks, some protection
is needed also for other situations.
As a consequence, at minimum, opportunistic encryption MUST be well-
defined for new IETF standards track protocols. This requirement can
be waived only in exceptional circumstances where the protocol's
utility would be eliminated or severely diminished if opportunistic
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encryption were defined. Note that encryption provides one aspect of
privacy protection, namely confidentiality. In most cases it will be
better to (also) specify how to do one-sided (e.g., TLS server
authentication as commonly used in the web) or mutually authenticated
encryption. Where both opportunistic and one-sided or mutually
authenticated encryption are specified, protocols MUST also protect
against downgrade attacks so that scenarios where authentication is
required cannot easily be manipulated into using opportunistic
encryption which will often be subject to man-in-the-middle attacks.
Note that these encryption requirements are contingent on
practicality - if some personal data really has to be sent in clear
for a protocol to be able to operate, and even opportunistic
encryption is not possible, then a standards-track protocol that does
not define how to protect that data will be consistent with this BCP.
The IETF will have to decide in such cases whether standardising that
protocol benefits the Internet or not.
Many IETF protocols allow for some data items to be optionally or
conditionally sent. If personal data can be sent, then the
conditions above apply.
Specifications that do not meet the criteria above MUST include (or
reference) an explanation of why they do not conform to this BCP.
4. Examples and Explanation
This section has some examples and explanatory material. [[More,
including references, will be added as discussion evolves.]]
DHCP is an example of a protocol where it seems quite hard to provide
useful confidentiality. Should a new DHCP option be defined that
carries personal data, then the IETF would have to decide if the
benefit of that outweighs the potential privacy cost.
For some protocols, layering on top of a security protocol like TLS,
SSH or IPsec can be a useful way to provide confidentiality.
However, just because it could be possible to do that does not mean
that that is sufficient to claim conformance with this BCP. For
example, claiming that Diameter conformed to this BCP becuase one
could in principle run Diameter over IPsec would not be credible, as
it seems that such deployments are rare to non-existent. In the same
way that being being realistic is important when we consider a claim
that sending personal data is unavoidable, it is just as important
when claiming that layering on top of a security protocol can meet
the requirements of this BCP.
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For some protocols, minimizing the use of personal data involves
limiting the lifetime of identifiers. In cases where an identifier
refers to an individual (or a proxy for an individual, such as a host
device or software instance), the longer that identifier persists and
the more contexts in which it is used, the more it can facilitate
correlation and tracking of information related to the individual and
his or her activities. Creating identifiers that have limited
lifetimes by default reduces the possibility that multiple protocol
interactions or communications can be correlated back to the same
individual. [RFC4941] provides an example in the case of stateless
autoconfiguration of IPv6 interface identifiers.
Since the goal here is to have a BCP that covers all IETF standards
track protocols we clearly cannot address all aspects of privacy, for
example user participation, since that would only be relevant for a
small proportion of IETF protocols.
One could consider mininimising the personal data sent by IETF
protocols as a form being conservative in what you send, one of the
longest standing principles in IETF protocol design. There doesn't
seem to be an equivalent here for being liberal in what you accept.
5. Security Considerations
This document articulates a set of Best Current Practices for privacy
that extend the IETF's existing security principles. At times,
privacy and security may appear to be in tension. For example,
adherence to the recommendation in this BCP to minimize the use of
personal data will likely yield less use of persistent identifiers
associated with individual users. Reducing the use of persistent
identifiers can help attackers shield their identities and activities
just as it can for legitimate users. However, even relatively
unsophisticated attackers already have at their disposal a variety of
tools for cloaking their identities. Recommending the minimization
of personal data use at the protocol level can benefit the vast
majority of legitimate users who depend on IETF protocols without
materially improving attackers' existing tools for guarding their
identities.
Similarly, malware and other attack traffic can generally already be
transmitted using object encryption or protocol encryption if
attackers so choose. Recommending that IETF protocols define
mechanisms for opportunistic encryption can increase the availability
of confidentiality protection to legitimate users without
significantly changing the set of tools that attackers already use to
shield their traffic from being identified and their attacks from
being thwarted.
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6. IANA Considerations
This document does not require actions by IANA.
7. Acknowledgements
Thanks to the following for useful comments. These folks may or may
not agree with the content.
Jari Arkko, Bernard Aboba, Scott Brim, Benoit Claise, Nick Doty,
Spencer Dawkins, Eliot Lear, Ted Lemon, SM, Avri Doria, Brian
Trammell, Robin Wilton,
8. Informative References
[RFC1984] IAB, IESG, Carpenter, B., and F. Baker, "IAB and IESG
Statement on Cryptographic Technology and the Internet",
RFC 1984, August 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2804] IAB IESG, "IETF Policy on Wiretapping", RFC 2804, May
2000.
[RFC3365] Schiller, J., "Strong Security Requirements for Internet
Engineering Task Force Standard Protocols", BCP 61, RFC
3365, August 2002.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552, July
2003.
[RFC4322] Richardson, M. and D. Redelmeier, "Opportunistic
Encryption using the Internet Key Exchange (IKE)", RFC
4322, December 2005.
[RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy
Extensions for Stateless Address Autoconfiguration in
IPv6", RFC 4941, September 2007.
[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
Morris, J., Hansen, M., and R. Smith, "Privacy
Considerations for Internet Protocols", RFC 6973, July
2013.
Authors' Addresses
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Alissa Cooper
CDT
1634 Eye St. NW, Suite 1100
Washington, DC 20006
US
Phone: +1-202-637-9800
Email: acooper@cdt.org
URI: http://www.cdt.org/
Stephen Farrell
Trinity College Dublin
Dublin 2
Ireland
Phone: +353-1-896-2354
Email: stephen.farrell@cs.tcd.ie
Sean Turner
IECA, Inc.
3057 Nutley Street, Suite 106
Fairfax, VA 22031
USA
Phone: +1.703.628.3180
Email: turners@ieca.com
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