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Report from the Strengthening the Internet (STRINT) workshop

The information below is for an old version of the document.
Document Type This is an older version of an Internet-Draft that was ultimately published as an RFC.
Authors Stephen Farrell , Rigo Wenning, Bert Bos , Marc Blanchet , Hannes Tschofenig
Last updated 2015-05-28
Stream Internet Architecture Board (IAB)
Stream IAB state IAB Review
Consensus boilerplate Unknown
RFC Editor Note (None)
Network Working Group                                         S. Farrell
Internet-Draft                                   Trinity College, Dublin
Intended status: Informational                                R. Wenning
Expires: November 28, 2015                                        B. Bos
                                                             M. Blanchet
                                                           H. Tschofenig
                                                                ARM Ltd.
                                                            May 27, 2015

      Report from the Strengthening the Internet (STRINT) workshop


   The Strengthening the Internet (STRINT) workshop assembled one
   hundred participants in London for two days in early 2014 to discuss
   how the technical community, and in particular the IETF and the W3C,
   should react to Pervasive Monitoring and more generally how to
   strengthen the Internet in the face of such attacks.  The discussions
   covered issues of terminology, the role of user interfaces, classes
   of mitigation, some specific use cases, transition strategies
   (including opportunistic encryption), and more.  The workshop ended
   with a few high-level recommendations, which it is believed could be
   implemented and which could help strengthen the Internet.  This is
   the report of that workshop.

   Note that this document is a report on the proceedings of the
   workshop.  The views and positions documented in this report are
   those of the workshop participants and do not necessarily reflect IAB
   views and positions.

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

   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."

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   This Internet-Draft will expire on November 28, 2015.

Copyright Notice

   Copyright (c) 2015 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
   Provisions Relating to IETF Documents
   ( in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.

Table of Contents

   1.  Context . . . . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Summary . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Workshop goals  . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Workshop structure  . . . . . . . . . . . . . . . . . . . . .   5
   5.  Topics  . . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   6.  After the workshop  . . . . . . . . . . . . . . . . . . . . .  20
   7.  IANA considerations . . . . . . . . . . . . . . . . . . . . .  21
   8.  Security considerations . . . . . . . . . . . . . . . . . . .  21
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  21
   Appendix A.  Logistics  . . . . . . . . . . . . . . . . . . . . .  25
   Appendix B.  Agenda . . . . . . . . . . . . . . . . . . . . . . .  26
   Appendix C.  Workshop chairs & program committee  . . . . . . . .  28
   Appendix D.  Participants . . . . . . . . . . . . . . . . . . . .  28
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  33

1.  Context

   The Vancouver IETF plenary[vancouverplenary] concluded that Pervasive
   Monitoring (PM) represents an attack on the Internet, and the IETF
   has begun to carry out the more obvious actions required to try to
   handle this attack.  However, there are additional much more complex
   questions arising that need further consideration before any
   additional concrete plans can be made.

   The W3C [1] and IAB [2] therefore decided to host a workshop [3] on
   the topic of "Strengthening the Internet Against Pervasive
   Monitoring" before IETF 89 [4] in London in March 2014.  The
   FP7-funded STREWS [5] project organised the STRINT workshop on behalf
   of the IAB and W3C.

   The main workshop goal was to discuss what can be done, especially by
   the two standards organisations IETF and W3C, against PM, both for

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   existing Internet protocols (HTTP/1, SMTP, etc.) and for new ones
   (WebRTC, HTTP/2, etc.).

   The starting point for the workshop was the existing IETF consensus
   that PM is an attack[RFC7258] (the text of which had achieved IEFF
   consensus at the time of the workshop, even though the RFC had yet to
   be published).

2.  Summary

   The workshop was well attended (registration closed when the maximum
   capacity of 100 was reached, but more than 150 expressed a desire to
   register) and several people (about 165 at the maximum) listened to
   the streaming audio.  The submitted papers (67 in total) were
   generally of good quality and all were published, except for a few
   where authors who couldn't take part in the workshop preferred not to

   The chairs of the workshop summarised the workshop in the final
   session in the form of the following recommendations:

   1.   Well-implemented cryptography can be effective against PM and
        will benefit the Internet if used more, despite its cost, which
        is steadily decreasing anyway.

   2.   Traffic analysis also needs to be considered, but is less well
        understood in the Internet community: relevant research and
        protocol mitigations such as data minimisation need to be better

   3.   Work should continue on progressing the PM threat model
        draft[I-D.barnes-pervasive-problem] discussed in the workshop.

   4.   Later, the IETF may be in a position to start to develop an
        update to BCP 72 [RFC3552], most likely as a new RFC enhancing
        that BCP and dealing with recommendations on how to mitigate PM
        and how to reflect that in IETF work.

   5.   The term "Opportunistic" has been widely used to refer to a
        possible mitigation strategy for PM.  The community need to
        document definition(s) for this term, as it is being used
        differently by different people and in different contexts.  We
        may also be able to develop a cookbook-like set of related
        protocol techniques for developers.  Since the workshop, the
        IETF's security area has taken up this work, most recently
        favouring the generic term "Opportunistic Security" (OS)
        [I-D.kent-opportunistic-security].  Subsequent work on this

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        topic resulted in the publication of a definition of OS in

   6.   The technical community could do better in explaining the real
        technical downsides related to PM in terms that policy makers
        can understand.

   7.   Many User Interfaces (UIs) could be better in terms of how they
        present security state, though this is a significantly hard
        problem.  There may be benefits if certain dangerous choices
        were simply not offered anymore.  But that could require
        significant co-ordination among competing software makers,
        otherwise some will be considered "broken" by users.

   8.   Further discussion is needed on ways to better integrate UI
        issues into the processes of IETF and W3C.

   9.   Examples of good software configurations that can be cut-and-
        paste'd for popular software, etc., can help.  This is not
        necessarily standards work, but maybe the standards
        organisations can help and can work with those developing such
        package-specific documentation.

   10.  The IETF and W3C can do more so that default ("out-of-the-box")
        settings for protocols better protect security and privacy.

   11.  Captive portals [6] (and some firewalls, too) can and should be
        distinguished from real man-in-the-middle attacks.  This might
        mean establishing common conventions with makers of such
        middleboxes, but might also need new protocols.  However, the
        incentives for deploying such new middlebox features might not

3.  Workshop goals

   As stated, the STRINT workshop started from the position [RFC7258]
   that PM is an attack.  While some dissenting voices are expected and
   need to be heard, that was the baseline assumption for the workshop,
   and the high-level goal was to provide more consideration of that and
   how it ought to affect future work within the IETF and W3C.

   At the next level down the goals of the STRINT workshop were to:

   o  Discuss and hopefully come to agreement among the participants on
      concepts in PM for both threats and mitigation, e.g.,
      "opportunistic" as the term applies to cryptography.

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   o  Discuss the PM threat model, and how that might be usefully
      documented for the IETF at least, e.g., via an update to BCP72.

   o  Discuss and progress common understanding in the trade-offs
      between mitigating and suffering PM.

   o  Identify weak links in the chain of Web security architecture with
      respect to PM.

   o  Identify potential work items for the IETF, IAB, IRTF and W3C that
      would help mitigate PM.

   o  Discuss the kinds of action outside the IETF/W3C context might
      help those done within the IETF/W3C.

4.  Workshop structure

   The workshop structure was designed to maximise discussion time.
   There were no direct presentations of submitted papers.  Instead, the
   moderators of each session summarised topics that the Technical
   Programme Committee (TPC) had agreed based on the submitted papers.
   These summary presentations took at most 50% of the session and
   usually less.

   Because the papers would not be presented during the workshop,
   participants were asked to read and discuss the papers beforehand, at
   least those relevant to their fields of interest.  (To help people
   choose papers to read, authors were asked to provide short

   Most of the sessions had two moderators, one to lead the discussion,
   while the other managed the queue of people who wanted to speak.
   This worked well: everybody got a chance to speak and each session
   still ended on time.

   The penultimate session consisted of break-outs (which turned out to
   be the most productive sessions of all, most likely simply due to the
   smaller numbers of people involved).  The subjects for the break-outs
   were agreed during the earlier sessions and just before the break-out
   session the participants collectively determined who would attend

5.  Topics

   The following sections contain summaries of the various sessions.
   See the minutes (see Appendix B) for more details.

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5.1.  Opening session

   The first session discussed the goals of the workshop.  Possible
   approaches to improving security in the light of pervasive monitoring
   include a critical look at what metadata is actually required,
   whether old (less secure) devices can be replaced with new ones, what
   are "low-hanging fruit" (issues that can be handled quickly and
   easily), and what level of security is "good enough": a good solution
   may be one that is good for 90% of people or 90% of organisations.

   Some participants felt that standards are needed so that people can
   see if their systems conform to a certain level of security, and easy
   to remember names are needed for those standards, so that a buyer can
   immediately see that a product "conforms to the named intended

5.2.  Threats

   One difference between "traditional" attacks and pervasive monitoring
   is modus-operandi of the attacker: typically, one determines what
   resources an attacker might want to target and at what cost and then
   one defends against that threat.  But a pervasive attacker has no
   specific targets, other than to collect everything he can.  The
   calculation of the cost of losing resources vs. the cost of
   protecting them is thus different.  And unlike someone motivated to
   make money, a PM attacker may not be concerned at the cost of the
   attack (or may even prefer a higher cost, for "empire building"

   The terminology used to talk about threats has to be chosen carefully
   (this was a common theme in several sessions), because we need to
   explain to people outside the technical community what they need to
   do or not do.  For example, authentication of endpoints doesn't so
   much "protect against" man-in-the-middle (MITM) attacks as make them
   visible.  The attacker can still attack, but it does not remain
   invisible while he does so.  Somebody on either end of the
   conversation needs to react to the alert from the system: stop the
   conversation or find a different channel.

   An interesting paradox is the role of big repositories of
   information, such as Facebook, Yahoo, Google, etc.  Hopefully, they
   supervise their security better than the average Internet server, but
   they are also much more attractive as a target to attack.  Avoiding
   overuse of such repositories for private or sensitive information may
   be a useful measure that increases the cost of collecting for a
   pervasive attacker.  This is sometimes called the target-dispersal

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   Lack of interoperability between systems is in itself a threat as it
   leads to work-arounds and compromises that may be less secure.  And
   thus improving interoperability needs to be high on the list of
   priorities of standards makers and even more for implementers.  Of
   course, testing, such as interop testing, is at some level, part of
   the process of IETF and W3C; and W3C is currently increasing its
   testing efforts.

5.3.  Increase usage of security tools

   The first session on Communication Security (COMSEC) tools looked at
   the question why existing security tools aren't used more.

   The example of HTTPS is informative: it provides encryption and
   authentication and is widely available.  In practice though, it is
   far from being used as much as it could be.  It also has some
   problems.  One problem is that certificate authorities (CA) are a
   potential weak link in the system.  Any CA can issue a certificate
   for any server, and thus a single compromised CA can give a MITM the
   power to impersonate any server.  Moreover, certificates can cost
   money, acquiring a certificate requires administrator time and
   effort, and certificates need to be replaced when they expire, which
   is not the normal case for web technologies, so many server
   administrators forget or don't bother, making the certificate
   infrastructure less relevant, and causing HTTPS to provide less

   Some ideas were discussed for improving the CA system, e.g., via
   cross-certification of CAs and by means of "certificate
   transparency": a public, permanent log of who issued which
   certificate.  [RFC6962]

   Using other models than the hierarchical certificate model (as
   alternative or in combination) may also help.  The PGP model, e.g.,
   is a flat network where people verify the identity (public key) of
   people they meet.  And then they trust, to a certain level, that
   those people verified the identity of other people.  This works for
   certain types of communication (it was more deployed for e-mail).
   However, an identity only verified by a friend of a friend provides a
   lower level of trust.

   Yet another model is "trust on first use" (TOFU).  This is used quite
   effectively by SSH [RFC4252].  On the first connection, one has no
   way to verify that the received public key belongs to the server one
   is contacting, therefore, the key is accepted without further
   verification.  But on the subsequent connections, one can verify that
   the received key is the same key as the first time.  So a MITM has to

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   be there on all connections, including the first, otherwise it will
   be detected by a key mismatch.

   This works well for SSH, because people typically use SSH to
   communicate with a small number of servers over and over again.  And,
   if they want, they may find a separate channel to get the public key
   (or its fingerprint).  It may also work for Web servers used by small
   groups (the server of a sports club, a department of a company,
   etc.), but probably works less well for public servers that are
   visited once or a few times or for large services where many servers
   may be used.

   A similar proposal [draft-ietf-websec-key-pinning] for an HTTP header
   introduces an aspect of TOFU into HTTP: Key pinning tells HTTP
   clients that for a certain time after receiving this certificate,
   they should not expect the certificate to change.  If it does, even
   if the new certificate looks valid, the client should assume a
   security breach.

   SIP [RFC3261] is a complex protocol, in part because it potentially
   needs several different intermediaries in different stages of the
   communication to deal with NAT traversal and to handle policy.  SIP
   provides hop-by-hop encryption and end-to-end authentication in
   theory, but in practice many SIP providers disable these functions
   and interoperability for end-to-end security in SIP is perhaps not in
   a good state.  The reasons for disabling end-to-end security here are
   understandable: to overcome lack of interoperability they often need
   to change protocol headers and modify protocol data.  Some workshop
   participants argued that SIP would never have taken off if it hadn't
   been possible for providers to monitor and interfere in
   communications in this way.  Of course, that means an attacker can
   listen in just as easily.

   A new protocol for peer-to-peer communication of video and audio (and
   potentially other data) is WebRTC.  WebRTC re-uses many of the same
   architectural concepts as SIP, but there is a reasonable chance that
   it can do better in terms of protecting users: The people
   implementing the protocols and offering the service have different
   goals and interests.  In particular, the first implementers are
   browser makers, who may have different business models from other
   more traditional Voice over IP providers.

   XMPP[RFC6120] suffers from yet another problem.  It has encryption
   and authentication, and the OTR ("off the record") extension even
   provides what is called Perfect Forward Secrecy (PFS, compromising
   the current communication never gives an attacker enough information
   to decrypt past communications that he may have recorded).  But, in
   practice, many people don't use XMPP at all, but rather Skype,

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   WhatsApp or other instant-messaging tools with unknown or no
   security.  The problem here seems to be one of user awareness.  And
   though OTR does provide security, it is not well integrated with XMPP
   and nor is it available as a core feature of XMPP clients.

   To increase usage of existing solutions, some tasks can be
   identified, though how those map to actions for e.g.  IETF/W3C is not

   o  Improvements to the certificate system, such as certificate
      transparency (CT).

   o  Making it easier (cheaper, quicker) for system administrators to
      deploy secure solutions.

   o  Improve awareness of the risks.  Identify which communities
      influence which decisions and what is the appropriate message for

   o  Provide an upgrade path that doesn't break existing systems or
      require that everybody upgrade at the same time.  Opportunistic
      Security may be one model for that.

5.4.  Policy issues and non-technical actions

   Previous sessions already concluded that the problem isn't just
   technical, such as getting the right algorithms in the standards,
   fixing interoperability, or educating implementers and systems
   administrators.  There are user interface issues and education issues
   too.  And there are also legal issues and policy issues for

   It appears that the public in general demand more privacy and
   security (e.g., for their children) but are also pessimistic about
   getting that.  They trust that somebody assures that nothing bad
   happens to them, but they also expect to be spied on all the time.

   (Perceived) threats of terrorism gave governments a reason to allow
   widespread surveillance, far beyond what may previously have been
   considered dangerous for freedom.

   In this environment, the technical community will have a hard time
   developing and deploying technologies that fully counter PM, which
   means there has to be action in the social and political spheres,

   Technology isn't the only thing that can make life harder for
   attackers.  Government-sponsored PM is indirectly affected by trade

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   agreements and treaties and thus it makes sense to lobby for those to
   be as privacy-friendly as possible.

   Court cases on the grounds of human rights can also influence policy,
   especially if they reach, for example, the European Court of Human

   In medicine and law, it is common to have ethics committees, not so
   in software.  Should standards bodies such as IETF and W3C have an
   ethics committee?  Standards such as the Geolocation API
   [w3c-geo-api] have gotten scrutiny from privacy experts, but only in
   an ad-hoc manner.  (W3C has permanent groups to review standards for
   accessibility and internationalisation.  It also has a Privacy group,
   but that currently doesn't do the same kind of systematic reviews.)

   As the Internet Draft draft-barnes-pervasive-problem-00 (included as
   paper 44 [8]) explains, PM doesn't just monitor the networks, but
   also attacks at the endpoints, turning organisations or people into
   (willing, unwilling, or unwitting) collaborators.  One technical
   means of protection is thus to design protocols such that there are
   fewer potential collaborators, e.g., a provider of cloud storage
   cannot hand over plaintext for content that is encrypted with a key
   he doesn't have, and cannot hand over names if his client is

   It is important to distinguish between PM and fighting crime.  PM is
   an attack, but a judge ordering the surveillance of a suspected
   criminal is not.  The latter, often abbreviated in this context as LI
   (for Lawful Intercept), is outside the scope of this workshop.

5.5.  Improving the tools

   An earlier session discussed why existing COMSEC tools weren't used
   more.  This second session on COMSEC therefore discussed what
   improvements and/or new tools were needed.

   Discussion at the workshop indicated that an important meta-tool for
   improving existing security technology could be Opportunistic
   Security (OS) [I-D.kent-opportunistic-security].  The idea is that
   software is enhanced with a module that tries to encrypt
   communications when it detects that the other end also has the same
   capability but otherwise lets the communication continue in the old
   way.  The detailed definition of OS is being discussed by the IETF
   security area at the time of this workshop [saag].

   OS would protect against a passive eavesdropper but should also allow
   for endpoint authentication to protect against an active attacker (a
   MITM).  As OS spreads, more and more communications would be

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   encrypted (and hopefully authenticated) and thus there is less and
   less for an eavesdropper to collect.

   Of course, an implementation of OS could give a false sense of
   security as well: some connections are encrypted, some are not.  A
   user might see something like a padlock icon in browsers, but there
   was agreement at the workshop that such user interface features ought
   not be changed because OS is being used.

   There is also the possibility that a MITM intercepts the reply from a
   server that says "yes, I can do encryption" and removes it, causing
   the client to fall back to an unencrypted protocol.  Mitigations
   against this can be to have other channels of finding out a server's
   capabilities and remembering that a server could do encryption

   There is also, again, a terminology problem.  The technical
   descriptions of OS talk about "silent fail" when a connection
   couldn't be encrypted and has to fall back to the old, unencrypted
   protocol.  Actually, it's not a fail; it's no worse than it was
   before.  A successful encryption would rather be a "silent

   That raises the question of the UI: How do you explain to a user what
   their security options are, and, in case an error occurs, how do you
   explain the implications of the various responses?

   The people working on encryption are mathematicians and engineers,
   and typically not the same people who know about UI.  We need to
   involve the experts.  We also need to distinguish between usability
   of the UI, user understanding, and user experience.  For an
   e-commerce site, e.g., it is not just important that the user's data
   is technically safe, but also that he feels secure.  Otherwise he
   still won't buy anything.

   When talking about users, we also need to distinguish the end user
   (who we typically think about when we talk about UI) from the server
   administrators and other technical people involved in enabling a
   connection.  When something goes wrong (e.g., the user's software
   detects an invalid certificate), the message usually goes to the end
   user.  But he isn't necessarily the person who can do something about
   it.  E.g., if the problem is a certificate that expired yesterday,
   the options for the user are to break the connection (the safe
   choice, but it means he can't get his work done) or continue anyway
   (there could be a MITM...).  The server administrator, on the other
   hand, could actually solve the problem.

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   Encryption and authentication have a cost, in terms of setting them
   up, but also in terms of the time it takes for software to do the
   calculations.  The set-up cost can be reduced with sensible defaults,
   predefined profiles and cut-and-paste configurations.  And for some
   connections, authentication without encryption could be enough, in
   the case that the data doesn't need to be kept secret, but it is
   important to know that it is the real data.  Most mail user agents
   (UA) already provide independent options for encryption and signing,
   but Web servers only support authentication if the connection is also

   On the other hand, as e-mail also shows, it is difficult for users to
   understand what encryption and authentication do separately.

   And it also has to be kept in mind that encrypting only the
   "sensitive" data and not the rest decreases the cost for an attacker,
   too: It becomes easy to know which connections are worth attacking.
   Selective field confidentiality is also more prone to lead to
   developer error, as not all developers will know the provenance of
   values to be processed.

   One problem with the TOFU model as used by SSH (see explanation
   above) is that it lacks a solution for key continuity: When a key is
   changed (which can happen, e.g., when a server is replaced or the
   software upgraded), there is no way to inform the client.  (In
   practice, people use other means, such as calling people on the phone
   or asking their colleagues in the office, but that doesn't scale and
   doesn't always happen either.)  An improvement in the SSH protocol
   could thus be a way to transfer a new key to a client in a safe way.

5.6.  Hiding metadata

   Encryption and authentication help protect the content of messages.
   Correctly implemented encryption is very hard to crack.  (To get the
   content, an attacker would rather attempt to steal the keys, corrupt
   the encoding software, or get the content via a collaborator.)  But
   encrypting the content doesn't hide the fact that you are
   communicating.  This metadata (who talks to whom, when and for how
   long) is often as interesting as the content itself, and in some
   cases the size and timing of messages is even an accurate predictor
   of the content.  So how to stop an attacker from collecting metadata,
   given that much of that data is actually needed by routers and other
   services to deliver the message to the right place?

   It is useful to distinguish different kinds of metadata: explicit (or
   metadata proper) and implicit (sometimes called traffic data).
   Implicit metadata is things that can be derived from a message or are
   necessary for its delivery, such as the destination address, the

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   size, the time, or the frequency with which messages pass.  Explicit
   metadata is things like quality ratings, provenance or copyright
   data: data about the data, useful for an application, but not
   required to deliver the data to its endpoint.

   A system such as Tor hides much of the metadata by passing through
   several servers, encrypting all the data except that which a
   particular server needs to see.  Each server thus knows which server
   a message came from and where he has to send it to, but cannot know
   where the previous server got it from or where the next server is
   instructed to send it.  However, deliberately passing through
   multiple servers makes the communication slower than taking the most
   direct route and increases the amount of traffic the network as a
   whole has to process.

   There are three kinds of measures that can be taken to make metadata
   harder to get: aggregation, contraflow and multipath (see paper 4
   [9]).  New protocols should be designed such that these measures are
   not inadvertently disallowed, e.g., because the design assumes that
   the whole of a conversation passes through the same route.

   "Aggregation" means collecting conversations from multiple sources
   into one stream.  E.g., if HTTP connections pass through a proxy, all
   the conversations appear to come from the proxy instead of from their
   original sources.  (This assumes that telltale information in the
   headers is stripped by the proxy, or that the connection is
   encrypted.)  It also works in the other direction: if multiple Web
   sites are hosted on the same server, an attacker cannot see which of
   those Web sites a user is reading.  (This assumes that the name of
   the site is in the path info of the URL and not in the domain name,
   otherwise watching DNS queries can still reveal the name.)

   "Contraflow" means routing a conversation via one or more other
   servers than the normal route, e.g., by using a tunnel (e.g., with
   SSH or a VPN) to another server.  Tor is an example of this.  An
   attacker must watch more routes and do more effort to correlate
   conversations.  (Again, this assumes that there is no telltale
   information left in the messages that leave the tunnel.)

   "Multipath" splits up a single conversation (or a set of related
   conversations) and routes the parts in different ways.  E.g., sending
   a request via a satellite link and receiving the response via a land
   line; or starting a conversation on a cellular link and continuing it
   via Wi-Fi.  This again increases the cost for an attacker, who has to
   monitor and correlate multiple networks.

   Protecting metadata automatically with technology at a lower layer
   than the application layer is difficult.  The applications themselves

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   need to pass less data, e.g., use anonymous temporary handles instead
   of permanent identifiers.  There is often no real need for people to
   use the same identifier on different computers (smartphone, desktop,
   etc.) other than that the application they use was designed that way.

   One thing that can be done relatively easily in the short term is to
   go through existing protocols to check what data they send that isn't
   really necessary.  One candidate mentioned for such a study was XMPP.

   "Fingerprinting" is the process of distinguishing different senders
   of messages based on metadata: Clients can be recognised (or at least
   grouped) because their messages always have a combination of features
   that other clients do not have.  Reducing redundant metadata and
   reducing the number of optional features in a protocol reduces the
   variation between clients and thus makes fingerprinting harder.

   Traffic analysis is a research discipline that produces sometimes
   surprising findings, which are little known among protocol
   developers.  Some collections of results are

   o  A selected bibliography on anonymity [10] by the Free Haven

   o  The yearly Symposium on Privacy Enhancing Technologies (PETS)
      [11], and

   o  The yearly Workshop on Privacy in the Electronic Society (WPES)

   Techniques that deliberately change the timing or size of messages,
   such as padding, can also help reduce fingerprinting.  Obviously,
   they make conversations slower and/or use more bandwidth, but in some
   cases that is not an issue, e.g., if the conversation is limited by
   the speed of a human user anyway.  HTTP/2 has a built-in padding
   mechanism.  However, it is not so easy to use these techniques well,
   and not actually make messages easier to recognise rather than

   Different users in different contexts may have different security
   needs, so maybe the priority can be a user choice (if that can be
   done without making high-security users stand out from other users).
   Although many people would not understand what their choices are,
   some do, such as political activists or journalists.

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5.7.  Deployment, intermediaries and middleboxes

   Secure protocols have often been designed in the past for end-to-end
   security: Intermediaries cannot read or modify the messages.  This is
   the model behind TLS for example.

   In practice, however, people have more or less valid reasons to
   insist on intermediaries: companies filtering incoming and outgoing
   traffic for viruses or other reasons, giving priority to certain
   communications or caching to reduce bandwidth.

   In the presence of end-to-end encryption and authentication, these
   intermediaries have two choices: use fake certificates to impersonate
   the endpoints or have access to the private keys of the endpoints.
   The former is a MITM attack that is difficult to distinguish from a
   more malicious one, and the latter obviously decreases the security
   of the endpoints by copying supposedly protected data and
   concentrating such data in a single place.

   As mentioned in Section 5.2 above, aggregation of data in a single
   place makes that place an attractive target.  And in the case of PM
   even if the data is not concentrated physically in one place, it is
   under control of a single legal entity that can be made into a

   The way Web communication with TLS typically works is that the client
   authenticates the server, but the server does not authenticate the
   client at the TLS layer.  (If the client needs to be identified, that
   is mainly done at the application layer via passwords or cookies.)
   Thus the presence of a MITM (middlebox) could be detected by the
   client (because of the incorrect certificate), but not by the server.
   If the client doesn't immediately close the connection (which they do
   not in many cases), the server may thus disclose information that the
   user would rather not have disclosed.

   One widespread example of middleboxes is captive portals, as found on
   the Wi-Fi hotspots in hotels, airports, etc.  Even the hotspots
   offering free access often intercept communications to redirect the
   user to a login or policy page.

   When the communication they intercept is, e.g., the automatic update
   of your calendar program or a chat session, the redirect obviously
   doesn't work: these applications don't know how to display a Web
   page.  With the increasing use of applications, it may be a while
   before the user actually opens a browser.  The flood of error
   messages may also have as a result that the user no longer reads the
   errors, allowing an actual malicious attack to go unnoticed.

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   Some operating systems now come with heuristics that try to recognise
   captive portals and either automatically login or show their login
   page in a separate application.  (But some hotspot providers
   apparently don't want automatic logins and actually reverse-
   engineered the heuristics to try and fool them.)

   It seems some protocol is missing in this case.  Captive portals
   shouldn't have to do MITM attacks to be noticed.  Something like an
   extension to DHCP that tells a connecting device about the login page
   may help, although that still doesn't solve the problem for devices
   that do not have a Web browser, such as game consoles or SIP phones.
   HTTP response code 511 (defined in [RFC6585]) is another attempt at a
   partial solution (Partial, because it can only work at the moment the
   user uses a browser to connect to a Web site and doesn't use HTTPS).

   A practical problem with deployment of such a protocol may be that
   many such captive portals are very old and never updated.  The hotel
   staff only knows how to reboot the system and as long as it works,
   the hotel has no incentive to buy a new one.  As evidence of this:
   how many such systems require you to get a password and the ticket
   shows the price as zero?  This is typically because the owner doesn't
   know how to reconfigure the hotspot, but he does know how to change
   the price in his cash register.

5.8.  Break-out 1 - research

   Despite some requests earlier in the workshop, the research break-out
   did not discuss clean-slate approaches.  The challenge was rather
   that the relationship between security research and standardisation
   needs improvement.  Research on linkability is not yet well known in
   the IETF.  But the other side of the coin needs improvement too:
   While doing protocol design, standardisation should indicate what
   specific problems are in need of more research.

   The break-out then made a non-exclusive list of topics that are in
   need of further research:

   o  The interaction of compression and encryption as demonstrated by
      the CRIME SSL/TLS vulnerability [13]

   o  A more proactive deprecation of algorithms based on research

   o  Mitigation for return-oriented programming attacks

   o  How to better obfuscate so called "metadata"

   o  How to make the existence of traffic and their endpoints stealthy

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5.9.  Break-out 2 - clients

   Browsers are the first clients one thinks of when talking about
   encrypted connections, authentication and certificates, but there are
   many others.

   Other common case of "false" alarms for MITM (after captive portals)
   include expired and mis-configured certificates.  This is quite
   common in intranets, when the sysadmin hasn't bothered updating a
   certificate and rather tells his handful of users to just "click
   continue."  The problem is on the one hand that users may not
   understand the difference between this case and the same error
   message when they connect to a server outside the company, and on the
   other hand that the incorrect certificate installed by the sysadmin
   is not easily distinguishable from an incorrect certificate from a
   MITM.  The error message is almost the same and the user may just
   click continue again.

   One way to get rid of such certificates is if client software no
   longer offers the option to continue after a certificate error.  That
   requires that all major clients (such as browsers) change their
   behaviour at the same time, otherwise the first one to do so will be
   considered broken by users, because the others still work.  Also it
   requires a period in which that software gives increasingly strong
   warnings about the cut-off date after which the connection will fail
   with this certificate.

   Yet another source of error messages is self-signed certificates.
   Such certificates are actually only errors for sites that are not
   expected to have them.  If a message about a self-signed certificate
   appears when connecting to Facebook or Google, you're clearly not
   connected to the real Facebook or Google.  But for a personal Website
   it shouldn't cause such scary warnings.  There may be ways to improve
   the explanations in the error message and provide an easy way to
   verify the certificate (by e-mail, over the phone or some other
   channel) and trust it.

5.10.  Break-out 3 - on by default

   One step in improving security is to require the relevant features,
   in particular encryption and authentication, to be implemented in
   compliant products: The features are labelled as MUST in the standard
   rather than MAY.  This is sometimes referred to as Mandatory To
   Implement (MTI) and is the current practice for IETF

   But that may not be enough to counter PM.  It may be that the
   features are there, but not used, because only very knowledgeable

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   users or sysadmins turn them on.  Or it may be that implementations
   do not actually follow the MTI parts of specifications.  Or it may be
   that some security features are implemented but interoperability for
   those doesn't really work.  Or, even worse, it may be that protocol
   designers have only followed the letter of the MTI best practice and
   not its spirit, with the result that security features are hard to
   use or make deployment harder.  One can thus argue that such features
   should be defined to be on by default.

   Going further one might argue that these features should not even be
   options, i.e., there should be no way to turn them off.  This is
   sometimes called Mandatory To Use (MTU).

   The question raised at this session was for what protocols on-by-
   default is appropriate, and how can one explain to the developers of
   such protocols that it is needed?

   There would of course be resistance to MTU security from implemeters
   and deployments that practice deep packet inspection (DPI) and also
   perhaps from some governments.  On the other hand, there may also be
   governments that outlaw protocols without proper encryption.

   This break-out concluded that there could be value in attempting to
   document a new Best Current Practice for the IETF that moves from the
   current MTI position to one where security features are on-by-
   default.  Some of the workshop participants expressed interest in
   authoring a draft for such a new BCP and progressing that through the
   IETF consensus process (where it would no doubt be controversial).

5.11.  Break-out 4 - measurement

   There was a small break-out on the idea of measurement as a way to
   encourage or gamify the increased use of security mechanisms.

5.12.  Break-out 5 - opportunistic

   This break out considered the use of the term "opportunistic" as it
   applies to cryptographic security and attempted to progress the work
   towards arriving at an agreed-upon definition for use of that term,
   at it applies to IETF and W3C work.

   While various terms had been used, with many people talking about
   opportunistic encryption, that usage was felt to be problematic both
   because it conflicted with the use of the same term in [RFC4322] and
   because it was being used differently in different parts of the

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   At the session it was felt that the term "opportunistic keying" was
   better, but as explained above subsequent list discussion resulted in
   a move to the term "Opportunistic Security" (OS).

   Aside from terminology, disussion focused on the use of Diffie-
   Hellman (D-H) key exchange as the preferred mechanism of OS, with
   fall back to cleartext if D-H doesn't succeed as a counter for
   passive attacks.

   There was also of course the desire to be able to easily escalate
   from countering passive attacks to also handling endpoint
   authentication and thereby also countering MITM attacks.

   Making OS visible to users was again considered to be undesirable, as
   users could not be expected to distinguish between cleartext, OS and
   (one-sided or mutual) endpoint authentication.

   Finally, it was noted that it may take some effort to establish how
   middleboxes might affect OS at different layers and that OS really is
   not suitable as the only migitation to use for high-sensitivity
   sessions such as financial transactions.

5.13.  Unofficial Transport/Routing Break-out

   Some routing and transport area directors felt a little left out by
   all the application layer break-outs, so they had their own
   brainstorm about what could be done at the Transport and Routing
   layers from which these notes resulted.

   The LEDBAT [RFC6817] protocol was targeted towards a bulk-transfer
   service that is reordering and delay insensitive.  Use of LDEBAT
   could offer the following benefits for an application:

   a.  Because it is reordering-insensitive, traffic can be sprayed
       across a large number of forwarding paths.  Assuming such
       different paths exist, this would make it more challenging to
       capture and analyze a full interaction.

   b.  The application can vary the paths by indicating per packet a
       different flow.  In IPv6, this can be done via different IPv6
       flow labels.  For IPv4, this can be done by encapsulating the IP
       packet into UDP and varying the UDP source port.

   c.  Since LEDBAT is delay-insensitive and applications using it would
       need to be as well, it would be possible to obfuscate the
       application signatures by varying the packet lengths and

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   d.  This can also hide the transport header (for IP in UDP).

   e.  If the Reverse Path Forwarding(RPF)[RFC3704] check problem can be
       fixed, perhaps the source could be hidden, however it assumes the
       trafic is within trusted perimeters.

   f.  The use of LEDBAT is orthogonal to the use of encryption and
       provides different benefits (harder to intercept the whole
       conversation, ability to obfuscate the traffic analysis), and
       also has different costs (longer latency, new transport protocol
       usage) to its users.

   The idea of encrypting traffic from customer edge (CE) to CE as part
   of an L3VPN or such was also discussed.  This could allow hiding of
   addresses, including source, and headers.  From conversation with Ron
   Bonica, some customers already do encryption (though not hiding the
   source address) like this.  So, it is unclear that this is very
   practically useful as an enhancement except for encouraging
   deployment and use.

   Finally, it was discussed whether it would be useful to have a means
   of communicating where and what layers are doing encryption on an
   application's traffic path.  The initial idea of augmenting ICMP has
   some issues (not visible to application, ICMP packets frequently
   filtered) as well as potential work (determining how to trust the
   report of encryption).  It would be interesting to understand if such
   communication is actually needed and what the requirements would be.

6.  After the workshop

   Holding the workshop just before the IETF had the intended effect: a
   number of people went to both the workshop and the IETF, and they
   took the opportunity of being together at the IETF to continue the

   IETF Working groups meeting in London took the recommendations from
   the workshop into account.  It was even the first item in the report
   about the IETF meeting by the IETF chair, Jari Arkko:

      "Strengthening the security and privacy of the Internet continued
      to draw a lot of attention.  The STRINT workshop organised by the
      IAB and W3C just before the IETF attracted 100 participants and
      over 60 papers.  Even more people would have joined us, but there
      was no space.  During the IETF meeting, we continued discussing
      the topic at various working groups.  A while ago we created the
      first working group specifically aimed at addressing some of the
      issues surrounding pervasive monitoring.  The Using TLS for
      Applications (UTA) working group had its first meeting in London.

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      But many other working groups also address these issues in their
      own work.  The TCPM working group discussed a proposal to add
      opportunistic keying mechanisms directly onto the TCP protocol.
      And the DNSE BOF considered the possibility of adding
      confidentiality support to DNS queries.  Finally, there is an
      ongoing effort to review old specifications to search for areas
      that might benefit from taking privacy and data minimisation
      better into account."[Arkko1]

   Two papers that were written for the workshop, but not finished in
   time, are worth mentioning, too: One by the same Jari Arkko, titled
   "Privacy and Networking Functions" [Arkko2]; and one by Johan
   Pouwelse, "The Shadow Internet: liberation from Surveillance,
   Censorship and Servers" [draft-pouwelse-perpass-shadow-internet]

7.  IANA considerations

   There are none.  We hope the RFC editor deletes this section.

8.  Security considerations

   This document does not define a technology but is all about security
   and privacy.

9.  References

9.1.  Informative references

   [Arkko1]   Arkko, J., "IETF-89 Summary", March 2014,

   [Arkko2]   Arkko, J., "Privacy and Networking Functions", March 2014,

              (Work in progress.)

              Evans, C., Palmer, C., and R. Sleevi, "Public Key Pinning
              Extension for HTTP", February 2014.

              (Work in progress.)

              Pouwelse, J., Ed., "The Shadow Internet: liberation from
              Surveillance, Censorship and Servers", February 2014,

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              (Work in progress.)

              Barnes, R., Schneier, B., Jennings, C., and T. Hardie,
              "Pervasive Attack: A Threat Model and Problem Statement",
              draft-barnes-pervasive-problem-01 (work in progress), July

              Kent, S., "Opportunistic Security as a Countermeasure to
              Pervasive Monitoring", draft-kent-opportunistic-
              security-01 (work in progress), April 2014.

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              June 2002.

   [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

   [RFC3704]  Baker, F. and P. Savola, "Ingress Filtering for Multihomed
              Networks", BCP 84, RFC 3704, March 2004.

   [RFC4252]  Ylonen, T. and C. Lonvick, "The Secure Shell (SSH)
              Authentication Protocol", RFC 4252, January 2006.

   [RFC4322]  Richardson, M. and D. Redelmeier, "Opportunistic
              Encryption using the Internet Key Exchange (IKE)", RFC
              4322, December 2005.

   [RFC6120]  Saint-Andre, P., "Extensible Messaging and Presence
              Protocol (XMPP): Core", RFC 6120, March 2011.

   [RFC6585]  Nottingham, M. and R. Fielding, "Additional HTTP Status
              Codes", RFC 6585, April 2012.

   [RFC6817]  Shalunov, S., Hazel, G., Iyengar, J., and M. Kuehlewind,
              "Low Extra Delay Background Transport (LEDBAT)", RFC 6817,
              December 2012.

   [RFC6962]  Laurie, B., Langley, A., and E. Kasper, "Certificate
              Transparency", RFC 6962, June 2013.

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   [RFC7258]  Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
              Attack", BCP 188, RFC 7258, May 2014.

   [RFC7435]  Dukhovni, V., "Opportunistic Security: Some Protection
              Most of the Time", RFC 7435, December 2014.

   [saag]     Area, S., "IETF Security Area mailing list", March 2014,

              IETF, , "IETF 88 Technical Plenary Minutes",

              Popescu, A., "Geolocation API Specification", October
              2013, <>.

9.2.  URIs














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Appendix A.  Logistics

   The workshop was organised by the STREWS [14] project (a research
   project funded under the European Union's 7th Framework Programme
   [15]), as the first of two workshops in its work plan.  The
   organisers were supported by the IAB and W3C, and, for the local
   organisation, by Telefonica Digital. [16]

   One of the suggestions in the project description of the STREWS
   project was to attach the first workshop to an IETF meeting.  The
   best opportunity was IETF 89 [17] in London, which would begin on
   Sunday March 2, 2014.  Telefonica Digital offered meeting rooms at
   its offices in central London for the preceding Friday and Saturday,
   just minutes away from the IETF's location.

   The room held 100 people, which was thought to be sufficient.  There
   turned out to be more interest than expected and we could have filled
   a larger room, but 100 people is probably an upper limit for good
   discussions anyway.

   Apart from the usual equipment in the room (projector, white boards,
   microphones, coffee...), we also set up some extra communication

   o  A mailing list where participants could discuss the agenda and the
      published papers about three weeks in advance of the workshop
      itself.  (Only participants were allowed to write to the mailing
      list, but the archive [18] is public.)

   o  Publicly advertised streaming audio (one-way only).  At some
      point, no less than 165 people were listening.

   o  An IRC channel for live minute taking, passing links and other
      information, and as a help for remote participants to follow the

   o  An Etherpad, where the authors of papers could provide an abstract
      of their submissions, to help participants who could not read all
      66 papers in full in advance of the workshop.  The abstracts were
      also used on the workshop's Web site [19].

   o  A "Twitter hashtag" (#strint).  Four weeks after the workshop,
      there were still a few new messages [20] about events related to
      workshop topics.

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Appendix B.  Agenda

   This was the final agenda of the workshop, as determined by the TPC
   and participants on the mailing list prior to the workshop.  The
   included links are to the slides that the moderators used to
   introduce each discussion topic and to the minutes.

B.1.  Friday 28 February

      Minutes [21]

      Workshop starts, welcome, logistics, opening/overview [slides]

      *  Goal is to plan how we respond to PM threats

      *  Specific questions to be discussed in sessions

      *  Outcomes are actions for IETF, W3C, IRTF, etc.

      I.  Threats - What problem are we trying to solve?  (Presenter:
      Richard Barnes; Moderator: Cullen Jennings) [slides] [23]

      *  What attacks have been described?  (Attack taxonomy)

      *  What should we assume the attackers' capabilities are?

      *  When is it really "pervasive monitoring" and when is it not?

      *  Scoping - what's in and what's out? (for IETF/W3C)

      II.  COMSEC 1 - How can we increase usage of current COMSEC tools?
      (Presenter: Hannes Tschofenig; Moderator: Leif Johansson) [slides]

      *  Whirlwind catalog of current tools

      *  Why aren't people using them?  In what situations are / aren't
         they used?

      *  Securing AAA and management protocols - why not?

      *  How can we (IETF/W3C/community) encourage more/better use?

      III.  Policy - What policy / legal/ other issues need to be taken
      into account?  (Presenter: Christine Runnegar; Moderator: Rigo
      Wenning) [slides] [25]

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      *  What non-technical activities do we need to be aware of?

      *  How might such non-technical activities impact on IETF/W3C?

      *  How might IETF/W3C activities impact on those non-technical

      Session IV - Saturday plan, open-mic, wrap up day

B.2.  Saturday 1 March

      Minutes [26]

      IV.  COMSEC 2 - What improvements to COMSEC tools are
      needed?(Presenter: Mark Nottingham; Moderator: Steve Bellovin)
      [slides] [27]

      *  Opportunistic encryption - what is it and where it might apply

      *  Mitigations aiming to block PM vs. detect PM - when to try

      V.  Metadata - How can we reduce the metadata that protocols
      expose?  (Presenter: Alfredo Pironti [slides] [28] / Ted Hardie
      [slides] [29]; Moderator: Alissa Cooper [slides] [30])

      *  Meta-data, fingerprinting, minimisation

      *  What's out there?

      *  How can we do better?

      VI.  Deployment - How can we address PM in deployment /
      operations?  (Presenter: Eliot Lear; Moderator: Barry Leiba)
      [slides] [31]

      *  "Mega"-commercial services (clouds, large scale email & SN,
         SIP, WebRTC...)

      *  Target dispersal - good goal or wishful thinking?

      *  Middleboxes: when a help and when a hindrance?

      VII. 3 x Break-out Sessions / Bar-Camp style (Hannes Tschofenig)

      *  Content to be defined during meeting, as topics come up

      *  Sum up at the end to gather conclusions for report

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      1.  Research Questions (Moderator: Kenny Paterson)

          +  Do we need more/different crypto tools?

          +  How can applications make better use of COMSEC tools?

          +  What research topics could be handled in IRTF?

          +  What other research would help?

      2.  clients

      3.  on by default

      4.  measuring

      5.  opportunistic

      VIII.  Break-out reports, Open mic & Conclusions - What are we
      going to do to address PM? [slides] [32]

      *  Gather conclusions / recommendations / goals from earlier

Appendix C.  Workshop chairs & program committee

   The workshop chairs were three: Stephen Farrell [33] (TCD) and Rigo
   Wenning [34] (W3C) from the STREWS project, and Hannes Tschofenig
   [35] (ARM) from the STREWS Interest Group.

   A program committee (PC) was charged with evaluating the submitted
   papers.  It was made up of the members of the STREWS project, the
   members of the STREWS Interest Group, plus invited experts: Bernard
   Aboba (Microsoft), Dan Appelquist (Telefonica & W3C TAG), Richard
   Barnes (Mozilla), Bert Bos (W3C), Lieven Desmet (KU Leuven), Karen
   O'Donoghue (ISOC), Russ Housley (Vigil Security), Martin Johns (SAP),
   Ben Laurie (Google), Eliot Lear (Cisco), Kenny Paterson (Royal
   Holloway), Eric Rescorla (RTFM), Wendy Seltzer (W3C), Dave Thaler
   (Microsoft) and Sean Turner (IECA).

Appendix D.  Participants

   The participants to the workshop were:

   o  Bernard Aboba (Microsoft Corporation)

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   o  Thijs Alkemade (Adium)

   o  Daniel Appelquist (Telefonica Digital)

   o  Jari Arkko (Ericsson)

   o  Alia Atlas (Juniper Networks)

   o  Emmanuel Baccelli (INRIA)

   o  Mary Barnes

   o  Richard Barnes (Mozilla)

   o  Steve Bellovin (Columbia University)

   o  Andrea Bittau (Stanford University)

   o  Marc Blanchet (Viagenie)

   o  Carsten Bormann (Uni Bremen TZI)

   o  Bert Bos (W3C)

   o  Ian Brown (Oxford University)

   o  Stewart Bryant (Cisco Systems)

   o  Randy Bush (IIJ / Dragon Research Labs)

   o  Kelsey Cairns (Washington State University)

   o  Stuart Cheshire (Apple)

   o  Vincent Cheval (University of Birmingham)

   o  Benoit Claise (Cisco)

   o  Alissa Cooper (Cisco)

   o  Dave Crocker (Brandenburg InternetWorking)

   o  Leslie Daigle (Internet Society)

   o  George Danezis (University College London)

   o  Spencer Dawkins (Huawei)

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   o  Mark Donnelly (Painless Security)

   o  Nick Doty (W3C)

   o  Dan Druta (AT&T)

   o  Peter Eckersley (Electronic Frontier Foundation)

   o  Lars Eggert (NetApp)

   o  Kai Engert (Red Hat)

   o  Monika Ermert

   o  Stephen Farrell (Trinity College Dublin)

   o  Barbara Fraser (Cisco)

   o  Virginie Galindo (gemalto)

   o  Stefanie Gerdes (Uni Bremen TZI)

   o  Daniel Kahn Gillmor (ACLU)

   o  Wendy M.  Grossman

   o  Christian Grothoff (The GNUnet Project)

   o  Oliver Hahm (INRIA)

   o  Joseph Lorenzo Hall (Center for Democracy & Technology)

   o  Phillip Hallam-Baker

   o  Harry Halpin (W3C/MIT and IRI)

   o  Ted Hardie (Google)

   o  Joe Hildebrand (Cisco Systems)

   o  Russ Housley (Vigil Security, LLC)

   o  Cullen Jennings (CISCO)

   o  Leif Johansson (SUNET)

   o  Harold Johnson (Irdeto)

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   o  Alan Johnston (Avaya)

   o  L.  Aaron Kaplan (

   o  Steve Kent (BBN Technologies)

   o  Achim Klabunde (European Data Protection Supervisor)

   o  Hans Kuhn (NOC)

   o  Christian de Larrinaga

   o  Ben Laurie (Google)

   o  Eliot Lear (Cisco Ssytems)

   o  Barry Leiba (Huawei Technologies)

   o  Sebastian Lekies (SAP AG)

   o  Orit Levin (Microsoft Corporation)

   o  Carlo Von LynX (#youbroketheinternet)

   o  Xavier Marjou (Orange)

   o  Larry Masinter (Adobe)

   o  John Mattsson (Ericsson)

   o  Patrick McManus (Mozilla)

   o  Doug Montgomery (NIST)

   o  Kathleen Moriarty (EMC)

   o  Alec Muffett (Facebook)

   o  Suhas Nandakumar (Cisco Systems)

   o  Linh Nguyen (ERCIM/W3C)

   o  Linus Nordberg (NORDUnet)

   o  Mark Nottingham

   o  Karen O'Donoghue (Internet Society)

Farrell, et al.         Expires November 28, 2015              [Page 31]
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   o  Piers O'Hanlon (Oxford Internet Institute)

   o  Kenny Paterson (Royal Holloway, University of London)

   o  Jon Peterson (Neustar)

   o  Joshua Phillips (University of Birmingham)

   o  Alfredo Pironti (INRIA)

   o  Dana Polatin-Reuben (University of Oxford)

   o  Prof. Johan Pouwelse (Delft University of Technology)

   o  Max Pritikin (Cisco)

   o  Eric Rescorla (Mozilla)

   o  Pete Resnick (Qualcomm Technologies, Inc.)

   o  Tom Ristenpart (University of Wisconsin)

   o  Andrei Robachevsky (Internet Society)

   o  David Rogers (Copper Horse)

   o  Scott Rose (NIST)

   o  Christine Runnegar (Internet Society)

   o  Philippe De Ryck (DistriNet - KU Leuven)

   o  Peter Saint-Andre (&yet)

   o  Runa A.  Sandvik (Center for Democracy and Technology)

   o  Jakob Schlyter

   o  Dr. Jan Seedorf (NEC Laboratories Europe)

   o  Wendy Seltzer (W3C)

   o  Melinda Shore (No Mountain Software)

   o  Dave Thaler (Microsoft)

   o  Brian Trammell (ETH Zurich)

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   o  Hannes Tschofenig (ARM Limited)

   o  Sean Turner (IECA, Inc.)

   o  Matthias Waehlisch (Freie Universitaet Berlin)

   o  Greg Walton (Oxford University)

   o  Rigo Wenning (W3C)

   o  Tara Whalen (Apple Inc.)

   o  Greg Wood (Internet Society)

   o  Jiangshan Yu (University of Birmingham)

   o  Aaron Zauner

   o  Dacheng Zhang (Huawei)

   o  Phil Zimmermann (Silent Circle LLC)

   o  Juan-Carlos Zuniga (InterDigital)

Authors' Addresses

   Stephen Farrell
   Trinity College, Dublin


   Rigo Wenning
   World Wide Web Consortium
   2004, route des Lucioles
   B.P. 93
   Sophia-Antipolis  06902


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   Bert Bos
   World Wide Web Consortium
   2004, route des Lucioles
   B.P. 93
   Sophia-Antipolis  06902

   Email: bert@w3org

   Marc Blanchet
   246 Aberdeen
   Quebec, QC  G1R 2E1


   Hannes Tschofenig
   ARM Ltd.
   110 Fulbourn Rd
   Cambridge  CB1 9NJ
   Great Britain


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