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Network Working Group                                         S. Farrell
Internet-Draft                                   Trinity College, Dublin
Intended status: Informational                                R. Wenning
Expires: October 30, 2014                                         B. Bos
                                                             M. Blanchet
                                                           H. Tschofenig
                                                                ARM Ltd.
                                                          April 28, 2014

                         STRINT workshop report


   The 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.

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 http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on October 30, 2014.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the

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   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) 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  . . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Summary  . . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Workshop goals . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Workshop structure . . . . . . . . . . . . . . . . . . . . . .  5
   5.  Topics . . . . . . . . . . . . . . . . . . . . . . . . . . . .  6
   6.  After the workshop . . . . . . . . . . . . . . . . . . . . . . 20
   7.  IANA considerations  . . . . . . . . . . . . . . . . . . . . . 21
   8.  Security considerations  . . . . . . . . . . . . . . . . . . . 21
   9.  Informative references . . . . . . . . . . . . . . . . . . . . 21
   Appendix A.  Logistics . . . . . . . . . . . . . . . . . . . . . . 24
   Appendix B.  Agenda  . . . . . . . . . . . . . . . . . . . . . . . 25
   Appendix C.  The submitted papers  . . . . . . . . . . . . . . . . 28
   Appendix D.  Workshop chairs & program committee . . . . . . . . . 44
   Appendix E.  Participants  . . . . . . . . . . . . . . . . . . . . 45
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 49

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1.  Context

   [[Editorial note: This version was produced from the minutes, and
   then edited.  It quite likely has some inaccuracies, so the authors
   would welcome corrections from those who attended the workshop.  If
   you're a github person, https://github.com/sftcd/strint-report has
   this so you can contribute there.]]

   The Vancouver IETF plenary concluded [vancouverplenary] 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
   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[I-D.farrell-perpass-attack].

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 (see Appendix C),
   except for a few where authors who couldn't take part in the workshop
   preferred not to publish.

   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.

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   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.  We 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].

   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 (UI) 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.   Ways to better integrate UI issues into the processes of IETF
        and W3C needs further discussion.

   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

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        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 that PM is
   an attack.  [I-D.farrell-perpass-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.

   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. [7]

   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
      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

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   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 which.

5.  Topics

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

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 paricipants felt that standards are needed so that people can
   see if their systems conform to a certain level of security as well
   as easy to remember names 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

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   even prefer a higher cost, for "empire building" reasons).

   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

   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

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   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
   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

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   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 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,
   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 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

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   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
   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?  While 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.

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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
   capablility but otherwise leaves the communication continue in the
   old way.  The detailed definition of OS is now being discussed by the
   IETF security area. [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
   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 then 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

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   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.

   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 UAs 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.

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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
   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 like 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,

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   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., send a
   request via a satellite link and receive the response via a land
   line; or starting a conversation on a cellular link and continuing it
   via wifi.  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
   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
   going through existing protocols to check what data they send that
   isn't really necessary.  One candidate mentioned for such a study was

   _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]

   o  The yearly Workshop on Privacy in the Electronic Society
      (WPES). [12]

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   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.

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.

   But in practice 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: using fake certificates to
   impersonate the endpoints or having access to the private keys of the
   endpoints.  The former is a MITM attack that is difficult to
   distinguish from a more malicious one, 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, but 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

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   the user would rather not have disclosed.

   One widespread example of middleboxes is captive portals, as found on
   the wifi 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 apps, 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.

   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.  Maybe something
   like an extension to DHCP that tells a connecting device about the
   login page can 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 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 relation 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

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   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", how to make the
      existence of traffic and their endpoints stealthy

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.

   Another common case of "false" alarms for MITM (after captive
   portals) is 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

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   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 import 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 MTI, Mandatory To
   Implement and is the current practice for IETF protocols.  [RFC3365]

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

   The question raised at this session was for what protocols on-by-
   default is appropriate, and how to 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.  [[We

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   don't currently have notes from that.]]

5.12.  Break-out 5 - opportunistic

   This break out considered the use of the term "opportunistic" as it
   applies to crytpgraphic security and attempted to progress the work
   towards arriving at an agreed 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

   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 mutal) 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:

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   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 microflow.  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 src 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

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

   e.  If we could fix the reverse SPF check problem, perhaps the source
       could be hidden - but that has assumptions on 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.

   We also discussed the idea of encrypting traffic from CE to CE as
   part of a L3VPN or such.  This could allow hiding of addresses,
   including source, and headers.  From my further conversation with Ron
   Bonica, some customers already do encryption (though not hiding the
   source address) like this.  So, I'm not sure this is very practically
   useful as an enhancement except for encouraging deployment and use.

   Finally, we 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

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   Working groups of the IETF who met 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.
      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.

   (C) Stonehouse Photographic [14]

9.  Informative references

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

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

              (Work in progress.)

              Barnes, R., Schneier, B., Jennings, C., and T. Hardie,
              "Pervasive Attack: A Threat Model and Problem Statement",
              draft-barnes-pervasive-problem-00 (work in progress),
              January 2014.

              Farrell, S. and H. Tschofenig, "Pervasive Monitoring is an
              Attack", draft-farrell-perpass-attack-06 (work in
              progress), February 2014.

              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 2003.

   [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.

   [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,

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              December 2012.

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

              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, <htt

              (Work in progress.)

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

              IETF, "IETF 88 Technical Plenary Minutes", <http://

              Popescu, A., "Geolocation API Specification",
              October 2013, <http://www.w3.org/TR/geolocation-API/>.

   [1]   <http://www.w3.org/>

   [2]   <https://www.iab.org/>

   [3]   <https://www.w3.org/2014/strint/Overview.html>

   [4]   <https://www.ietf.org/meeting/89/index.html>

   [5]   <http://www.strews.eu/>

   [6]   <https://en.wikipedia.org/wiki/Captive_portal>

   [7]   <http://tools.ietf.org/html/bcp72>

   [8]   <https://www.w3.org/2014/strint/papers/44.pdf>

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   [9]   <https://www.w3.org/2014/strint/papers/04.pdf>

   [10]  <http://freehaven.net/anonbib/>

   [11]  <http://www.informatik.uni-trier.de/~Ley/db/conf/pet/

   [12]  <http://www.informatik.uni-trier.de/~Ley/db/conf/wpes/

   [13]  <https://community.qualys.com/blogs/securitylabs/2012/09/14/
         crime  -information-leakage-attack-against-ssltls>

   [14]  <http://www.stonehousephotographic.com/>

   [15]  <http://cordis.europa.eu/fp7/ict/>

   [16]  <http://blog.digital.telefonica.com/>

   [17]  <http://lists.i1b.org/pipermail/strint-attendees-i1b.org/>

   [18]  <https://twitter.com/search?q=%23strint>

   [19]  <http://www.w3.org/2014/02/28-strint-minutes.html>

   [20]  <http://down.dsg.cs.tcd.ie/strint-slides/s0-welcome.pdf>

   [21]  <http://down.dsg.cs.tcd.ie/strint-slides/s1-threat.pdf>

   [22]  <http://down.dsg.cs.tcd.ie/strint-slides/s2-comsec.pdf>

   [23]  <http://down.dsg.cs.tcd.ie/strint-slides/s3-policy.pdf>

   [24]  <http://www.w3.org/2014/03/01-strint-minutes.html>

   [25]  <http://down.dsg.cs.tcd.ie/strint-slides/s4-opportunistic.pdf>

   [26]  <http://down.dsg.cs.tcd.ie/strint-slides/

   [27]  <http://down.dsg.cs.tcd.ie/strint-slides/

   [28]  <http://down.dsg.cs.tcd.ie/strint-slides/

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   [30]  <https://www.w3.org/2014/strint/slides/summary.pdf>

   [31]  <https://strint.pads.ccc.de/1>

   [32]  <https://www.w3.org/2014/strint/papers/01.pdf>

   [33]  <https://www.w3.org/2014/strint/papers/02.pdf>

   [34]  <https://www.w3.org/2014/strint/papers/03.pdf>

   [35]  <https://www.w3.org/2014/strint/papers/05.pdf>

   [36]  <https://www.w3.org/2014/strint/papers/06.pdf>

   [37]  <http://www.internetsociety.org/blog/tech-matters/2014/02/

   [38]  <http://www.circleid.com/posts/

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   [40]  <https://www.w3.org/2014/strint/papers/08.pdf>

   [41]  <https://www.w3.org/2014/strint/papers/09.pdf>

   [42]  <https://www.w3.org/2014/strint/papers/10.pdf>

   [43]  <https://www.w3.org/2014/strint/papers/11.pdf>

   [44]  <https://www.w3.org/2014/strint/papers/12.pdf>

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   [46]  <https://www.w3.org/2014/strint/papers/14.pdf>

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   [54]  <https://www.w3.org/2014/strint/papers/24.pdf>

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   [60]  <https://www.w3.org/2014/strint/papers/31.pdf>

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   [67]  <https://www.w3.org/2014/strint/papers/38.pdf>

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   [69]  <https://www.w3.org/2014/strint/papers/40.pdf>

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   [72]  <https://www.w3.org/2014/strint/papers/43.pdf>

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   [76]  <https://www.w3.org/2014/strint/papers/48.pdf>

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   [77]  <https://www.w3.org/2014/strint/papers/49.pdf>

   [78]  <https://www.w3.org/2014/strint/papers/50.pdf>

   [79]  <https://www.w3.org/2014/strint/papers/51.pdf>

   [80]  <https://www.w3.org/2014/strint/papers/52.pdf>

   [81]  <https://www.w3.org/2014/strint/papers/53.pdf>

   [82]  <https://www.w3.org/2014/strint/papers/54.pdf>

   [83]  <https://www.w3.org/2014/strint/papers/55.pdf>

   [84]  <https://www.w3.org/2014/strint/papers/56.pdf>

   [85]  <https://www.w3.org/2014/strint/papers/57.pdf>

   [86]  <https://www.w3.org/2014/strint/papers/58.pdf>

   [87]  <https://www.w3.org/2014/strint/papers/59.pdf>

   [88]  <https://www.w3.org/2014/strint/papers/60.pdf>

   [89]  <https://www.w3.org/2014/strint/papers/61.pdf>

   [90]  <https://www.w3.org/2014/strint/papers/62.pdf>

   [91]  <https://www.w3.org/2014/strint/papers/63.pdf>

   [92]  <https://www.w3.org/2014/strint/papers/64.pdf>

   [93]  <https://www.w3.org/2014/strint/papers/65.pdf>

   [94]  <https://www.w3.org/2014/strint/papers/66.pdf>

   [95]  <https://www.cs.tcd.ie/Stephen.Farrell/>

   [96]  <http://www.w3.org/People/Rigo/>

   [97]  <http://www.tschofenig.priv.at/wp/?page_id=5>

Appendix A.  Logistics

   The workshop was organised by the STREWS [5] 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

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   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 [4] 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 [17] 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 and are reproduced in this
      report (Appendix C).)

   o  A "Twitter hashtag" (#strint).  Four weeks after the workshop,
      there were still a few new messages [18] about events related to
      workshop topics.

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.

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B.1.  Friday 28 February

   (minutes [19])

   13:00  Registration, Coffee, play with n/w, power, find seat

   14:00  Workshop starts, welcome, logistics, opening/overview
      [slides] [20]

      *  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.

   14:30  I. Threats - What problem are we trying to solve?  (Presenter:
      Richard Barnes; Moderator: Cullen Jennings) [slides] [21]

      *  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)

   15:30  Break

   16:00  II.  COMSEC 1 - How can we increase usage of current COMSEC
      tools?  (Presenter: Hannes Tschofenig; Moderator: Leif Johansson)
      [slides] [22]

      *  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?

   17:30  Break

   17:45  III.  Policy - What policy / legal/ other issues need to be
      taken into account?  (Presenter: Christine Runnegar; Moderator:
      Rigo Wenning) [slides] [23]

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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

   18:30  Session IV - Saturday plan, open-mic, wrap up day

   19:00  Social event

   Break out.
   (C) Stonehouse Photographic [14]

B.2.  Saturday 1 March

   (minutes [24])

   09:00  Welcome again, logistics

   09:15  IV.  COMSEC 2 - What improvements to COMSEC tools are
      needed?(Presenter: Mark Nottingham; Moderator: Steve Bellovin)
      [slides] [25]

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

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

   10:30  Break

   10:45  V. Metadata - How can we reduce the metadata that protocols
      expose?  (Presenter: Alfredo Pironti [slides] [26] / Ted Hardie
      [slides] [27]; Moderator: Alissa Cooper [slides] [28])

      *  Meta-data, fingerprinting, minimisation

      *  What's out there?

      *  How can we do better?

   12:00  Lunch (Buffet)

   13:00  VI.  Deployment - How can we address PM in deployment /
      operations?  (Presenter: Eliot Lear; Moderator: Barry Leiba)
      [slides] [29]

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      *  "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?

   14:30  Break

   15:00  VII. 3 x Break-out Sessions / Bar-Camp style (Hannes

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

      *  Sum up at the end to gather conclusions for report

   15:00  Break-outs:

      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

   16:15  VIII.  Break-out reports, Open mic & Conclusions - What are we
      going to do to address PM? [slides] [30]

      *  Gather conclusions / recommendations / goals from earlier

   17:15  End

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   Whiteboard notes.
   (C) Stonehouse Photographic [14]

Appendix C.  The submitted papers

   [[sort-papers: Group the papers by (rough) topic? --Bert]]

   The following papers were submitted to the workshop.  The abstracts
   were provided by the authors themselves.  (We set up an editable page
   ("Etherpad") [31] where the authors could insert them.)

C.1.  Privacy Protected Email - Phillip Hallam-Baker

   01.pdf [32] - This proposal is two things: First it shows that with
   some small adjustments to S/MIME and PGP we can merge two competing
   end-to-end security proposals that are too hard for people to use
   into one scheme that provides a useful degree of security with no
   thought from the user.  In cases where the user has security concerns
   they can easily determine that they are met.  The second part of the
   proposal is that it the Trust set deployed to secure email encryption
   can be leveraged to solve pretty much every other end-to-end security
   requirement.  If people generate keys for their email we can secure
   chat, video, 2-factor authentication as well.

C.2.  Opportunistic Encryption for MPLS - Stephen Farrell, Adrian

   02.pdf [33] - This is an early proposal for a way to do open-channel
   D-H key agreement and encryption in MPLS.  Two things are maybe
   interesting: a) its an example of trying to add confidentiality to an
   existing protocol with making PM harder as a specific goal and b)
   maybe it shows that there could be a benefit in a generic protocol
   for after-the-fact MITM detection for such cases.  It'd probably be
   most interesting to discuss (a) as one example of something we want
   to do more generally and not the specifics of MPLS at the workshop;
   and I'd be interested in whether or not (b) is tractable (I'm not

C.3.  Overcoming the Friend-or-Foe Paradigm in Secure Communication -
      Sebastian Gajek, Jan Seedorf, Marc Fischlin, Oezguer Dagdalen

   03.pdf [34] - Essentially, our point is that with the existing end-
   to-end client-server security paradigm, e.g. as instantiated in TLS,
   the "good guys" often actually have to mount attacks in order for
   middleboxes (which are on the path between client ans server being
   able) to perform their job.  The good guys are thus technically
   indistinguishable from the bad guys.

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   Concretely, we are proposing to extend TLS in a way that would allow
   authorized modification of certain, dedicated parts of the TLS
   payload by middleboxes, while still allowing for integrity
   verification by clients.  The crypto for such "Interferable Secure
   Communication" exists and we think it is feasible to extend TLS in
   this way in a reasonable timeframe.

C.4.  Flows and Pervasive Monitoring - Ted Hardie

   04.pdf [9] - This document describes methods that may hinder a
   pervasive monitor's efforts to derive metadata from flows.  There are
   three main methods discussed in the paper: aggregation, contraflow,
   and multipath.  These are largely side-effects of other efforts at
   this time, but the paper discusses how they might fit into the design
   space of efforts intended to combat pervasive monitoring and the
   related consequences for network operations.

C.5.  BetterCrypto.org Applied Crypto Hardening - Aaron Zauner, L. Aaron

   05.pdf [35] - BetterCrypto is a community-driven project where
   admins, engineers, cryptographers, security researchers alike
   participate in finding well researched best-practices for commonly
   deployed networked applications and infrastructure.  We try to
   outline a proper interim solution until better protocols and
   standards are widely deployed.  Our hope is that we can contribute to
   a safer internet for all and better understanding of cryptographic
   primitives for the operations community that needs to deploy sound
   security on the public internet.  Our focus group: sysadmins / ops.

C.6.  A Complimentary Analysis (The Danger Of The New Internet Choke
      Points) - Andrei Robachevsky, Christine Runnegar, Karen
      O'Donoghue, Mat Ford

   06.pdf [36] - The ongoing disclosures of pervasive surveillance of
   Internet users' communications and data by national signals
   intelligence agencies have prompted protocol designers, software and
   hardware vendors, as well as Internet service and content providers,
   to re-evaluate prevailing security and privacy threat models and to
   refocus on providing more effective security and confidentiality.  At
   IETF88, there was consensus to address pervasive monitoring as an
   attack and to consider the pervasive attack threat model when
   designing a protocol.  In this paper, we offer a complimentary
   analysis.  We identify some of the components of the Internet
   architecture that provide attractive opportunities for wholesale
   monitoring and/or interception, and, therefore, represent
   architectural vulnerabilities, or choke points.  We also suggest
   possible mitigation strategies and pose some of the questions that

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   need to be considered if the Internet is to evolve to reduce such
   vulnerabilities.  Finally, we identify some significant areas of
   tension or trade-offs, and we consider possible areas for additional
   efforts.  Also: danger-new-internet-choke-points [37] and
   mind_the_step_function [38]

C.7.  Trust Issues with Opportunistic Encryption - Scott Rose, Stephen
      Nightingale, Doug Montgomery

   07.pdf [39] - "Once is happenstance.  Twice is coincidence.  Three
   times is enemy action"

   The lack of authentication in opportunistic encryption could have the
   perverse affect of putting more end users at risk: thinking that they
   are "secure", an end user may divulge private information to an
   imposter instead of the service they believe they have contacted.
   When adding protection mechanisms to protocols, designers and
   implementers should not downplay the importance of authentication in
   order to make opportunistic encryption easier to deploy.  We advocate
   that while opportunistic encryption can solve one set of problems,
   authentication is often desired by end users.

C.8.  Challenges with End-to-End Email Encryption - Jiangshan Yu,
      Vincent Cheval, Mark Ryan

   08.pdf [40] - In this paper we show how the use of an extended
   certificate transparency can build a secure end-to-end email or
   messaging system using PKI without requiring trusted parties nor
   complex p2p key-signing arrangements such as PGP.  This makes end-to-
   end encrypted mail possible, and users do not need to understand or
   concern themselves with keys or certificates.  In addition, we
   briefly present some related concerns i.e. metadata protection, key
   loss mitigation, spam detection, and the security of webmail.

C.9.  Strengthening the path and strengthening the end-points - Xavier
      Marjou, Emile Stephan, Jean-Michel Combes, Iuniana Oprescu

   09.pdf [41] - Internet data is more and more subject to pervasive
   monitoring.  This paper investigates ways of enhancing this situation
   depending on where such pervasive monitoring may occur.  There are
   two different locations to secure: the endpoints and the path between
   these endpoints.  In the present document, we also emphasize the fact
   that encryption, although bringing additional data confidentiality,
   might in some cases contradict security's two other pillars, which
   are availability and integrity.

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C.10.  SIP is Difficult - Jon Peterson

   10.pdf [42] - While SIP is widely used as a protocol for real-time
   communications, it is very difficult to secure from pervasive
   monitoring.  In fact, one could argue that SIP's susceptibility to
   mass surveillance was essential to its success in the marketplace.
   This paper shows why SIP's design left the door open for
   eavesdropping, and what lessons RTCWeb could learn from this.

C.11.  Thoughts of Strengthening Network Devices in the Face of
       Pervasive Surveillance - Dacheng Zhang, Fuyou Miao

   11.pdf [43] - The material released by Edward Snowden has raised
   serious concerns about pervasive surveillance.  People worry that
   their privacy is not properly protected when they are using the
   Internet.  Network product vendors also encounter the doubts on the
   security of their products (e.g., routers, switches, firewalls).
   Such doubts are seriously damaging the Internet ecosystem.  In this
   paper we try to analyze the affects brought by the Snowden scandal on
   our ability to trust products at the core of the Internet and discuss
   what the standard organization can do to help vendors address these
   security concerns.

C.12.  Opportunistic Encryption for HTTP URIs - Mark Nottingham

   12.pdf [44] - This is a proposed method for using TLS with http://
   URIs under discussion in the HTTPbis WG, in particular for HTTP/2 but
   also applicable to HTTP/1.  One of the biggest decisions to make is
   whether or not to require the certs to validate in this scenario.

C.13.  Cyberdefense-Oriented Multilayer Threat Analysis - Yuji Sekiya,
       Daisuke Miyamoto, Hajime Tazaki

   13.pdf [45]

C.14.  A Threat Model for Pervasive Passive Surveillance - Brian
       Trammell, Daniel Borkmann, Christian Huitema

   14.pdf [46] - This document elaborates a threat model for pervasive
   surveillance, assuming an adversary with an interest in
   indiscriminate eavesdropping that can passively observe network
   traffic at every layer at every point in the network between the
   endpoints.  We provide guidelines on evaluating the observability and
   inferability of information and metainformation radiated from
   Internet protocols.  The central message to protocol designers:
   pervasive encryption for confidentiality, protocol and implementation
   design for simplicity and auditability, flexibility to allow
   fingerprinting resistance, and moving away from static identifiers

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   can increase protocol-level resistance to pervasive surveillance.

C.15.  Why Provable Transparency is Useful Against Surveillance - Ben

   15.pdf [47]

C.16.  Withheld

C.17.  Monitoring message size to break privacy - Current issues and
       proposed solutions - Alfredo Pironti

   17.pdf [48] - One of the Internet traffic features that can be easily
   collected by passive pervasive monitoring is the size of the
   exchanged messages, or the total bandwidth used by a conversation.
   Several works have showed that careful analysis of this data can
   break users' expected privacy, even for encrypted traffic.  Despite
   this, little has been done in practice to hide message sizes, perhaps
   because deemed too inefficient or not a realistic threat.

   In this short paper, we contextualize message size analysis in the
   wider pervasive monitoring scenario, which encompasses other powerful
   analysis techniques, and we re-state the severity of the privacy
   breach that message size analysis constitutes.  We finally discuss
   proposals to fix this issue, considering practical aspects such as
   required developer awareness, ease of deployment, efficiency, and
   interaction with other countermeasures.

C.18.  Withheld

C.19.  Making The Internet Secure By Default - Michael H. Behringer, Max
       Pritkin, Steinthor Bjarnason

   19.pdf [49] - Pervasive monitoring on the Internet is enabled by the
   lack of general, fundamental security.  In his presentation at the
   88th IETF Bruce Schneier called for ubiquitous use of security
   technologies to make pervasive monitoring too expensive and thus
   impractical.  However, today security is too operationally expensive,
   and thus only used where strictly required.  In this position paper
   we argue that all network transactions can be secure by default, with
   minimal or no operator involvement.  This requires an autonomic
   approach where all devices in a domain enrol automatically in a trust
   domain.  Once they share a common trust anchor they can secure
   communications between themselves, following a domain policy which is
   by default secure.  The focus of this proposal is the network itself,
   with all protocols between network elements, including control plane
   protocols (e.g., routing protocols) and management plane protocols
   (e.g., SSH, netconf, etc).  The proposal is evolutionary and allows a

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   smooth migration from today's Internet technology, device by device.

C.20.  Increasing HTTP Transport Confidentiality with TLS Based
       Alternate Services - Patrick McManus

   20.pdf [50]

C.21.  Balance - Societal security versus individual liberty - Scott

   21.pdf [51]

C.22.  Strengthening the Extensible Messaging and Presence Protocol
       (XMPP) - Peter Saint-Andre

   22.pdf [52] - This document describes existing and potential future
   efforts at strengthening the Extensible Messaging and Presence
   Protocol (XMPP), for discussion at the W3C/IAB workshop on
   Strengthening the Internet Against Pervasive Monitoring (STRINT).

C.23.  The Internet We Want or the Internet We Deserve? - David Rogers

   23.pdf [53]

C.24.  Beyond Encrypt Everything: Passive Monitoring - Mark Donnelly,
       Sam Hartman

   24.pdf [54]

C.25.  Examining Proxies to Mitigate Pervasive Surveillance - Eliot
       Lear, Barbara Fraser

   25.pdf [55] - The notion of pervasive surveillance assumes that it is
   possible for an attacker to have access to all links and devices
   between end points, as well as end points themselves.  We examine
   this threat is some detail with an eye toward whether trusted
   intermediaries can provide relief from the attack.  We go on to
   examine the costs associated with the various remediation methods.
   In at least one case, we challenge the notion that one should encrypt
   absolutely everything in all cases, as was implied in at least one
   threat analysis.  Finally we summarize in a set of four principles
   that should be considered in future work.

C.26.  Spontaneous Wireless Networking to Counter Pervasive Monitoring -
       Emmanuel Baccelli, Oliver Hahm, Matthias Waehlisch

   26.pdf [56] - Several approaches can be employed to counter pervasive
   monitoring at large scale on the Internet.  One category of

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   approaches aims to harden the current Internet architecture and to
   increase the security of high profile targets (data centers, exchange
   points etc.).  Another category of approaches aims instead for target
   dispersal, i.e. disabling systematic mass surveillance via the
   elimination of existing vantage points, thus forcing surveillance
   efforts to be more specific and personalized.  This paper argues how
   networking approaches that do not rely on central entities - but
   rather on spontaneous interaction, as locally as possible, between
   autonomous peer entities - can help realize target dispersal and thus
   counter pervasive monitoring.

C.27.  Is Opportunistic Encryption the Answer? Practical Benefits and
       Disadvantages - John Mattsson

   27.pdf [57] - In this paper, we give an overview of various
   opportunistic and unauthenticated encryption techniques, and discuss
   their benefits, limits, and disadvantages.  We recommend the Internet
   community to clearly define the term "opportunistic encryption" or to
   use other terms.  We conclude that while opportunistic and
   unauthenticated encryption certainly has its uses and may with the
   right choices provide good enough security for a low cost, general
   deployment of unauthenticated encryption is not an effective way to
   thwart pervasive monitoring.

C.28.  Clearing off the Cloud over the Internet of Things - Carsten
       Bormann, Stefanie Gerdes, Olaf Bergmann

   28.pdf [58] - As was foreshadowed by product introductions in 2013,
   the Consumer Electronics Show 2014 has seen the introduction of a
   large number of "Internet of Things" (IoT) innovations.  Almost all
   of these have in common that they are meant to operate via Cloud-
   based services.  In the light of the recent attention to threats by
   state-level tenacious attackers with significant infrastructure
   (STASI), in particular to their practice of pervasive monitoring, we
   discuss the implications of a cloud-centric IoT landscape, and
   attempt to outline a set of principles as a program to improve the
   long-term outlook.

C.29.  Withheld

C.30.  The Trust-to-Trust Model of Cloud Services - Alissa Cooper,
       Cullen Jennings

   30.pdf [59]

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C.31.  Linkability Considered Harmful - Leif Johansson

   31.pdf [60] - Current debate on pervasive monitoring often focus on
   passive attacks on the protocol and transport layers but even if
   these issues were eliminated through the judicious use of encryption,
   roughly the same information would still be available to an attacker
   who is able to (legally or otherwize) obtain access to linked data
   sets which are being maintained by large content and service

C.32.  Simple Opportunistic Encryption - Andrea Bittau, Michael Hamburg,
       Mark Handley, David Mazieres, Dan Boneh

   32.pdf [61] - Network traffic encryption is becoming a requirement,
   not an option.  Enabling encryption will be a communal effort so a
   solution that gives partial benefits until fully deployed is needed.
   A solution that requires little changes to existing infrastructure
   will also help as it can be quickly deployed to give immediate short-
   term benefits.  We argue that tcpcrypt, a TCP option for
   opportunistic encryption is the path of least-resistance for a
   solution against large-scale traffic encryption.  Tcpcrypt requires
   no changes to applications, is compatible with existing networks
   (works with NATs), and just works by default.  It is high
   performance, so it can be deployed on servers without much concern.
   tcpcrypt attempts to maximize security for any given setting.  By
   default, it will protect against passive eavesdropping, and also
   allows detecting large scale interception.  With authentication,
   tcpcrypt can provide full security against active attackers and so it
   is a complete solution both for the short-term and long-term.

C.33.  An Architecture for a Secure Cloud Collaboration System - Cullen
       Jennings, Suhas Nandakumar

   33.pdf [62] - The Internet technical community is looking at ways to
   address pervasive attacks as described in several other internet
   drafts.  [I-D.barnes-pervasive-problem] describes threat model to
   characterize various pervasive attacks on the Internet
   communications.  There are many systems that need to be secured
   against such attacks but this paper considers one possible way to
   secure cloud based collaborations systems.  At a high level, this
   paper sugests that users or enterprises could run a key server that
   manages the keys to access their content.  The cloud service provider
   would not have access to decrypt the data stored in the cloud but
   various users of the cloud service could get the keys to encrypt and
   decrypt the contents of collaboration sessions facilitated by the
   cloud service.  This does not protect the meta data of who is talking
   to who but can help protect the content of the conversations.

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C.34.  Security and Simplicity - Steven Bellovin

   34.pdf [63]

C.35.  Privacy at the Link Layer - Piers O'Hanlon, Joss Wright, Ian

   35.pdf [64] - This paper gives an overview of the privacy issues
   around the use of link layer identifiers and associated protocols.
   Whilst the IETF generally specifies IP level protocols it does also
   address the link layer in protocols such as address resolution,
   network attachment detection, tunnelling and router redundancy.

   The indiscriminate broadcast of a device's MAC address, a unique and
   effectively personal identifier, allows for unregulated and broad-
   scale tracking of individuals via their personal devices, whether or
   not those devices have made use of a particular service or not.
   These addresses typically remain unchanged for the lifetime of a
   device, creating a persistent, lifelong tracking capability.  The
   collation of such addresses, primarily WiFi and Bluetooth, has been
   been gathering pace and is already in use by organisations such as
   security agencies and advertisers.

   Ephemeral addresses are used further up the stack so why not at the
   link layer?  As default devices should use a randomised MAC address
   and any higher level associations can be maintained as and when
   approved by the user.  Moreover various other 'performance enhancing'
   approaches further degrade the privacy of individuals such as
   proactive discovery of WLAN SSIDs, Detection of Network Attachment
   (DNA), Wireless ISP roaming (WISPr), name lookups and so on.

   All these mechanisms need to be re-examined in the light of pervasive

C.36.  Erosion of the moral authority of middleboxes - Joe Hildebrand

   36.pdf [65] - Many middleboxes on the Internet attempt to add value
   to the connections that traverse that point on the network.  Problems
   in their implementations erode the moral authority that otherwise
   might accrue to the legitimate value that they add.

C.37.  Policy Responses, Implications and Opportunities - Joseph Lorenzo
       Hall & Runa Sandvik

   37.pdf [66] - We raise issues for discussion that lie in the
   interface between policy and technology.  Specifically, we discuss 1)
   routing, processing and data localization policy mandates (i.e., new
   laws that may affect how data flows through the 'net; 2) the

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   uncertain possibility of dilution of credibility of IETF and w3c
   given what we've seen with NIST after NSA-coziness allegations; 3)
   the claim that strenghtening the internet and web will "help the bad
   guys" and the dubious need for "lawful intercept" funcationality; and
   3) abusive content, cryptography as a controlled export technology,
   and the need to standardize more anonymity primitives (onion routing,
   pluggable transport protocols).  We also highlight our own work in
   ensuring that technologists have a voice in policy environments and
   discuss a few interventions we coordinated over the past year,
   focusing on software backdoors and NSA surviellance.

C.38.  Is it time to bring back the hosts file? - Peter Eckersley

   38.pdf [67]

C.39.  Metaphors matter; application-layer; distribute more - Larry

   39.pdf [68] -

   1.  Dont say Attack: IETF should stay away from political theatre:
       changing protocols or workflows not because the change works but
       just to say you did something.  Metaphors matter.

   2.  For most relevant threats, traffic analysis is enough, and
       encyption doesnt mitigate.

   3.  The only deployable protection - if that is what is wanted -
       means shifting architecture from client-server to mesh.

C.40.  Levels of Opportunistic Privacy Protection for Messaging-Oriented
       Architectures - Dave Crocker, Pete Resnick

   40.pdf [69] - Messaging protection against pervasive monitoring (PM)
   needs to cover primary payload, descriptive meta-data, and traffic-
   related analysis.  Complete protection against PM, for traffic
   through complex handling sequences, has not yet been achieved
   reliably in real-world operation.  Consequently, this document
   considers a range of end-to-end, object-based mechanisms, distinct
   from channel-based mechanisms.  Each approach offers incremental
   protection levels that can be provided with existing, or low-risk,
   component technologies, such as through the DNS and MIME conventions.

C.41.  Fingerprinting Guidance for Web Specification Authors - Nick Doty

   41.pdf [70] - http://w3c.github.io/fingerprinting-guidance/ -
   Exposure of settings and characteristics of browsers can impact user
   privacy by allowing for browser fingerprinting.  This document

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   defines different types of fingerprinting, considers distinct levels
   of mitigation for the related privacy risks and provides guidance for
   Web specification authors on how to balance these concerns when
   designing new Web features.

C.42.  Eradicating Bearer Tokens for Session Management -  Philippe De
       Ryck, Lieven Desmet, Frank Piessens, Wouter Joosen

   42.pdf [71] - Session management is a crucial component in every
   modern web application.  It links multiple requests and temporary
   stateful information together, enabling a rich and interactive user
   experience.  The de facto cookie-based session management mechanism
   is however flawed by design, enabling the theft of the session cookie
   through simple eavesdropping or script injection attacks.  Possession
   of the session cookie gives an adversary full control the user's
   sover ession, allowing him to impersonate the user to the target
   application and perform transactions in the user's name.  While
   several alternatives for secure session management exist, they fail
   to be adopted due to the introduction of additional roundtrips and
   overhead, as well as incompatibility with current Web technologies,
   such as third-party authentication providers, or widely deployed
   middleboxes, such as web caches.  We identify four key objectives for
   a secure session management mechanism, aiming to be compatible with
   the current and future Web. We propose SecSess, a lightweight session
   management mechanism based on a shared secret between client and
   server, used to authenticate each request.  SecSess ensures that a
   session remains under control of the parties that established it, and
   only introduces limited overhead.  During session establishment,
   SecSess introduces no additional roundtrips and only adds 4.3
   milliseconds to client-side and server-side processing.  Once a
   session is established, the overhead becomes negligible (<0.1ms), and
   the average size of the request headers is even smaller than with
   common session cookies.  Additionally, SecSess works well with
   currently deployed systems, such as web caches and third-party
   services.  SecSess also supports a gradual migration path, while
   remaining compatible with currently existing applications.

C.43.  STREWS Web-platform security guide: security assessment of the
       Web ecosystem - Martin Johns, Lieven Desmet

   43.pdf [72] - In this document, we report on the Web-platform
   security guide, which has been developed within the EC-FP7 project
   STREWS.  Based on their research, the STREWS consortium argues that
   in order to strengthening the Internet (e.g. against pervasive
   monitoring), it is crucial to also strengthen the web application
   ecosystem, the de-facto Internet application platform.

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C.44.  Pervasive Attack: A Threat Model and Problem Statement - Richard
       Barnes, Bruce Schneier, Cullen Jennings, Ted Hardie

   44.pdf [8] - Documents published in 2013 have revealed several
   classes of "pervasive" attack on Internet communications.  In this
   document, we review the main attacks that have been published, and
   develop a threat model that describes these pervasive attacks.  Based
   on this threat model, we discuss the techniques that can be employed
   in Internet protocol design to increase the protocols robustness to
   pervasive attacks.

C.45.  Cryptech - Building a More Assured HSM with a More Assured Tool-
       Chain - Randy Bush

   45.pdf [73]

C.46.  Replacing passwords on the Internet AKA post-Snowden
       Opportunistic Encryption - Ben Laurie, Ian Goldberg

   46.pdf [74]

C.47.  End-User Concerns about Pervasive Internet Monitoring: Principles
       and Practice - Tara Whalen, Stuart Cheshire, David Singer

   47.pdf [75] - This position paper will discuss pervasive monitoring
   on the Internet from the perspective of end users: what are
   overarching concerns around pervasive monitoring, and what are some
   steps that could be taken to address those concerns?  We begin by
   exploring a preliminary set of characteristics of systemic
   surveillance, which can be used to pinpoint dominant concerns of end
   users that should be addressed through technical means.  We then
   illustrate one specific significant problem facing end users, namely
   that of certificate errors, which can be exploited to facilitate
   pervasive surveillance.  We suggest that users should not be required
   to determine whether a certificate error is valid, but instead to
   block access to websites that generate such errors.  We believe this
   approach would be more effective in protecting end users in an
   environment of persistent network threats.

C.48.  Developer-Resistant Cryptography - Kelsey Cairns, Graham Steel

   48.pdf [76] - "Properly implemented strong crypto systems are one of
   the few things that you can rely on" - Edward Snowden.  So why is
   mass surveillance so successful?  One (big) problem is endpoint
   security.  Another is that strong crypto systems are sufficiently
   difficult to implement that often either mistakes are made resulting
   in catastrophic loss of security, or cryptography is not used at all.
   What can we do to make cryptography easier to use and more resistant

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   to developer errors?

C.49.  Improving the reliability of key ownership assertions - Kai

   49.pdf [77] - A majority of today's secure Internet connections rely
   on Certificate Authorities not being abused for issueing false
   certificates (key ownership assertions), which might get abused for
   interception purposes, despite the risk of detection.  I suggest to
   enhance Internet protocols with protective mechanisms to detect false
   key ownership assertions.  Ideas: (1) Using a network of proxy
   services, for example as implemented by the The Onion Router (Tor),
   consistency checking chould be performed by individual clients, in
   order to detect assertions that are likely false, prior to allowing a
   connection (see Detector.io). (2) Extend the idea that notary
   services provide a second opinion about the correctness of key
   ownership assertions, by requiring CAs to run such services (kuix.de/
   mecai). (3) Implement protocol extensions, where client software
   reports previously seen key ownership assertions to the operators of
   services, allowing the discovery of false ownership assertions.

C.50.  Mike O'Neill's Position Paper - Mike O'Neill

   50.pdf [78]

C.51.  Detecting MITM Attacks on Ephemeral Diffie-Hellman without
       Relying on a PKI in Real-Time Communications - Alan Johnston

   51.pdf [79] - With the recent revelations about pervasive
   surveillance on the Internet, there is renewed interest in techniques
   that protect against passive eavesdropping without relying on a
   Public Key Infrastructure (PKI).  An ephemeral Diffie-Hellman (DH)
   key agreement can provide such protection, but (without
   authentication) the exchange is vulnerable to a Man in the Middle
   (MitM) attack.  An example of a protocol that has MitM protection for
   a DH key agreement is ZRTP, RFC 6189, "ZRTP: Media Path Key Agreement
   for Unicast Secure RTP."  ZRTP provides pervasive surveillance
   resistant security for Voice over IP (VoIP), video communication, and
   other real-time communication services.  This paper describes the
   techniques used by ZRTP to detect MitM attacks, and explores whether
   these techniques could be used to develop a general MitM detection
   protocol to be used by other non-real-time communication protocols.
   An example of how ZRTP can provide MitM detection for another
   protocol, DTLS-SRTP, Datagram Transport Layer Security - Secure Real-
   time Transport Protocol, is given.

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C.52.  Trust & Usability on the Web, a Social/Legal perspective - Rigo
       Wenning, Bert Bos

   52.pdf [80] - (1) The browsers' UIs for security are very technical
   and seem to avoid saying anything useful, maybe so that the browsers
   and CAs cannot be held responsible. (2) A user wanting to configure
   security has difficulty finding the UI and then often discovers that
   settings are hard-coded or unclear. (3) The security model is based
   on trusting a few commercial entities and mistrusting the user, who
   ends up without control over his software if one of those entities is
   compromised or doesn't share his goals.  Conclusion: We need better
   UIs, which in turn requires a PKI that has the metadata and social
   aspects that help users understand and explore the keys and the
   organizations behind them.

C.53.  Hardening Operations and Management Against Passive Eavesdropping
       - Bernard Aboba

   53.pdf [81] - Today within service providers protocols used for
   operations and management frequently send data in the clear, enabling
   the data to be collected by passive eavesdroppers.  Examples of
   operations and management protocols include Authentication,
   Authorization and Accounting (AAA), syslog and Simple Networking
   Monitoring Protocol (SNMP).  Since the publication of "Operational
   Security Current Practices in Internet Service Provider Environments"
   [RFC4778], the IETF has developed specifications that enable per-
   packet confidentiality to be applied to operations and management
   protocols.  By developing updated operational guidance recommending
   deployment of per-packet confidentiality based on recent IETF Request
   for Comments (RFCs) and work-in-progress, the IETF can assist in
   bringing customer and regulatory pressure to bear in improving
   operational practices.

C.54.  A few theses regarding privacy and security - Andreas Kuckartz

   54.pdf [82]

C.55.  Meet the new threat model, same as the old threat model - Eric

   55.pdf [83] - The Internet environment has a fairly well understood
   threat model.  In general, we assume that the end-systems engaging in
   a protocol exchange have not themselves been compromised.  Protecting
   against an attack when one of the end-systems has been compromised is
   extraordinarily difficult.  It is, however, possible to design
   protocols which minimize the extent of the damage done under these

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   By contrast, we assume that the attacker has nearly complete control
   of the communications channel over which the end-systems communicate.
   This means that the attacker can read any PDU (Protocol Data Unit) on
   the network and undetectably remove, change, or inject forged packets
   onto the wire.  This includes being able to generate packets that
   appear to be from a trusted machine.  Thus, even if the end-system
   with which you wish to communicate is itself secure, the Internet
   environment provides no assurance that packets which claim to be from
   that system in fact are. - [RFC3552]

C.56.  It's Time for Application-Centric Security - Yuan Gu, Harold

   56.pdf [84] - An 'application' is an organized data/executable-code
   compound performing a specific function or service.  We hold that
   applications should be protected intrinsically (by obfuscated,
   tamper-resistant code and data), as well as extrinsically (by
   encrypted communication, hardened hardware platforms, authenticated
   access). (1) Cloud-based applications are vulnerable to their hosting
   services or neighbors. (2) Peripheral-based applications (on phones,
   pads, PDAs, or more generally in the Internet of Things) are
   vulnerable because hardware security is inconsistent and very
   expensive to repair. (3) Browser-based applications are vulnerable
   because they run on potentially hostile or malware-infected browsers
   or platforms which we don't control.  Application obfuscations such
   as homomorphic transforms on data and computation (motto: avoid data
   or computation in plain form) and increased interdependency (motto:
   aggressive fragility under tampering) can effectively address these

C.57.  Sabatini Monatesti position paper - Sabatine Monatesti

   57.pdf [85]

C.58.  Trust problems in pervasive monitoring - Melinda Shore, Karen

   58.pdf [86]

C.59.  Beyond "Just TLS Everywhere": From Client-encrypted Messaging to
       Defending the Social Graph - Harry Halpin, George Danezis

   59.pdf [87]

C.60.  Network Security as a Public Good - Wendy Seltzer

   60.pdf [88] - Network security depends on cooperation of multiple
   actors in the Internet ecosystem.  Standards consortia should support

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   and help coordinate activity to protect the commons.

C.61.  Statement of Interest on behalf of the W3C TAG - Dan Appelquist

   61.pdf [89]

C.62.  Improving Security on the Internet - Hannes Tschofenig

   62.pdf [90] - Securing the Internet has been an on-going activity
   since the early days of the IETF and a variety of technical
   specifications have been standardized.  Someone reading through IETF
   RFCs might easily get the impression that the Internet should be very
   secure.  This is, however, not the entire story as the never-ending
   series of breaches and recently the Snowden revelations have
   illustrated.  While on paper everything looks pretty good many
   problems can be found in implementations and with deployments.

   In this position paper the author makes the argument that improving
   the collaboration between different communities in the Internet
   software development life-cycle will be crucial for improving
   security on the Internet.

C.63.  Protecting customer data from government snooping - Orit Levin

   63.pdf [91]

C.64.  Privacy Aware Internet Development Initiative 2014 - Achim

   64.pdf [92] - Protecting privacy on the Internet requires more than
   using encryption.  Protocols, implementations and applications must
   minimise the amount of personal data that is distributed and
   collected.  Work is required to develop and disseminate privacy aware
   design and impmementation techniques to the actual developers.  The
   paper is a call for interest for an initiative aiming to address this
   need, supported by privacy and technology experts.

C.65.  The Internet is Broken: Idealistic Ideas for Building a NEWGNU
       Network - Christian Grothoff, Bartlomiej Polot, Carlo von Loesch

   65.pdf [93] - This paper describes issues for security and privacy at
   all layers of the Internet stack and proposes radical changes to the
   architecture to build a network that offers strong security and
   privacy by default.

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C.66.  Opportunistic Keying as a Countermeasure to Pervasive Monitoring
       - Stephen Kent

   66.pdf [94] - This document was prepared as part of the IETF response
   to concerns about "pervasive monitoring" as articulated in
   [draft-farrell-perpass-attack].  It begins by exploring terminology
   that has been used in IETF standards (and in academic publications)
   to describe encryption and key management techniques, with a focus on
   authentication vs. anonymity.  Based on this analysis, it propose a
   new term, "opportunistic keying" (OK) to describe a goal for IETF
   security protocols, one possible countermeasure to pervasive
   monitoring.  It reviews key management mechanisms used in IETF
   security protocol standards, with respect to these properties, to
   identify what changes might be needed to offer OK with minimal
   changes.  The document ends by examining possible impediments to and
   potential adverse effects associated with deployment and use of
   techniques that would increase the use of encryption, even when keys
   are distributed in an unauthenticated manner.

Appendix D.  Workshop chairs & program committee

   The workshop chairs were three: Stephen Farrell [95] (TCD) and Rigo
   Wenning [96] (W3C) from the STREWS project, and Hannes
   Tschofenig [97] (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 E.  Participants

   The participants to the workshop were:

   o  *Bernard Aboba* (Microsoft Corporation)

   o  *Thijs Alkemade* (Adium)

   o  *Daniel Appelquist* (Telefonica Digital)

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   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)

   o  *Mark Donnelly* (Painless Security)

   o  *Nick Doty* (W3C)

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   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)

   o  *Alan Johnston* (Avaya)

   o  *L. Aaron Kaplan* (CERT.at)

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   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)

   o  *Piers O'Hanlon* (Oxford Internet Institute)

   o  *Kenny Paterson* (Royal Holloway, University of London)

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   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* (&#12461;&#12524;&#12452;)

   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)

   o  *Hannes Tschofenig* (ARM Limited)

   o  *Sean Turner* (IECA, Inc.)

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   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

   Email: stephen.farrell@cs.tcd.ie

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

   Email: rigo@w3.org

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

   Email: bert@w3org

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   Marc Blanchet
   246 Aberdeen
   Quebec, QC  G1R 2E1

   Email: Marc.Blanchet@viagenie.ca
   URI:   http://viagenie.ca

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

   Email: Hannes.tschofenig@gmx.net
   URI:   http://www.tschofenig.priv.at

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