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Internet Engineering Task Force                         J. Pouwelse, Ed.
Internet-Draft                            Delft University of Technology
Intended status: Standards Track                        October 22, 2012
Expires: April 25, 2013

            Media without censorship (CensorFree) scenarios


   This document describes some scenarios in which one can imagine that
   the ability of authoritarian regime to censor news dissemination is
   reduced.  It tries to draw some conclusions about what's desirable
   and what's not acceptable for users in those scenarios.

   The CensorFree objective is to standardize the protocols for
   microblogging on smartphones with a focus on security and censorship
   resistance.  Microblog entries are short text messages, possibly
   enriched with pictures or streaming video.  The goal is to devise
   protocols which guard against all known forms of censorship such as:
   cyberspace sabotage, digital eavesdropping, infiltration, fraud,
   Internet kill switches and lawyer-based attacks with the best known
   protective methods.

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
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   This Internet-Draft will expire on April 25, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal

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   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents

   1.  Requirements Language  . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Goal: microblogging  . . . . . . . . . . . . . . . . . . . . .  4
   4.  Driving scenarios  . . . . . . . . . . . . . . . . . . . . . .  5
     4.1.  20sec scenario . . . . . . . . . . . . . . . . . . . . . .  6
       4.1.1.  Adversary model: A simplistic attacker . . . . . . . .  6
       4.1.2.  Scenario details and architectural requirements  . . .  6
     4.2.  Kill-switch scenario . . . . . . . . . . . . . . . . . . .  8
       4.2.1.  Adversary model: An advanced attacker  . . . . . . . .  8
       4.2.2.  Scenario details and architectural requirements  . . .  8
     4.3.  friend-to-friend scenario  . . . . . . . . . . . . . . . .  9
       4.3.1.  Adversary model: A powerful attacker . . . . . . . . .  9
       4.3.2.  Scenario details and architectural requirements  . . . 10
     4.4.  Transmorph ability . . . . . . . . . . . . . . . . . . . . 10
     4.5.  A single global conversation . . . . . . . . . . . . . . . 11
     4.6.  Spammers and hoaxes  . . . . . . . . . . . . . . . . . . . 11
   5.  Design principles: simplicity and prior success  . . . . . . . 12
   6.  Background rant: lack of coordination and fragmentation  . . . 12
   7.  Current running code and related work  . . . . . . . . . . . . 13
   8.  Open issues  . . . . . . . . . . . . . . . . . . . . . . . . . 14
     8.1.  Use cases and threat model . . . . . . . . . . . . . . . . 15
     8.2.  System components, definitions and system architecture . . 15
     8.3.  Current technology and gap . . . . . . . . . . . . . . . . 15
     8.4.  Detailed system design and protocol specification  . . . . 15
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 15
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 15
     11.2. Informative References . . . . . . . . . . . . . . . . . . 15
     11.3. URL References . . . . . . . . . . . . . . . . . . . . . . 15

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1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  Introduction

   Bits moving across the Internet are vulnerable to surveillance and
   censorship on an unprecedented scale.  Today, both Internet providers
   and governments possess the ability to monitor the moves of their
   digital citizens from central infrastructure points.  This monitor
   ability creates significant potential for abuse, and a threat that
   goes beyond the scope of mere monitoring or filtering.

   Governments have demonstrated their ability to disable communications
   networks in times of crisis.  During the 2011 Arab Spring, Egyptian
   authorities demanded that telecommunication companies sever their
   broadband connections and mobile networks--both local and European
   operators were forced to comply, and, as a result, digital Egypt
   vanished.  Despite the country's decentralized infrastructure, an
   Internet blackout was relatively easy to carry out.  The roles and
   consequences of social media (e.g., Facebook and Twitter) during that
   same period further illustrate the capacity governments have for
   Internet censorship and the challenges activists face in combating
   it.  The April 6 Youth Movement from Egypt committed digital dissent
   in full public view.  According to The New York Times[YOUTH], the
   movement "provided a structure for a new generation of Egyptians, who
   aren't part of the nation's small coterie of activists and opinion
   makers, to assemble virtually and communicate freely about their
   grievances."  But moving protest organizations to social media
   accessible to the public-at-large can hold surprising risks.  On the
   ground, the movement's organization of labor strikes and protests in
   Facebook groups, many with thousands of followers, triggered arrest
   and imprisonment.  Protesters in other countries quickly took note of
   Egypt's lesson and disabled their public Facebook profiles.  In
   response, one government initiated social media searches on incoming,
   young, plane travelers by forcing them to login to Facebook upon
   arrival, thereby revealing online activities and any anti-government

   A glimmer of hope exists.  The Arab Spring shows that a new
   generation is claiming their right to express themselves.
   Microblogging, social media in general and traditional satellite news
   broadcast networks are perceived as critical catalysts for political
   change.  Generic computational fabric is soon getting in the hands of
   two billion people with the growth of smartphones and increasingly
   affordable communication.  These smartphones are increasingly used to

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   record and spread disruptive audiovisual material, even in regions
   without media freedom.

   Democratic countries also face a dilemma.  Restrictions on the free
   information flow is the topics of several proposed laws by elected
   representatives.  The strength of copyright law impacts digital
   information flow.  Politicians must decide between weak copyright
   law, as championed by civil rights activists versus strong copyright
   enforcement, as promoted by numerous players in the creative
   industries.  Recent furor around SOPA, PIPA, etc. in the US plus the
   European Parliament vote on ACTA is highly relevant in this context.

   The uniqueness of The Internet lies in the IETF standards.  Moving
   certain bits to certain locations or offering a service requires no
   prior official approval.  However, Internet-deployed mechanisms now
   exist which filter news and media in general for both surveillance
   and censorship.  The Internet has ceased to provide reliable
   transport service for all users.  The IETF can repeat it's historical
   inter-networking role again by setting the standard for reliable flow
   of packets of news.

3.  Goal: microblogging

   The goal is creating a microblogging standard and facilitating a
   reference implementation for portable devices which is capable of
   operating in a hostile environment.  This standard should be
   resilient against a government Internet kill switch.  Microblogging
   is an increasingly popular technology for lightweight interaction
   over the Internet.  It differs from traditional blogging in that

   o  Posts are short (typically less than 140 characters, which is the
      limit in SMS).

   o  Posts are in plain text.

   o  People can reply to your posts, but not directly comment on them.

   o  People learn about your posts only if they have permission to view

   o  Your microblogging feed is discovered based on your identity at a
      domain or with a service.

   This proposed draft standard SHALL provide: "information
   dissemination from a single smartphone to an audience of millions in
   the form of microblogging, enriched with pictures or streaming video
   which is guarded against all known forms of censorship such as:

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   cyberspace sabotage, digital eavesdropping, infiltration, fraud,
   Internet kill switches and lawyer-based attacks with the best known
   protective methods".

   The focus on microblogging is driven by feasibility.  Creating a
   standard for overcoming censorship for social networks, search
   engines or web browsing in general is extremely challenging.
   Mitigating the threats posed by Internet kill switches requires focus
   on the most feasible viable standard.  The related work listed in
   this document shows existing operational systems.  Existing systems
   cover all functionality we desire, however none of them cover all
   aspects and little interoperability exists.

   As early as 2006, long before Arab spring events, it was reported
   that individuals in wide swathes of the Arab world were using
   Bluetooth technology to bypass police restrictions.  According to
   news reports[DATING], communication between men and women in this
   region had been made possible by cellphone technology.  When
   Bluetooth-capable phones are in close proximity, they can engage
   directly in digital and social chatter--no other infrastructure is
   needed.  Moreover, when sharing photos or bandwidth-hungry videos
   with friends it also pays to be close.  Government provided cellphone
   networks might not be filtering you, but can still be dreadfully
   slow.  It therefore pays to use cell phones' Bluetooth-based, direct
   file-transfer features--and it comes as no surprise that wireless-
   transfer apps have seen millions of installs.  A query of Google
   Trends for the phrase "Bluetooth transfer" reveals a geographical
   spread of this interesting social phenomenon[TREND].  It seems
   millions of mobile phone owners are already employing the social
   practice of wireless data exchange.  Viability is increased by
   building upon this practice.

4.  Driving scenarios

   Recent Arab spring events have shown the power of ubiquitous camera-
   phones, new media and microblogging.  This document proposes to uses
   smartphones, wifi and USB sticks for multimedia transport and
   playback.  The architecture, features and driving scenarios are
   specifically crafted to enable compliant implementations as a single
   smartphone app without any additional server infrastructure.

   Each scenario is focused on certain threats in a hostile environment.
   The adversary becomes stronger in several of the following scenarios
   and we also focus on the social media context.

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4.1.  20sec scenario

   First scenario, called "20sec", defines an open microblogging
   standard.  This first scenario duplicates existing microblogging
   practices with an open standard in a fully decentralized setting.
   The scenario requirements are performance equal to central-server
   based approach (e.g. the ability to reach 20 million people in 20

4.1.1.  Adversary model: A simplistic attacker

   Eavesdropping is a common and easy passive attack in a hostile
   environment.  In this scenario we assume the attacker has full access
   to the network between the user and any Internet server.
   Specifically, the adversary can observe, block, delay, replay and
   modify all traffic coming from any server.  Furthermore, all servers
   such as DNS servers, web servers, swarm trackers, CDN cloud servers
   and access portals are assumed to be under direct or indirect control
   of the adversary.

   The adversary cannot compromise traffic between smartphones or other
   participating devices.  The adversary cannot compromise smartphones
   or other participating devices.  The adversary cannot break standard
   cryptographic primitives, such as block ciphers and message-
   authentication codes.

4.1.2.  Scenario details and architectural requirements

   Smartphone owner Alice with wifi-based Internet access records an eye
   witness video.  She attaches this video to a microblog entry and
   shares this story plus video automatically with friends Bob and
   Charlie which are subscribed to her news feed.  Alice does not need
   to trust any central server with her credentials or has to prove her
   identity to a central (web) server.  Bob and Charlie are both behind
   a NAT middlebox compliant to the BEHAVE recommendations [RFC4787].
   No assistance of a coordinating server (e.g.  STUN or TURN) is
   required to traverse this NAT box using UDP messages.  This scenario
   assumes direct or NAT-based Internet access (the next scenario deals
   with packet forwarding).

   Performance should be equal to central-server based approach,
   providing the ability to reach 20 million people in 20 seconds.  This
   first scenario duplicates existing microblogging practices with an
   open standard in a fully decentralized setting.  The 20sec scenario
   requires that solutions provide seamless backwards compatibility with
   existing leading solutions (e.g.  Twitter, Sina Weibo, chyrp, heello)
   by using content import tools.  Proposed open solutions MUST permit
   easy bulk trans-coding and ingest of existing news feeds into this

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   open standard.

   An essential feature of the 20sec scenario is all central gatekeepers
   or communication to them is possibly compromised.  Ownership of data
   is fundamental to autonomy.  To meet the anti-censorship goal, 20sec
   assumes an infrastructure which is not dependent and completely
   decoupled from potentially hostile servers such as DNS servers and
   web servers. 20sec MUST be based on full self-organization.  The
   infrastructure consists purely of devices running compliant
   implementations.  No central server requires installation or
   maintenance, making this infrastructure independent on any type of
   funding or business model. 20sec requires an overlay which is highly
   resilient.  Smartphones, tablets and PCs are able to utilize this P2P
   overlay for microblogging.  Existing solutions such as [OPENMICRO]
   require a central webserver and OAuth-like authentication primitives.
   This prior work is not suitable for our 20sec scenario, as we aim to
   remove all server, ultrapeer or superpeer reliance and equality of
   all participants in the overlay.

   When Alice downloads her smartphone app and starts it for the first
   time it needs to bootstrap.  On this initial startup, the
   microblogging software must bootstrap and find at least one other
   peer in the overlay.  The most simple method of bootstrapping is
   using a list of currently online peers plus their port number.  See
   the example below.

   # file: Central-Bootstrap-Servers.txt
   # default bootstrap peers
   server1.always-online.org 6420
   host1.never-offline.ro 6420
   sealand.routed.org 6420 6420

   A file sharing program needs a fresh list of peers to bootstrap.
   Thus a pre-defined list of peers is included in the software
   installer.  As peers can go offline it is important that at least one
   peer out of possibly thousands on the list is still online.  This
   pre-existing address list of possibly working peers must therefore
   remain valid for as long as possible.  Bootstrapping is done by
   contacting peers in the list, possibly in parallel.  If a single
   peers replies, the smartphone app of Alice is connected.  Once
   connected, a fresh list of working peer Internet addresses COULD be
   requested.  Several ideas have been proposed on bootstrapping systems
   without an "online bootstrap server" list.  For instance, simply by
   smart brute force pinging, as described by the University of Denver

   It is RECOMMENDED compliant implementations explore and implement

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   efficient alternatives for decentralized initial bootstrapping.

4.2.  Kill-switch scenario

   This scenario describes a situation without any Internet access.  We
   assume the government has essentially "killed" the Internet, in an
   Arab spring like scenario.  It is focused on ad-hoc packet forwarding
   between smartphones.

4.2.1.  Adversary model: An advanced attacker

   The adversary has disabled all Internet-based communication.

   We assume the adversary cannot eavesdrop, jam, delay, replay, modify
   or spoof wireless communication between smartphones.  The adversary
   cannot compromise smartphones or other participating devices.  The
   adversary cannot break standard cryptographic primitives, such as
   block ciphers and message-authentication codes.

4.2.2.  Scenario details and architectural requirements

   Smartphone owner Alice has no Internet access.  She records a video,
   attaches this video to a microblog entry in her phone app.  Friends
   Bob and Charlie are subscribed to her news feed.  Bob and Charlie are
   at some point within range of the wifi, bluetooth or other wireless
   capability of Alice.  This fresh microblog entry plus video is shared
   automatically.  Bob obtained the message from Alice using a
   smartphone app which is periodically scanning if other devices are
   around and if they possibly have fresh news.  This periodic
   synchronization SHOULD be energy-efficient.  Bob sees no noticeable
   decrease in battery lifetime after he obtained unconstrained news
   access.  Charlie later goes to a square where numerous people have
   gathered, most of which are highly interested in the latest videos.
   The fresh messages automatically spreads in this crowd.

   Note that this scenario differs from Delay-Tolerant Networking (DTN),
   as being investigated by a Working Group within the Internet Research
   Task Force [RFC4838] and scientists[BUBBLE].  The DTN focus is on
   finding routes to an explicitly given destination, usually by
   maintaining routing tables.  Their system model and terminology
   cannot be applied in our context, for instance, "Endpoint
   Identifiers" which identify the original sender and final
   destination.  In our Internet-Free scenario sender Alice does NOT
   explicitly send a message with destination Bob.

   A wealth of related work exists in this area.  General solutions are
   found in mobile ad hoc networks (MANET), which provide self-organized
   IP routing among wireless devices, and delay-tolerant networks (DTN),

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   which use a simple store-and-forward primitive to communicate over
   heterogeneous links.  Mobile ad hoc networks have been studied within
   the Internet Research Task Force (IRTF) since 1997, leading to
   several standards published by the IETF's MANET Working Group, while
   delay-tolerant networks are currently the focus of the IRTF's DTN
   Research Group.  We hope that much of that knowledge can be reused,
   despite our scenario differing slightly from DTN (as being
   investigated by the IRTF [RFC4838])

4.3.  friend-to-friend scenario

   This third scenario uses friend-to-friend networking to remove the
   requirement for active networking and wifi sensing.  The smartphones
   of Alice and Bob need to be synced manually.  This scenario SHOULD
   deliver a privacy-by-design type of microblogging service.

4.3.1.  Adversary model: A powerful attacker

   We must assume from the Arab Spring scenario the existence of a
   powerful adversary.  For instance, the adversary has disabled all
   Internet-based communication.  The adversary even actively monitors
   wireless communication.  Protocol designers have identified the
   following threats [BRIAR] for similar circumstances:

   o  The adversary can observe, block, delay, replay, and modify
      traffic on the underlying network.  Thus, the microblogging
      service must ensure end-to-end security without relying on the
      security of the underlying network.

   o  Wireless communication is regularly monitored.  Responding to any
      wireless requests from a stranger is a direct threat to the user
      and extremely harmful.

   o  Possession of encrypted electronic messages or encryption
      technology in general is extremely harmful to the smartphone

   o  The adversary has a limited ability to compromise smartphones or
      other participating devices.  If a device is compromised, the
      adversary can access any information held in the device's volatile
      memory or persistent storage.

   o  The adversary can choose the data written to the microblogging
      layer by higher protocol layers.

   o  The adversary cannot break standard cryptographic primitives, such
      as block ciphers and message-authentication codes.

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   Encryption is not a sufficient requirement of the friend-to-friend
   scenario, everything MUST be hidden.  Possession of smartphones apps
   with encryption is already dangerous for the owner.

4.3.2.  Scenario details and architectural requirements

   Reports from repressive regions indicate that USB sticks are commonly
   used to transport sensitive information.  See for instance this
   extensive report on North-Korea [NKOREA].  In the friend-to-friend
   scenario a network of friends is trusted to transport news manually,
   by simply carrying it around.  Smartphones with NFC capability or
   manual USB transfer are used to duplicate and move messages.  Thus
   Alice delivers her fresh news message to Bob, which is later given
   manually to Charlie.

   As direct social connections are sparse and proximity of friends is
   not continuous, this scenario SHOULD facilitate usage of friends-of-
   friends or further removed social ties to relay news messages.  This
   requires the development of a decentralized social network, for
   instance, with digital signatures of friendship certificates.  In
   effect this would create a "decentralized social network", completely
   autonomous and owned by all participants.  We assume Alice only has
   Bob in her friendlist and Bob only has Charlie in his friendlist.  An
   OPTIONAL feature is that the smartphone apps running on the
   smartphone Alice and Charlie detect that they have friendship path
   through Bob. Fresh news is thus exchanged.

   The interception of a single smartphone MUST NOT expose the app
   itself, any friend list or worst: the entire social network.  We
   assume Alice is placing herself in danger with electronic tools for
   "subversive activities against the democratic republic".  Information
   hiding techniques are essential or even life-critical.  Possibly
   based on Zero-Knowledge Proof (ZKP) protocols [ZEROKNOW].  The
   smartphone app MUST pose as a harmless entertainment feature of a
   smartphone or use another mechanism to become a "stealth app".

   This scenario requires modification and enhancement based on real-
   world experience from human rights activist [EGYPTSTUDY].

4.4.  Transmorph ability

   Prior scenarios expanded the threat model.  This and the following
   scenarios are focused on the social media context.  News is created
   in a region without freedom and then needs to travel to the outside
   world.  We refer to this simply as the freedom/non-freedom border.
   Different transport protocols, dynamics and different solutions are
   needed on the two sides of this border.

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   We now expand the friend-to-friend scenario with a transmorph
   ability, the ability of news to cross the freedom/non-freedom border.

   Alice is a well known blogger in an region with extreme censorship.
   Her identity on Twitter has millions of followers.  However, she has
   no direct ability to reach a Twitter.com server or Internet in
   general.  We assume Alice only has Bob in her friendlist and Bob only
   has Charlie in his friendlist.  Charlie is able to smuggle a
   collection of messages out of the country.  The messages originating
   from Alice should be transmorphed into a series of Twitter post
   belonging to her.

   The identities used in Twitter are highly identifiable labels, with a
   certain trust level.  This hard identity with millions of followers
   is a stark contrasts with anonymity.  Current anti-censorship
   technology lacks the ability to first have stealth encrypted
   transport of news, cross the freedom/non-freedom border and then
   transmorph this news into a public accessible form with a highly
   identifiable label.

4.5.  A single global conversation

   Existing technologies, such as [TOR] in combination with XMPP or the
   Orbot smartphone app facilitate protected point-to-point
   communication.  However, a desired scenario is to facilitate more
   current the Twitter-like social media practices, best typified as a
   "global conversation".

   Furthermore, current social media revolves around video-rich, real-
   time interaction with groups, hashtag-based discovery and social
   networking.  All of these aspects are not offered or are incompatible
   with current-generation of privacy enhancing technology.  More
   knowledge is needed about reputation models in news reporting and
   information flows.  In the current microblogging age, does the number
   of real-person followers be seen as your reputation?  Do several news
   sources of moderate reputation which report the same news story yield
   together an increased reputation score?

   This work should combine privacy enhancement with microblogging.

4.6.  Spammers and hoaxes

   This final scenario is focused on spam.  All technology addressing
   one of the above scenarios MUST also have the capability to deal with
   spam.  Unfortunately, this ability to deal with spam is in conflict
   with simplicity.

   Alice and Bob are exchanging the fresh messages from their social

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   network (similar to Internet-free or Friends-only).  Eve is actively
   trying to disrupt the system by injecting news channels with a mix of
   genuine news, obviously fake messages (consuming valuable system
   resources and user attention) and hoaxes.  These falsehoods made to
   masquerade as truth result in erosion of overall trust in the system.

   Systems SHOULD offer capabilities to report spam, mechanisms for fact
   validation and reputations of (pseudo) identities.

5.  Design principles: simplicity and prior success

   Designing and crafting software which is completely self-organizing
   has clear limits [CAPLIMIT] and requires a certain level of expertise
   [LEVELS].  In order to avoid repeating mistakes from the past, this
   document aims to base itA's design principles on existing new media
   successes.  For microblogging this means following market leading
   solutions and enhance them with censorship resilience.  We recognize
   the following success factors: Simplicity, Real-time responsiveness,
   Near-effortless news creation, News items are bundled in channels,
   combine public broadcasting and person-to-person private messaging,
   following a channel is single direction, more followers yields more
   visibility, keyword search with push of updates and ability to deal
   with spam.

6.  Background rant: lack of coordination and fragmentation

   Computers communicating on equal footing has been part of the IETF
   standards for many decades.  Recently several loosely connected
   standard initiated around explicitly driven by the P2P paradigm for
   applications such as Internet telephony video streaming.  An
   essential problem in this domain is the lack of coordination and
   standard setting for P2P technology.  A large part of the innovation
   around P2P seems to happen in single-person Open Source projects and
   small groups which lack the engineering capacity to make generic, re-
   usable and documented components.  Given their running code-driven
   nature, money and time is not available for attending standards-
   setting meetings, writing formal specifications and defining quality
   control testing suites.  Profit-driven organizations should have the
   resources to overcome these resource shortage issues.  However, due
   to the dynamic, disruptive and litigious nature of P2P few examples
   exist of companies which are capable of supporting an IETF standard
   setting activity for several years.

   As presented during IETF 81 area directorate, there is "not a clear
   long-term architecture yet for you to build actual classes of P2P
   applications using IETF technologies".  Forming an overlay is hard
   and scalable privacy-preserving unstructured search solutions are
   only barely out of the scientific research community.

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   From the above we conclude that a key obstacle to the success of this
   proposal is implementation and uptake.  A draft document, active
   community and reference implementation ideally evolve together over
   time.  To overcome this issue a continuous incremental improvement
   approach is advised.  The preferred way is incremental development of
   single a reference implementation, based on free software.

7.  Current running code and related work

   DISCLAIMER: this section needs significant expansion and listing of
   projects with running code and self-organization.

   Several Open Source projects have running code and partially
   implemented the above four scenarios.  We will briefly list them

   [TOR] A free software implementation of second-generation onion
   routing, a system enabling its users to communicate anonymously on
   the Internet.  This flagship project has boosted online anonymity for
   over a decade and the key example for the cat and mouse dynamics.
   The Orbot project provides an Android implementation of Tor. Due to
   the usage of the client server/model, exit node principle plus lack
   of reputations this architecture is not compatible with our

   [DIASPORA] A free personal web server that implements a distributed
   social networking service.  This partially operational system is
   based on the client/server model and not compatible with our ad-hoc

   [BRIAR] Briar is a secure news and discussion system designed to be
   used by journalists, activists and civil society groups in
   authoritarian countries.  Briar differs from existing circumvention
   tools and mesh networks in three significant ways: needs no external
   infrastructure, can operate over any mixture of available media and
   builds on social relationships.  The aims of this project are similar
   to our scenarios, but this project lacks running code and has few
   active developers.

   [BUBBLE] DTN researchers have simulated closely related scenarios.
   Dissemination in the Arab Spring scenario is likely to involve an
   explicit copy between people who trust each other, referred to as
   social-based forwarding in this study.

   [TWIMIGHT] The Twimight project by ETH-Zurich university shows that
   decentralized microblogging already exists.  Researchers developed an
   Android application that uses Twitter servers in normal conditions,
   but switches to a Bluetooth-based disaster mode when Internet

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   connectivity is lost.

   [MUSUBI] The Musubi smartphone app represents another key,
   censorship-free, technology advancement.  Developed by Stanford
   University, it offers instant messaging service and media sharing
   capabilities similar to WhatsApp, Ping, and Blackberry Messenger.
   What makes it unique is that all data and processing resides on the
   smartphones, not in the cloud.  This decentralization removes the
   need for central processing and provides significant decoupling from
   the underlying infrastructure.  Exchange of cryptographic keys is
   integrated in the friending process--Musubi essentially builds a
   decentralized social graph.  Unfortunately, Musubi is also limited--
   all data transfers go through central servers, as it lacks NAT-
   traversal capability.

   [TRIBLER] DISCLAIMER2: this project is coordinated by the author.
   This project has created Open Source firmware for a Samsung Internet-
   connected television which gives it the ability to find, share and
   stream news videos within a fully self-organizing overlay; operated
   only by remote control [REBELLIONTV].  It is also available as
   generic zero-server file sharing software for the PC which has been
   installed by 1.2 million users.  It uses the Dispersy elastic
   database for providing: keyword search, content discovery, content
   voting and spam prevention using crowd sourcing [DISPERSY].  For
   swarm-based streaming and generic message transport it uses the IETF
   protocol developed within the PPSP working group, called Libswift
   [LIBSWIFT].  All this code is created by a single team and
   specifically designed to facilitate evolution into the prior
   described scenarios.  An Libswift demo streaming app is available on
   the Android market.

8.  Open issues

   Deliverables planned and issues which need to be addressed.

   TODO: ADD REF Privacy definition:


   TODO: http://datatracker.ietf.org/doc/search/ P2P

   TODO: http://datatracker.ietf.org/doc/rfc4981/ SEARCH survey

   TODO: https://datatracker.ietf.org/doc/draft-ietf-p2psip-reload/

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8.1.  Use cases and threat model

8.2.  System components, definitions and system architecture

8.3.  Current technology and gap

8.4.  Detailed system design and protocol specification

9.  Security Considerations


10.  IANA Considerations


11.  References

11.1.  Normative References

   [RFC2119]      Bradner, S., "Key words for use in RFCs to Indicate
                  Requirement Levels", BCP 14, RFC 2119, March 1997.

11.2.  Informative References

   [RFC4787]      Audet, F. and C. Jennings, "Network Address
                  Translation (NAT) Behavioral Requirements for Unicast
                  UDP", BCP 127, RFC 4787, January 2007.

   [RFC4838]      Cerf, V., Burleigh, S., Hooke, A., Torgerson, L.,
                  Durst, R., Scott, K., Fall, K., and H. Weiss, "Delay-
                  Tolerant Networking Architecture", RFC 4838,
                  April 2007.

11.3.  URL References

   [YOUTH]        http://www.nytimes.com/2009/01/25/magazine/
                  25bloggers-t.html, "Revolution, Facebook-Style".

   [FORCEDLOGIN]  http://online.wsj.com/article/
                  SB125978649644673331.html, "Iranian Crackdown Goes

   [NKOREA]       http://audiencescapes.org/sites/default/files/
                  20Korea_InterMedia.pdf, "A QUIET OPENING: NORTH

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   [EGYPTSTUDY]   http://conferences.sigcomm.org/imc/2011/docs/p1.pdf,
                  "Analysis of country-wide internet outages caused by

   [OPENMICRO]    http://xmpp.org/extensions/xep-0277.html, "XEP-0277:
                  Microblogging over XMPP".

   [DATING]       http://www.washingtonpost.com/wp-dyn/content/article/
                  2006/08/05/AR2006080500930.html, "Saudi Youth Use
                  Cellphone Savvy To Outwit the Sentries of Romance".

   [TREND]        http://www.google.com/trends/?q=bluetooth+transfer,
                  "Google Trends query".

   [BOOTSTRAP]    http://grothoff.org/christian/dasp2p.pdf,
                  "Bootstrapping Peer-to-Peer Networks".

   [ZEROKNOW]     http://www.cse.ust.hk/~liu/luli/PT_Trans_final.pdf,
                  "Pseudo trust: Zero-knowledge based authentication in
                  anonymous peer-to-peer protocols".

   [CAPLIMIT]     http://doi.ieeecomputersociety.org/10.1109/MC.2012.54,
                  "The CAP Theorem's Growing Impact".

   [LEVELS]       http://blog.incubaid.com/2012/03/28/
                  level-are-you/, "The Game of Distributed Systems
                  Programming. Which Level Are You?".

   [TOR]          http://www.torproject.org, "Tor Project: Anonymity

   [DIASPORA]     http://diasporaproject.org/, "Diaspora is a fun and
                  creative community that puts you in control.".

   [BRIAR]        https://fulpool.org/btp.pdf, "Secure communication
                  over diverse transports".

   [BUBBLE]       http://dx.doi.org/10.1109/TMC.2010.246, "BUBBLE Rap:
                  Social-Based Forwarding in Delay-Tolerant Networks".

   [TWIMIGHT]     http://dl.acm.org/citation.cfm?id=2159576.2159601,
                  "Twitter in disaster mode: smart probing for
                  opportunistic peers".

   [MUSUBI]       http://dl.acm.org/citation.cfm?id=2187866, "Musubi:
                  disintermediated interactive social feeds for mobile

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   [TRIBLER]      http://dl.acm.org/citation.cfm?id=2206767, "Tribler:
                  P2P search, share and stream".

   [REBELLIONTV]  http://www.tribler.org/trac/wiki/SwiftTV, "RebellionTV
                  a.k.a. Libswift on a television project".

   [DISPERSY]     www.frayja.com/pub/
                  dispersypaper2012.pdf:donotdistribute, "Dispersy
                  elastic database".

   [LIBSWIFT]     http://www.libswift.org, "IETF PPSP streaming protocol

Author's Address

   Johan Pouwelse (editor)
   Delft University of Technology
   Mekelweg 4
   The Netherlands

   Phone: +31 15 278 2539
   EMail: J.A.pouwelse@tudelft.nl

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