r9345@Kushana: nickm | 2006-10-23 00:52:42 -0400

oops. add latex too


svn:r8798

doc/design-paper/roadmap-2007.tex

@@ -0,0 +1,325 @@
+\documentclass{article}
+
+\newenvironment{tightlist}{\begin{list}{$\bullet$}{
+  \setlength{\itemsep}{0mm}
+    \setlength{\parsep}{0mm}
+    %  \setlength{\labelsep}{0mm}
+    %  \setlength{\labelwidth}{0mm}
+    %  \setlength{\topsep}{0mm}
+    }}{\end{list}}
+\newcommand{\tmp}[1]{{\bf #1} [......] \\}
+
+\begin{document}
+
+\title{Tor Development Roadmap: Wishlist for Nov 2006--Dec 2007}
+\author{Roger Dingledine \and Nick Mathewson \and Shava Nerad}
+
+\maketitle
+\pagestyle{plain}
+
+\section{Introduction}
+Hi, Roger!  Hi, Shava.  This paragraph should get deleted soon.  Right now,
+this document goes into about as much detail as I'd like to go into for a
+technical audience, since that's the audience I know best.  It doesn't have
+time estimates everywhere.  It isn't well prioritized, and it doesn't
+distinguish well between things that need lots of research and things that
+don't.  The breakdowns don't all make sense.  There are lots of things where
+I don't make it clear how they fit into larger goals, and lots of larger
+goals that don't break down into little things. It isn't all stuff we can do
+for sure, and it isn't even all stuff we can do for sure in 2007.  The
+tmp\{\} macro indicates stuff I haven't said enough about.  That said, here
+goes...
+
+Tor (the software) and Tor (the overall software/network/support/document
+suite) are now experiencing all the crises of success.  Over the next year,
+we're probably going to grow more in terms of users, developers, and funding
+than before.  This gives us the opportunity to perform long-neglected
+maintenance tasks.
+
+\section{Code and design infrastructure}
+
+\subsection{Protocol revision}
+To maintain backward compatibility, we've postponed major protocol
+changes and redesigns for a long time.  Because of this, there are a number
+of sensible revisions we've been putting off until we could deploy several of
+them at once.  To do each of these, we first need to discuss design
+alternatives with cryptographers and other outside collaborators to
+make sure that our choices are secure.
+
+First of all, our protocol needs better {\bf versioning support} so that we
+can make backward-incompatible changes to our core protocol.  There are
+difficult anonymity issues here, since many naive designs would make it easy
+to tell clients apart based on their supported versions.
+
+With protocol versioning support would come the ability to {\bf future-proof
+  our ciphersuites}.  For example, not only our OR protocol, but also our
+directory protocol, is pretty firmly tied to the SHA-1 hash function, which
+though not insecure for our purposes, has begun to show its age.  We should
+remove assumptions thoughout our design based on the assumption that public
+keys, secret keys, or digests will remain any particular size infinitely.
+
+A new protocol could support {\bf multiple cell sizes}.  Right now, all data
+passes through the Tor network divided into 512-byte cells.  This is
+efficient for high-bandwidth protocols, but inefficient for protocols
+like SSH or AIM that send information in small chunks.  Of course, we need to
+investigate the extent to which multiple sizes could make it easier for an
+adversary to fingerprint a traffic pattern.
+
+Our OR {\bf authentication protocol}, though provably
+secure\cite{goldberg-tap}, relies more on particular aspects of RSA and our
+implementation thereof than we had initially believed.  To future-proof
+against changes, we should replace it with a less delicate approach.
+
+\subsection{Scalability}
+
+\subsubsection{Improved directory performance}
+Right now, clients download a statement of the {\bf network status} made by
+each directory authority.  We could reduce network bandwidth significantly by
+having the authorities jointly sign a statement reflecting their vote on the
+current network status.  This would save clients up to 160K per hour, and
+make their view of the network more uniform.  Of course, we'd need to make
+sure the voting process was secure and resilient to failures in the network.
+
+We should {\bf shorten router descriptors}, since the current format includes
+a great deal of information that's only of interest to the directory
+authorities, and not of interest to clients.  We can do this by having each
+router upload a short-form and a long-form signed descriptor, and having
+clients download only the short form.  Even a naive version of this would
+save about 40\% of the bandwidth currently spent on descriptors.
+
+We should {\bf have routers upload their descriptors even less often}, so
+that clients do not need to download replacements every 18 hours whether any
+information has changed or not.  (As of Tor 0.1.2.3-alpha, clients tolerate
+routers that don't upload often, but routers still upload at least every 18
+hours to support older clients.)
+
+\subsubsection{Non-clique topology}
+Our current network design achieves a certain amount of its anonymity by
+making clients act like each other through the simple expedient of making
+sure that all clients know all servers, and that any server can talk to any
+other server.  But as the number of servers increases to serve an
+ever-greater number of clients, these assumptions become impractical.
+
+At worst, if these scalability issues become troubling before a solution is
+found, we can design and build a solution to {\bf split the network into
+multiple slices} until a better solution comes along.  This is not ideal,
+since rather than looking like all other users from a point of view of path
+selection, users would ``only'' look like 200,000--300,000 other users.
+
+We are in the process of designing {\bf improved schemes for network
+  scalability}.  Some approaches focus on limiting what an adversary can know
+about what a user knows; others focus on reducing the extent to which an
+adversary can exploit this knowledge.  These are currently in their infancy,
+and will probably not be needed in 2007, but they must be designed in 2007 if
+they are to be deployed in 2008.
+
+\subsubsection{Relay incentives}
+
+\tmp{We need incentives to relay.}
+
+\subsection{Portability}
+Our {\bf Windows implementation}, though much improved, continues to lag
+behind Unix and Mac OS X, especially when running as a server.  We hope to
+merge promising patches from Mike Chiussi to address this point, and bring
+Windows performance on par with other platforms.
+
+We should have {\bf better support for portable devices}, including modes of
+operation that require less RAM, and that write to disk less frequently (to
+avoid wearing out flash RAM).
+
+\subsection{Performance: resource usage}
+
+\tmp{Use less RAM when we have little.  Make buffer code smarter}
+
+\tmp{Allow separate bandwidth buckets for different bandwidth classes}  This
+gets us more users happy to run servers.
+
+\tmp{Write-limiting for directory servers}
+
+\tmp{Don't use so many sockets} We can save some for hidden services and for
+  encrypted directories.
+
+\subsection{Performance: network usage}
+
+\tmp{Do research to figure out how well capacity is actually used.}
+
+\tmp{Tune pathgen algorithms to use it better.}
+
+
+\subsection{Blue-sky: UDP}
+
+\section{Blocking resistance}
+
+\subsection{Design for blocking resistance}
+We have written a design document explaining our general approach to blocking
+resistance.  We should workshop it with other experts in the field to get
+their ideas about how we can improve Tor's efficacy as an anti-censorship
+tool.
+
+
+\subsection{Implementation: client-side and bridges-side}
+Our anticensorship design calls for some nodes to act as ``bridges'' that can
+circumvent a national firewall, and others inside the firewall to act as pure
+clients.  The design here is quite clear-cut; we're probably ready to begin
+implementing it.  To implement bridges, we need only to have servers publish
+themselves as limited-availability relays to a special bridge authority if
+they judge they'd make good servers.  Clients need a flexible interface to
+learn about bridges and to act on knowledge of bridges.
+
+Clients also need to {\bf use the encrypted directory variant} added in Tor
+0.1.2.3-alpha.  This will let them retrieve directory information over Tor
+once they've got their initial bridges.
+
+Bridges will want to be able to {\bf listen on multiple addresses and ports}
+if they can, to give the adversary more ports to block.
+
+Additionally, we should {\bf resist content-based filters}.  Though an
+adversary can't see what users are saying, some aspects of our protocol are
+easy to fingerprint {\em as} Tor.  We should correct this where possible.
+
+\subsection{Implementation: bridge authorities}
+Our design anticipates an arms race between discovery methods and censors.
+We need to begin the infrastructure on our side quickly, preferably in a
+flexible language like Python, so we can adapt quickly to censorship.
+
+\section{Security}
+
+\subsection{Security research projects}
+
+\tmp{Mixed-latency}
+
+\tmp{long-distance padding}
+
+\tmp{router-zones}
+
+\tmp{defenses against end-to-end correlation}  We don't expect any to work
+right now, but it would be useful to learn that one did.  Alternatively,
+proving that one didn't would free up researchers in the field to go work on
+other things.
+
+\subsection{Implementation security}
+
+\tmp{Encrypt more keys}
+
+\tmp{Talk Coverity or somebody with a copy of vs2005 into running tools on
+  our code}
+
+\tmp{Directory guards}
+
+\subsection{Detect corrupt exits and other servers}
+
+\tmp{Improved feedback mechanism for tools like SOAT to use}
+
+\tmp{More tools like SOAT: check for routers that bork SSL, routers that
+  sniff (and use) passwords...}
+
+\tmp{Add a way for authorities to declare families.}
+
+\tmp{Make authority administration simpler so authority ops spend less time
+  on random junk and more time on care and feeding of the network.}
+
+\tmp{Authorities should measure Stable (and maybe Fast) themselves, and not
+  just believe declared router uptime.}
+
+\subsection{Protocol security}
+
+\tmp{Build in hooks for DoS-resistance: when we need it, we'll really need
+  it.}
+
+
+\section{Development infrastructure}
+
+\subsection{Build farm}
+We've begun to deploy a cross-platform distributed build farm of hosts
+that build and test the Tor source every time it changes in our development
+repository.
+
+We need to {\bf get more participants}, so that we can test a larger variety
+of platforms.  (Previously, we've only found out when our code had broken on
+obscure platforms when somebody got around to building it.)
+
+We need also to {\bf add our dependencies} to the build farm, so that we can
+ensure that libraries we need (especially libevent) do not stop working on
+any important platform between one release and the next.
+
+\subsection{Improved testing harness}
+Currently, our {\bf unit tests} cover only about XX\% of the code base.  This
+is uncomfortably low; we should write more and switch to a more flexible
+testing framework.
+
+We should also write flexible {\bf automated single-host deployment tests} so
+we can more easily verify that the current codebase works with the network.
+
+\subsection{Centralized build system}
+We currently rely on a separate packager to maintain the packaging system and
+to build Tor on each platform for which we distribute binaries.  Separate
+package maintainers is sensible, but separate package builders has meant
+long turnaround times between source releases and package releases.  We
+should create the necessary infrastructure for us to produce binaries for all
+major packages within an hour or so of source release.
+
+\subsection{Improved metrics}
+\tmp{We'd like to know how the network is doing.}
+
+\tmp{We'd like to know where users are in an even less intrusive way.}
+
+\tmp{We'd like to know how much of the network is getting used.}
+
+\subsection{Controller library}
+\tmp{release a general-purpose controller library}
+
+\section{User experience}
+
+\subsection{Get blocked less, get blocked less hard}
+\tmp{Implement  and publicize blind-signature based credential scheme}
+
+\tmp{Maybe make a minimal RBL thing}
+
+\subsection{All-in-one bundle}
+\tmp{a.k.a ``Torpedo'', but rename this.}
+
+\subsection{LiveCD Tor}
+\tmp{a.k.a anonym.os done right}
+
+\subsection{Interface improvements}
+\tmp{Allow controllers to manipulate server status.}
+
+\subsection{Firewall-level deployment}
+\tmp{Make our new TransPort logic more portable and tested}
+
+\tmp{Write logic for Tor to act as a DNS server}
+
+\tmp{Write necessary glue code, scripts, and docs so users who want to use
+  Tor as a firewall-like thing can.  Consider a livecd.}
+
+\subsection{Localization}
+Right now, most of our user-facing code is internationalized.  We need to
+internationalize the last few hold-outs (like the Tor installer), and get
+more translations for the parts that are already internationalized.
+
+Also, we should look into a {\bf unified translator's solution}.  Currently,
+since different tools have been internationalized using the
+framework-appropriate method, different tools require translators to localize
+them via different interfaces.  Inasmuch as possible, we should make
+translators only need to use a single tool to translate the whole Tor suite.
+
+\section{Documentation}
+
+\subsection{Unified documentation scheme}
+
+\tmp{Keep track of all the docs we've got}
+
+\tmp{Unify the docs into a single book-like thing}  This will also help us
+identify what sections of the ``book'' are missing.
+
+\subsection{Missing technical documentation}
+
+\tmp{Revised design paper, or design paper plus errata}
+
+\tmp{``How to play nice with Tor''}
+
+
+
+
+
+\end{document}