remove some of the done items, in preparation for overhaul

svn:r13085

doc/design-paper/roadmap-future.tex

@@ -14,8 +14,8 @@
 
 \begin{document}
 
-\title{Tor Development Roadmap: Wishlist for Nov 2006--Dec 2007}
-\author{Roger Dingledine \and Nick Mathewson \and Shava Nerad}
+\title{Tor Development Roadmap: Wishlist for 2008 and beyond}
+\author{Roger Dingledine \and Nick Mathewson}
 
 \maketitle
 \pagestyle{plain}
@@ -26,23 +26,13 @@
 
 
 \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
-%plangoes...
 
 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.
+suite) are now experiencing all the crises of success.  Over the next
+years, we're probably going to grow more in terms of users, developers,
+and funding than before. This document attempts to lay out all the
+well-understood next steps that Tor needs to take. We should periodically
+reorganize it to reflect current and intended priorities.
 
 \section{Code and design infrastructure}
 
@@ -96,22 +86,6 @@ significantly.  Sadly, many of these are patented and unavailable for us.
 \subsection{Scalability}
 
 \subsubsection{Improved directory efficiency}
-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.\plan{Must do; specify in 2006. 2 weeks to specify, 3-4 weeks to
-  implement.}
-
-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 by clients downloading
-descriptors.\plan{Must do; specify in 2006. 3-4 weeks.}
 
 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
@@ -154,11 +128,12 @@ have some preliminary designs~\cite{incentives-txt,tor-challenges},
 but need to perform
 some more research to make sure they would be safe and effective.\plan{Write
   a draft paper; 2 person-months.}
+(XXX we did that)
 
 \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
+merge promising patches from Christian King to address this point, and bring
 Windows performance on par with other platforms.\plan{Do in 2007; 1.5 months
   to integrate not counting Mike's work.}
 
@@ -166,10 +141,6 @@ 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).\plan{Optional; 2 weeks.}
 
-We should {\bf stop using socketpair on Windows}; instead, we can use
-in-memory structures to communicate between cpuworkers and the main thread,
-and between connections.\plan{Optional; 1 week.}
-
 \subsection{Performance: resource usage}
 We've been working on {\bf using less RAM}, especially on servers.  This has
 paid off a lot for directory caches in the 0.1.2, which in some cases are
@@ -181,20 +152,8 @@ chunks produced with a specialized allocator.)  This could potentially save
 around 25 to 50\% of the memory currently allocated for network buffers, and
 make Tor a more attractive proposition for restricted-memory environments
 like old computers, mobile devices, and the like.\plan{Do in 2007; 2-3 weeks
-  plus one week measurement.}
-
-We should improve our {\bf bandwidth limiting}.  The current system has been
-crucial in making users willing to run servers: nobody is willing to run a
-server if it might use an unbounded amount of bandwidth, especially if they
-are charged for their usage.  We can make our system better by letting users
-configure bandwidth limits independently for their own traffic and traffic
-relayed for others; and by adding write limits for users running directory
-servers.\plan{Do in 2006; 2-3 weeks.}
-
-On many hosts, sockets are still in short supply, and will be until we can
-migrate our protocol to UDP.  We can {\bf use fewer sockets} by making our
-self-to-self connections happen internally to the code rather than involving
-the operating system's socket implementation.\plan{Optional; 1 week.}
+  plus one week measurement.} (XXX We did this, but we need to do something
+more/else.)
 
 \subsection{Performance: network usage}
 We know too little about how well our current path
@@ -272,39 +231,25 @@ tool.
 
 \subsection{Implementation: client-side and bridges-side}
 
-Our anticensorship design calls for some nodes to act as ``bridges''
-that are outside a national firewall, and others inside the firewall to
-act as pure clients.  This part of the design is quite clear-cut; we're
-probably ready to begin implementing it.  To {\bf implement bridges}, we
-need to have servers publish themselves as limited-availability relays
-to a special bridge authority if they judge they'd make good servers.
-We will also need to help provide documentation for port forwarding,
-and an easy configuration tool for running as a bridge.
-
-To {\bf implement clients}, we need to provide a flexible interface to
-learn about bridges and to act on knowledge of bridges. We also need
-to teach them how to know to use bridges as their first hop, and how to
-fetch directory information from both classes of directory authority.
-
-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. We may want to get the rest of the
-Tor user base to begin using this encrypted directory variant too, to
-provide cover.
-
 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.
 
 \subsection{Research: anonymity implications from becoming a bridge}
 
+see arma's bridge proposal; e.g. should bridge users use a second layer of
+entry guards?
+
 \subsection{Implementation: bridge authority}
 
-The design here is also reasonably clear-cut: we need to run some
+we run some
 directory authorities with a slightly modified protocol that doesn't leak
 the entire list of bridges. Thus users can learn up-to-date information
 for bridges they already know about, but they can't learn about arbitrary
 new bridges.
 
+we need a design for distributing the bridge authority over more than one
+server
+
 \subsection{Normalizing the Tor protocol on the wire}
 Additionally, we should {\bf resist content-based filters}.  Though an
 adversary can't see what users are saying, some aspects of our protocol are
@@ -313,10 +258,6 @@ easy to fingerprint {\em as} Tor.  We should correct this where possible.
 Look like Firefox; or look like nothing?
 Future research: investigate timing similarities with other protocols.
 
-\subsection{Access control for bridges}
-Design/impl: password-protecting bridges, in light of above.
-And/or more general access control.
-
 \subsection{Research: scanning-resistance}
 
 \subsection{Research/Design/Impl: how users discover bridges}
@@ -398,14 +339,6 @@ resist these attacks, or can improve our design to resist them, we should.
   unless a graduate student is interested.}
 
 \subsection{Implementation security}
-Right now, each Tor node stores its keys unencrypted.  We should {\bf encrypt
-  more Tor keys} so that Tor authorities can require a startup password.  We
-should look into adding intermediary medium-term ``signing keys'' between
-identity keys and onion keys, so that a password could be required to replace
-a signing key, but not to start Tor.  This would improve Tor's long-term
-security, especially in its directory authority infrastructure.\plan{Design this
-  as a part of the revised ``v2.1'' directory protocol; implement it in
-  2007. 3-4 weeks.}
 
 We should also {\bf mark RAM that holds key material as non-swappable} so
 that there is no risk of recovering key material from a hard disk
@@ -458,11 +391,11 @@ them as belonging to the same family.\plan{Do during v2.1 directory protocol
 To avoid attacks where an adversary claims good performance in order to
 attract traffic, we should {\bf have authorities measure node performance}
 (including stability and bandwidth) themselves, and not simply believe what
-they're told.  Measuring stability can be done by tracking MTBF.  Measuring
-bandwidth can be tricky, since it's hard to distinguish between a server with
+they're told. We also measure stability by tracking MTBF.  Measuring
+bandwidth will be tricky, since it's hard to distinguish between a server with
 low capacity, and a high-capacity server with most of its capacity in
-use.\plan{Do ``Stable'' in 2007; 2-3 weeks.  ``Fast'' will be harder; do it
-  if we can interest a grad student.}
+use. See also Nikita's NDSS 2008 paper.\plan{Do it if we can interest
+a grad student.}
 
 {\bf Operating a directory authority should be easier.}  We rely on authority
 operators to keep the network running well, but right now their job involves