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[Last updated 9 Sep 2015]

This is an update to the Tor proposal status overview.  I last sent one
of these out almost a year ago; since 0.2.6 has entered feature freeze,
I really ought to do this regularly again.

Future versions of this document will be maintained in the torspec
repository as "proposals/proposal-status.txt".  I'll still send them
to tor-dev periodically.

If you're looking for something to review, think about, or comment
on:

     Review 219 if you're a DNS geek, or you'd like Tor to work
     better with more DNS types.

     Review 220 (ed25519 identity keys) and 228
     (cross-certification) if you like designing signature things,
     if you have good ideas about future-proofing key type
     migration, or if you care about making Tor servers' identity
     keys stronger.

     Review 223 (ACE handshake) if you're a cryptographer, or a
     cryptography implementer, and you'd like an even faster
     replacement for the ntor handshake.

     Review 224 if you want to look through a big, complex protocol
     with a lot of pieces. Also review it if you care about hidden
     services and making them better.

     Review 226 if you're interested in bridgedb development.

     Review 241 for a big chance at making Tor clients and hidden services
     more secure.

     Review something else if you want to take a possibly good idea
     that needs more momentum and promote it, fix it up, or finally
     kill it off.

I note in passing that many of the proposals below seem stalled,
perhaps permanently: some because we don't know how to answer their
open questions, others because we're not sure if they're a good
idea, others because they don't seem implementable yet.  Is that the
best way to characterize it?  Should we have a new "stalled"
proposal status or something?  Should we have a
"rejected-pending-revision" status that we use effectively for
everything that doesn't seem likely to get revised or implemented
any time soon?  Other suggestions would be welcome.

Finally: if you've sent something to tor-dev or to me that should
have a proposal number, but doesn't have one yet, please ping me
again to remind me!

**NOTE**: The dates after each paragraph indicate when I last
          revised the paragraph.


140  Provide diffs between consensuses [ACCEPTED]

     This proposal describes a way to transmit less directory
     traffic by sending only differences between consensuses, rather
     than the consensuses themselves.  Daniel Marti implemented this for his
     GSoC project last summer; it is still under revision and on target
     for merge into 0.2.8.  (See ticket #13339)  (9/2015)

156  Tracking blocked ports on the client side

     This proposal provides a way for clients to learn which ports
     they are (and aren't) able to connect to, and connect to the
     ones that work.  It comes with a patch, too.  It also lets
     routers track ports that _they_ can't connect to.

     I'm a little unconvinced that this will help a great deal: most
     clients that have some ports blocked will need bridges, not
     just restriction to a smaller set of ports.  This could be good
     behind restrictive firewalls, though.

     The router-side part is a little iffy: routers that can't
     connect to each other violate one of our network topology
     assumptions, and even if we do want to track failed
     router->router connections, the routers need to be sure that
     they aren't fooled into trying to connect repeatedly to a
     series of nonexistent addresses in an attempt to make them
     believe that (say) they can't reach port 443.

     This one is a paradigmatic "open" proposal: it needs more
     discussion.  The patch probably also needs to be ported to
     0.2.3.x; it touches some code that has changed.

     This is likely also to be relevant for the ideas of proposal 241,
     and maybe superseded by some version of that proposal. (2/2015)

164  Reporting the status of server votes

     This proposal explains a way for authorities to provide a
     slightly more verbose document that relay operators can use to
     diagnose reasons that their router was or was not listed in the
     consensus.  These documents would be like slightly more verbose
     versions of the authorities' votes, and would explain *why* the
     authority voted as it did.  It wouldn't be too hard to
     implement, and would be a fine project for somebody who wants
     to get to know the directory code. (5/2011)

165  Easy migration for voting authority sets

     This is a design for how to change the set of authorities without
     having a flag day where the authority operators all reconfigure
     their authorities at once.  It needs more discussion.  One
     difficulty here is that we aren't talking much about changing the
     set of authorities, but that may be a chicken-and-egg issue, since
     changing the set is so onerous.

     If anybody is interested, it would be great to move the discussion
     ahead here. (5/2011)

168  Reduce default circuit window

     This proposal reduces the default window for circuit sendme
     cells.  I think it's implemented (or mostly implemented) in
     0.2.1.20?  If so, we should make sure that tor-spec.txt is
     updated and close it. (11/2013)

     Should update Tor-spec, should close this. (9/2015)

     Actually, wait, did we ever implement this?  Ugh. (9/2015)

172  GETINFO controller option for circuit information [accepted]
173  GETINFO Option Expansion [accepted]

     These would help controllers (particularly arm) provide more
     useful information about a running Tor process.  They're
     accepted and some parts of 173 are even implemented: somebody
     just needs to implement the rest. (5/2011)

177  Abstaining from votes on individual flags

     Here's my proposal for letting authorities have opinions about some
     (flag,router) combinations without voting on whether _every_ router
     should have that flag.  It's simple, and I think it's basically
     right.  With more discussion and review, somebody could/should
     build it, I think. (11/2013)

182  Credit Bucket

     This proposal suggests an alternative approach to our current
     token-bucket based rate-limiting, that promises better
     performance, less buffering insanity, and a possible end to
     double-gating issues. (6/2012)

188  Bridge Guards and other anti-enumeration defenses

     This proposal suggests some ways to make it harder for a relay
     on the Tor network to enumerate a list of Tor bridges. Worth
     investigating and possibly implementing. (6/2012)
189  AUTHORIZE and AUTHORIZED cells
190  Bridge Client Authorization Based on a Shared Secret [NEEDS-REVISION]
191  Bridge Detection Resistance against MITM-capable Adversaries

     Proposal 187 reserved the AUTHORIZE cell type; these
     proposals suggests how it could work to try to make it
     harder to probe for Tor bridges. They need more alternatives
     and attention, and possibly some revision and analysis.
     Number 190 needs revision, since its protocol isn't actually
     so great. (11/2013)

     Mark as RESERVE? (9/2015)

192  Automatically retrieve and store information about bridges

     This proposal gives an enhancement to the bridge information
     protocol, where clients remember more things about bridges, and
     are able to update what they know about them over time.  Could
     help a lot with bridge churn. (6/2012)

     Mark as RESERVE? Do we still even want this? (9/2015)

195  TLS certificate normalization for Tor 0.2.4.x

     Here's the followup to proposal 179, containing all the parts
     of proposal 179 that didn't get built, and a couple of other
     tricks besides to try to make Tor's default protocol less
     detectable.  I'm pretty psyched about the part where we let
     relays drop in any any self-signed or CA-issued certificate
     that they like.  Some of this is done in ticket #7145;
     we should decide, however, how much we want to push towards
     normalizing the main Tor protocol. Some of the NSA documents
     published in Der Spiegel this past December imply that this kind of
     fingerprinting can be helpful for snoops; we should take another
     look at it. (2/2015)

     I think we should take a pass over this, pick the parts we still
     think are relevant, and call them ACCEPTED. (9/2015)

--- 
201  Make bridges report statistics on daily v3 network status requests

     Here's a proposal for bridges to better estimate the number of
     bridge users. (6/2012)

202  Two improved relay encryption protocols for Tor cells

     Here's a sketch of the two broad classes of alternatives for
     improving how relay encryption works. Right now, progress on this
     proposal is stalled waiting for the ideal wide-block construction
     to come along the line.  AEZ seems like it might be close to what
     we need. Other cryptographers are also looking at designs that
     might be a good match. (9/2015)

203  Avoiding censorship by impersonating an HTTPS server

     This one is a design for making a bridge that acts like an
     HTTPS server (by *being* an HTTPS server) until the user
     proves they know it's a bridge. (11/2013)

     Didn't we do something like this? (9/2015)

209  Tuning the Parameters for the Path Bias Defense

     In this proposal, Mike discusses alternative parameters for
     getting better result out of the path-bias-attack detection
     code. (11/2013)

210  Faster Headless Consensus Bootstrapping

     This proposal suggests that we get our initial consensus by
     launching multiple connections in parallel, and fetching the
     consensus from whichever one completes. In my opinion, that
     would be a fine idea when we're fetching our initial
     consensus from non-Authority DirSources, but we shouldnt' do
     anything to increase the load on authorities.  (11/2013)

     This needs an update; it's a pretty good idea, and Mike and Roger
     like it.  It goes will with FallbackDirSource stuff. (9/2015)

212  Increase Acceptable Consensus Age

     This proposal suggests that we increase the maximum age of a
     consensus that clients are willing to use when they can't
     find a new one, in order to make the network robust for
     longer against a failure to reach consensus.  In my
     opinion, we should do that.  If I recall correctly, there
     was some tor-dev discussion on this one that should get
     incorporated into a final, implementable version. (11/2013)

     Mark as ACCEPTED? Needs another review first! (9/2015)

219  Support for full DNS and DNSSEC resolution in Tor

     Here's a design to allow Tor to support a full range of DNS
     request types. It probably isn't adequate on its to make
     DNSSEC work realistically, since naive DNSSEC requires many
     round trips that wouldn't be practical over Tor.  It has a
     ton of inline discussion that needs to get resolved before
     this is buildable.

     One thing to consider here is whether we can get the server-side
     done with reasonable confidence, and figure out the client side
     once more servers have upgraded.  (12/2013)

224  Next-Generation Hidden Services in Tor

     This proposal outlines a more or less completely revised version
     of the Tor hidden services protocol, improved to accomodate
     better cryptography, better scalability, and defenses for
     several attacks we'd never considered when we did the original
     design.

     Some parts of this one are clearly right; some (like
     scalability) are entirely unwritten. This proposal needs a lot
     of attention and improvements to get it done right. I hope to
     implement this over the course of 2015-2016. (2/2015)

226  Scalability and Stability Improvements to BridgeDB:
     Switching to a Distributed Database System and RDBMS

     This one outlines design and behavior changes for a seriously
     refactored bridgedb.  (2/2014)

     I should find out if Isis has a status update for this. (9/2015)

229  Further SOCKS5 extensions

     Here's a nice idea for how we can support a new SOCKS5 protocol
     extension to relay information between clients and Tor, and
     between Tor and pluggable transports, more effectively.  It
     also adds some additional SOCKS5 error codes. There are some
     open questions to answer. "Trunnel" has an implementation of
     the protocol extension formats in its examples directory. (2/2015)

230  How to change RSA1024 relay identity keys [DRAFT]
231  Migrating authority RSA1024 identity keys [DRAFT]

     Who remembers the OpenSSL "Heartbleed" vulnerability?
     These proposals I wrote try to explain safer mechanisms for a bunch
     of servers to migrate their RSA1024 identity keys at once.  I'm not
     sure we'll be able to build thee, though: implementating proposal
     220 above seems cleverer to me. (2/2015)

     Proposal 220 is in progress, and will retroactively SUPERSEDE this
     one. (9/2015)

232  Pluggable Transport through SOCKS proxy [OPEN]

     Arturo Filastò wrote this proposal for chaining pluggable
     transports which themselves need to go through proxies. Seems
     potentially useful! (2/2015)

233  Making Tor2Web mode faster [OPEN]

     This one by Virgil, Fabio, and Giovanni describes a couple of ways
     that Tor2Web builds of Tor can save some circuit hops that they use
     today.  Potentially useful for Tor2Web; any implementation needs to
     be sure that it never changes the behavior of non-tor2web clients.
     (2/2015)

234  Adding remittance field to directory specification [OPEN]

     Virgil, Leif, and Rob added this proposal for relays to specify
     payment addresses for schemes that want to compensate relay
     operators for their use of bandwidth.  (2/2015)

235  Stop assigning (and eventually supporting) the Named flag [DRAFT]

     This proposal is about removing the Named flag.  (Thanks to
     Sebastian Hahn for writing it!)  The rationale is that the naming
     system for relays never worked particularly well, and it had
     strange and hard-to-explain security properties.  We've implemented
     the key part of this already: directory authorities don't assign
     the Named flag any longer.  Next up will be removing client support
     for parsing and understanding it. (2/2015)

236  The move to a single guard node [OPEN]

     This proposal suggests that to limit client fingerprinting, and to
     limit opportunities for attacks, clients should use a single guard
     node, rotated infrequently.  This transition is in progress; we use
     a single guard node for circuit traffic now, but in order to make
     guards more long-lived, we need to adjust how they are chosen.
     George has a patch for that as #9321, targetting inclusion into
     0.2.6.  (Thanks to George Kadianakis and Nicholas Hopper for
     writing this one.) (2/2015)

237  All relays are directory servers [OPEN]

     Matthew Finkel wrote this proposal to describe a transition to a
     world where Tor relays can be directory servers without having an
     open DirPort -- and eventually, where every relay can be a
     DirServer.  He has an implementation, possibly for 0.2.6 or 0.2.7,
     in ticket #12538.  (2/2015)

     Compare to proposal 185; it may supersede that one.  Review again
     and mark as accepted maybe?  (9/2015)

239  Consensus Hash Chaining [DRAFT]

     Here's the start of a good idea that Andrea Shepard wrote up (with
     some help from Nick).  The idea is to make it hard even for a set
     of corrupt authorities (or authority-key-thieves) to make a
     personalized false consensus for a target user, by authenticating
     the whole sequence as a hash chain.  Others on tor-dev suggested
     improvements and had good questions (thanks, Leif and Sebastian G!)
     (2/2015)

     Needs revisions while we still remember what those revisions are.
     (9/2015)

240  Early signing key revocation for directory authorities [DRAFT]

     This one is another Andrea+Nick collaboration about certificate
     revocation for our most sensitive keys.  If an authority key needs
     to be replaced, it would be great to take the old one out of
     circulation as fast as possible.  Peter Palfrader on tor-dev had
     some ideas for making this better. (2/2015)

     Needs revisions while we still remember what those revisions are.
     (9/2015)

242  Better performance and usability for the MyFamily option [OPEN]

     Describes a mechanism for using a new ed25519 signature type to
     reduce the complexity of adding nodes to a family and the size of
     family lines. (9/2015)

245  Deprecating and removing the TAP circuit extension protocol [DRAFT]

     Explains a migration path for finally removing all support for the
     TAP circuit extension protocol over several Tor versions. (9/2015)

246  Merging Hidden Service Directories and Introduction Points [OPEN]

     XXXX

247  Defending Against Guard Discovery Attacks using Vanguards [DRAFT]

     XXXX

248  Remove all RSA identity keys [DRAFT]

     Explains a migration path for removing RSA1024 identity keys in the
     future, once all Tor instances support Ed25519 identity
     keys. (9/2015)

249  Allow CREATE cells with >505 bytes of handshake data [DRAFT]

     Explains how to split CREATE cells (and other stuff) across
     multiple RELAY_EXTEND cells.  This one will be helpful if we want
     to add support for some kind of circuit extension protocol
     containing a postquantum forward-secure handshake, like ntru or
     ring-lwe. (9/2015)

250  Random Number Generation During Tor Voting [DRAFT]

     Describes a commit-and-reveal protocol for creating shared
     randomness among the authorities during the voting process. Required
     for a few other proposals, such as 224. (9/2015)

251  Padding for netflow record resolution reduction [DRAFT]

     Proposes a periodic "keepalive-like" packet be sent over quiet Tor
     connections, so that incidental netflow record collection in
     default router configurations reveals less about when flows begin
     and end.

252  Single Onion Services [DRAFT]

     XXXX

253  Out of Band Circuit HMACs [DRAFT]

     Allows participating nodes to authenticate the whole contents of a
     circuit point-to-point so as to better resist or detect some kinds
     of tagging attacks. (9/2015)

254  Padding Negotiation [DRAFT]

     Describes general mechanisms and new cells/commands for requesting
     various types of padding between clients and relays, for use in defending
     against both website traffic fingerprinting as well as hidden service
     circuit setup fingerprinting. (9/2015)

255  Controller features to allow for load-balancing hidden services [DRAFT]

     Specifies a technique to improve the scalability of hidden services by
     decoupling the introduction and rendezvous functionality so that they can
     be performed in separate physical machines.

256  Key revocation for relays and authorities [OPEN]

     Specifies how directory authorities and relays can revoke compromised
     long-term identity keys.

257  Refactoring authorities and making them more isolated from the net [META]

     Describes a strategy for making directory authorities less vulnerable to
     DoS by reducing their exposure to the network.

258  Denial-of-service resistance for directory authorities [ACCEPTED]

     Describes heuristics that directory authorities can deploy to reduce the
     threat of DoS due to large directory connection volumes.

259  New Guard Selection Behaviour [OBSOLETE]

     Specifies an improved guard-picking algorithm that is capable of defending
     against targetted attacks. The proposal has since been obsoleted by
     proposal 271.

260  Rendezvous Single Onion Services [FINISHED]

     Specifies a performance optimization for hidden service that do not care
     about location anonymity, so that they build 1-hop circuits instead of
     3-hop circuits to reduce communication latency.

261  AEZ for relay cryptography [OPEN]

     Specifies a circuit encryption scheme that is resistant to tagging
     end-to-end correlation attacks.

262  Re-keying live circuits with new cryptographic material [OPEN]

     Specifies a way to rekey our circuit crypto so that we allow greater
     amounts of encrypted data through them.

263  Request to change key exchange protocol for handshake v1.2 [OBSOLETE]

     Specifies a quantum-safe key agreement algorithm for Tor circuits. The
     proposal was supereceded by proposal 269.

264  Putting version numbers on the Tor subprotocols [CLOSED]

     Specifies a way for relays to do versioning using their descriptors. In
     the past we used the Tor version string for versioning, which is not an
     elegant approach.

265  Load Balancing with Overhead Parameters [ACCEPTED]

     The proposal provides new load balancing equations for Tor which are
     capable of taking into account non-standard traffic like padding or
     directory and hidden service traffic.

266  Removing current obsolete clients from the Tor network [DRAFT]

     Specifies ways to disable outdated and insecure Tor clients.

267  Tor Consensus Transparency [DRAFT]

     Specifies how to apply the certificate transparency approach of TLS to Tor
     consensus and vote documents, in an attempt to make attacks more easily
     detectable.

268  New Guard Selection Behaviour [DRAFT]

     Specifies an improved guard-picking algorithm that is capable of defending
     against targetted attacks. The proposal has since been obsoleted by
     proposal 271.

269  Transitionally secure hybrid handshakes [DRAFT]

     Describes a generalised protocol for composing X25519 key exchanges with
     post-quantum ones.

270  RebelAlliance: A Post-Quantum Secure Hybrid Handshake Based on NewHope [DRAFT]

     Describes a hybrid handshake based on the ntor handshake and the
     NewHope post-quantum key exchange.  Currently needs revision to
     specify how this proposal depends upon prop#269.

271  Another algorithm for guard selection [OPEN]

     Specifies an improved guard-picking algorithm that is capable of defending
     against targetted attacks.

272  Listed routers should be Valid, Running, and treated as such [FINISHED]

     This proposal describes a change in how clients understand consensus
     flags, and how authorities vote on consensuses.

273  Exit relay pinning for web services [DRAFT]

     The proposal specifies a scheme for websites to prevent additional
     security against malicious exit nodes, by specifying their own set of exit
     nodes.

279  A Name System API for Tor Onion Services [DRAFT]

     The proposal specifies a modular system for integrating naming systems
     (GNS, Namecoin, etc.) with Tor onion services.

294  TLS 1.3 Migration [DRAFT]

     A work-in-progress draft proposal detailing the process of
     migrating to TLS 1.3 (which is not yet finalised at the time of
     this writing) and which parts of our current, more idiosyncratic,
     uses of TLS can be removed.

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