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.

127 Relaying dirport requests to Tor download site / website

The idea here was to make it easier to fetch and learn about Tor by making it easy for relays to automatically act as proxies to the Tor website. It needs more discussion, and there are some significant details to work out. It's not at all clear whether this is actually a good idea or not. Probably, there are better choices when it comes to distributing software and updates. (11/2013)

131 Help users to verify they are using Tor [NEEDS-REVISION]

This one is not a crazy idea, but I marked it as needs-revision since it doesn't seem to work so well with our current designs. It seems mostly superseded by proposal 211. (11/2013)

132 A Tor Web Service For Verifying Correct Browser Configuration

This proposal was meant to give users a way to see if their browser and privoxy (yes, it was a while ago) are correctly configured by running a local webserver on 127.0.0.1. I'm not sure the status here. Generally, I'm skeptical of designs that run webservers on localhost, since they become a target for cross-site attacks. (11/2013)

133 Incorporate Unreachable ORs into the Tor Network

This proposal had an idea for letting ORs that can only make outgoing connections still relay data usefully in the network. It's something we should keep in mind, and it's a pretty neat idea, but it radically changes the network topology. Anybody who wants to analyze new network topologies should definitely have a look. (5/2011)

140 Provide diffs between consensuses

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 0.2.7. (See ticket #13339) (2/2015)

141 Download server descriptors on demand

The idea of this proposal was for clients to only download the consensus, and later ask nodes for their own server descriptors while building the circuit through them. It would make each circuit more time-consuming to build, but make bootstrapping much cheaper.

Microdescriptors obsolete a lot of this proposal, and present some difficulties in using in a way compatible with it. (6/2012)

143 Improvements of Distributed Storage for Tor Hidden Service Descriptors

Here's a proposal from Karsten about making the hidden service DHT more reliable and secure to use. It could use more discussion and analysis. We should look into it as part of efforts to improve designs for the next generation of hidden services.

One problem with the analysis here, though, is that it assumes a fixed set of servers that doesn't change. One reason that we upload to N servers at each chosen point in the ring is that the hidden service host and the hidden service client may have different views of which servers exist. We need to re-do the analysis with some fraction of recent consensuses.

This is probably superseded by proposal 224; we should close it IMO. (2/2014)

144 Increase the diversity of circuits by detecting nodes belonging the same provider

This is a version of the good idea, "Let's do routing in a way that tries to keep from routing traffic through the same provider too much!" There are complex issues here that the proposal doesn't completely address, but I think it might be a fine idea for somebody to see how much more we know now than we did in 2008, particularly in light of the relevant paper(s) by Matt Edmann and Paul Syverson. (5/2011)

145 Separate "suitable as a guard" from "suitable as a new guard" [NEEDS-RESEARCH]

Currently, the Guard flag means both "You can use this node as a guard if you need to pick a new guard" and "If this node is currently your guard, you can keep using it as a guard." This proposal tries to separate these two concepts, so that clients can stop picking a router once it is full of existing clients using it as a guard, but the clients currently on it won't all drop it.

It's not clear whether this has anonymity issues, and it's not clear whether the imagined performance gains are actually worthwhile.

This is probably superseded by proposal 236, which has a better approach for weighting guard node selection probabilities; we should probably close this ticket. (2/2015)

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)

159 Exit Scanning

This is an overview of SoaT, with some ideas for how to integrate it into Tor. (5/2011)

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)

172 GETINFO controller option for circuit information 173 GETINFO Option Expansion

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)

175 Automatically promoting Tor clients to nodes

Here's Steven's proposal for adding a mode between "client mode" and "relay mode" for "self-test to see if you would be a good relay, and if so become one." It didn't get enough attention when it was posted to the list; more people should review it. (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)

185 Directory caches without DirPort

The old HTTP directory port feature is no longer used by clients and relays under most circumstances. The proposal explains how we can get rid of the requirement that non-bridge directories have an open directory port. (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)

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)

194 Mnemonic .onion URLs

Here's one of several competing "let's make .onion URLs human-usable" proposals. This one makes sentences using a fixed map. This kind of approach is likely to obsoleted if we go ahead with current plans for hidden services that would make .onion addresses much longer, though. (11/2013)

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)

196 Extended ORPort and TransportControlPort

Here are some remaining pieces of the pluggable transport protocol that give Tor finer control over the behavior of its transports. Much of this is implemented in 0.2.5 now; we should figure out what's left, and whether we want to build that. (11/2013)

197 Message-based Inter-Controller IPC Channel

This proposal is for an architectural enhancement in Tor deployments, where Tor coordinates communications between the various programs (Vidalia, TorBrowser, etc) that are using it. (6/2012)

199 Integration of BridgeFinder and BridgeFinderHelper

Here's a proposal for how Tor can integrate with a client program that finds bridges for it. I've seen some work being done on things called "BridgeFinder"; I don't know what the status of the current proposal is, though. (11/2013)

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. (11/2013)

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)

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)

211 Internal Mapaddress for Tor Configuration Testing

Here, the idea is to serve an XML document over HTTP that would let the know when it's using Tor. The XML document would be returned when you make a request over Tor for a magic address in 127.0.0.0/8. I think we need to do _something_to solve this problem, but I'm not thrilled with the idea of having any more magical addresses like this; we got rid of .noconnect for a reason, after all. (11/2013)

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)

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)

220 Migrate server identity keys to Ed25519 v This one is a design to migrate server identity keys to Ed25519 for improved security margin. It needs more analysis of long-term migration to other signing key types -- what do we do if we want to add support for EdDSA over Curve3617 or something? Can we make it easier than this? And it also needs analysis to make sure it enables us to eventually drop RSA1024 keys entirely.

I've started building this in #12498, though, so we'd better figure out out fairly soon. Other proposals, like 224, depend on this one. (2/2015)

223 Ace: Improved circuit-creation key exchange

Here's an interesting one. It proposes a replacement for the ntor handshake, using the multi-exponentiation optimization, to run a bit faster at an equivalent security level.

Assuming that more cryptographers like the security proof, and that the ntor handshake winds up being critical-path in profiles as more clients upgrade to 0.2.4 or 0.2.5, this is something we should consider. (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)

225 Strawman proposal: commit-and-reveal shared rng

Proposal 224's solutions for bug #8244 require that authorities regularly agree upon a shared random value which none of them could have influenced or predicted in advance. This proposal outlines a simple one that isn't perfect (it's vulnerable to DOS and to limited influence by one or more collaborating hostile authorities), but it's quite simple, and it's meant to start discussion.

I hope that we never build this, but instead replace it with something better. Some alternatives have already been discussed on tor-dev; more work is needed, though. (12/2013)

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)

228 Cross-certifying identity keys with onion keys

This proposal signs each server's identity key with its onion keys, to prove onion key ownership in the router descriptor. It's not clear that this actually improves security, but it fixes an annoying gap in our key authentication. I have it coded up in my #12498 branch, targetting 0.2.7. (2/2015)

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)

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)

238 Better hidden service stats from Tor relays [DRAFT]

Here's an important one that needs many eyes. George Kadianakis, David Goulet, Karsten Loesing, and Aaron Johnson wrote this to describe a mechanism for the tor network to securely produce aggregate hidden service usage statistics without exposing sensitive intermediate results. This has an implementation in 0.2.6 and should probably be marked closed. (2/2015)

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)

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)

241 Resisting guard-turnover attacks [DRAFT]

I wrote this one with good ideas from Aaron Johnson and Rob Jansen. It describes a way to respond to an important class of attacks where an adversary kills off a targeted user's guards until the user has chosen a guard the attacker controls. (See the "Sniper Attack") paper. The defense is tricky, and if not done right, might lead clients to kick themselves off the network out of paranoia. So, this proposal could use more analysis. (2/2015)

Since last time:

Proposal 140 and 227 have been implemented and closed.

Proposal 215 was implemented and closed

Proposals 230 through 241 are new.