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Improving Private Browsing Mode/Tor Browser
by Georg Koppen 29 Jul '11

29 Jul '11

After reading Mike's blog post and the material contained in it (via links) I thought it would be helpful to start a discussion about it. First of all thanks for explaining the idea of improving the private browsing mode. That aim seems worthwile but I want to focus more on the needs for high anonymity systems like Tor (I am one of the JonDos people to set the records straight). Thus, first I am not sure about the relationship of the improved private browsing and the anon mode. It seems like the former is kind of precondition of the latter and the latter adds some special anon features (or just layout stuff??): "We would love to be able to ship a vastly simplified browser extension that contains only a compiled Tor binary and some minimal addon code that simply "upgrades" the user's private browsing mode into a fully functional anonymous mode." What shall the upgrade do exactly? And why having again add-ons that can probably be toggled on/off and are thus more error-prone than just having an, say, Tor anon mode? Or is this already included in the Tor anon mode but only separated in the blog post for explanatory purposes? Sticking to the blog post (one of) its central idea seems to be to isolate the identifiers and state to the top-level domain in the URL bar as "activity in Tor Browser on one site should not trivially de-anonymize their activity [i.e. the activity of Tor users, G.K.] on another site to ad networks and exits". I am wondering whether this idea really helps here at least regarding exit mixes. If one user requests google.com, mail.google.com and other Google services within the 10 minutes interval (I am simplifying here a bit) without deploying TLS the exit is still able to connect the whole activity and "sees" which services that particular user is requesting/using. Even worse, if the browser session is quite long there is a chance of recognizing that user again if she happens to have the same exit mix more than once. Thus, I do not see how that helps avoiding linkability for users that need/want strong anonymity while surfing the web. Would be good to get that explained in some detail. Or maybe I am missing a point here. Now something to the proposed behavior of the referer and window.name. It is said that they should adhere to the "same-origin policy where sites from different origins get either no referer, or a referer that is truncated to the top-level domain". Assuming I understood TorButton's Smart-Spoofing option properly: Why is it not applied to the referer/window.name anymore? In other words: Why is the referer (and window.name) not kept if the user surfs within one domain (let's say from example.com to foo.example.com and then to foo.bar.example.com)? Before we implemented almost the same algorithm than Torbutton's smart-spoof algo in our own extension a while ago we had some compatibility issues (I remember yahoo.com that needed to have the referer untouched while surfing within the domain) that got fixed by it and never popped up again. Why stepping back? The idea "sites should also be allowed to request an exemption to this rule on a per-site basis using an html attribute, which could trigger a chrome permissions request, or simply be granted automatically (on the assumption that they could just URL smuggle the data)" seems rather awkward and not a good solution to a problem that is not really one. One final point: Leaving my previous section aside: Why is the referer and window.name not treated in the same way as cookies and others in the proposal. Why having two different policies for identifiers? I am not sure whether there could emerge some attacks out of that distinction but my feeling tells me that there should ideally be just one policy that governs all those identifiers. At least it would probably be easier to implement and to audit them. Georg

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Report from the "Tor ecosystem" BoF at DebConf 11
by Jérémy Bobbio 29 Jul '11

29 Jul '11

Hi! Here is a report from DebConf 11, the annual conference of the Debian project. We had the opportunity to hold a "Tor ecosystem" BoF. It was short (we had only 45 minutes), but productive from my perspective. Here's an (obviously partial) report. A lot more people showed up (± 25) than we expected for a pure work meeting, so there is definitely an interest in having Tor and its ecosystem working well in Debian. Among the attendees we had: * Peter Palfrader, maintainer of the 'tor' package, * Ulises Vitulli, (co-)maintainer of 'vidalia', 'tor-arm', 'python-torctl', 'torchat', * Jérémy Bobbio, maintainer of 'torbutton', * intrigeri and bertagaz, developers of Tails (which is a live system based on Debian). A summary follows from some notes and memory. Feel free to correct me if you feel that things happened differently. New upstream packaging policy ============================= We took some time to discuss the changes to the packaging policy that were proposed by Andrew Lewman last June. See <https://lists.torproject.org/pipermail/tor-dev/2011-June/002780.html> Quoting the relevant part: GNU/Linux (deb and rpm) 1. tor-client. The same TBB we ship today. 2. tor-relay. Create tor-relay.(deb|rpm) that includes geoipdb and a pre-configured torrc that is for a non-exit relay. 3. tor-exit-relay. Create tor-exit-relay.(deb|rpm) that includes geoipdb and a pre-configured torrc that is for an exit relay. 4. tor-bridge. Create tor-bridge.(deb|rpm) that includes geoipdb and a pre-configured torrc that is for a bridge. The 'tor' source package in Debian already builds a binary package called 'tor-geoipdb' which contains GeoIP information. We have not even discussed about changing, as it is how it is supposed to be in Debian (pure data package as separate, architecture-independent packages). The proposed 'tor-client' and TBB in general was discussed later. For the rest, the hard part of the discussion also revolved around defining who are target users of these packages. Pure desktop users? People that can fiddle with a command-line and edit a configuration file? Experienced sysadmins? Having 3 different "configuration" packages for relays, exit-relays and bridges is something that could be done in Debian. But we had a rough consensus that it would actually complicate things for most Debian users. For bridges, pure desktop users would probably benefit from a better integration with Vidalia; so that made us rule out the need for a dedicated 'tor-bridge' package. Which left us with the "relay" and "exit relay" use cases and it looked like those could be better adressed by either a debconf question, or by some examples better integrated. Integration with other software, derivatives and custom distributions ===================================================================== While discussing how we could actually make it easier to setup relays, we got back to the lack of a way to source extra configuration files in `torrc`. We outlined some benefits that would have a `/etc/tor/torrc.d` directory full of configuration snippets: * The 'tor' package will not (or less) need patches to change the default settings. * It would make it much easier to implement example setups (relays, exit relays, bridges) either through a debconf question or through a system script like 'tor-setup-relay'. * Tails developers will only need to drop a very small extra configuration file instead of having to rewrite the whole, which should ease development and reviewing. * Other packages which need a hidden service to work (e.g. 'onioncat') would be able to create it automatically by installing the proper configuration snippet. That would enable them to work right after being installed. Feature request: https://trac.torproject.org/projects/tor/ticket/2863 Control of the system-wide 'tor' daemon ======================================= We finally have (currently in 'experimental') an easy way for applications to control the system-wide 'tor' daemon: the ControlSocket option is on by default. Vidalia, ARM and others now only require users to be in the system 'debian-tor' group to be able to control Tor. We did not have the time to properly discuss if, and how, we offer an easy way to add users to this group. Tor Browser Bundle (e.g tor-client) =================================== There is an incentive to have something as close as the Tor Browser Bundle in Debian. Otherwise, desktop users on Debian get a smaller anonymity set (such strong partitioning already happened in the past, see <http://bugs.debian.org/595375>). The main issue is the Tor fork of Firefox. There are a few possibilities on how it can be handled within Debian. Summary: this is doable, but requires a lot of work, and the cooperation of quite a few different parties. One other thing that TBB is doing is to start its own instance of Tor. We agreed that it was a behaviour that would be quite desirable to have. It will make setup even more easier and it might limit users exposure when they are not using Tor. In order to achieve that, we need either to make the 'tor' package not start Tor after being installed or we need a way have the `tor` binary without the rest of the daemon infrastructure (e.g initscript). The former will probably be quite confusing to sysadmins, so we agreed on splitting out the daemon binary from the current 'tor' package to a new 'tor-bin' package. How TorBrowser could get in Debian? =================================== Having a full separate source package for TorBrowser is not possible due to Debian Policy 4.13. But there are still other options, all having their shortcomings: 1. Make the 'iceweasel' source package (that's how Firefox is called in Debian due to trademark issues) produce an extra 'tor-browser' binary package. Issues: - Mike Hommey (iceweasel maintainer) stated clearly that he did not want to maintain the Tor patches. But we can probably settle on a policy like "if it does not build, just drop it". The removal of a binary package does not trigger NEW queue processing. It is also not triggered if the same binary packages returns before two weeks. - Double (?) the build time of 'iceweasel' which is already huge. Security team will not be happy, and it's going to be harder to actually maintain the TorBrowser side of things. Pros: until the patches do not apply anymore, it'll be less maintainance from our side. 2. Make the 'iceweasel' source package produce an extra binary package (e.g 'iceweasel-src') that will contain the full Iceweasel source. Create a 'tor-browser' package that Build-Depends on the former. Issues: - 'iceweasel' is a pretty fast moving target. This will need us to follow its uploads quite closely to ask for binNMU or to upload updated versions quickly. - The security team will have two packages to track instead of one. They might not like it at all. Pros: much easier for Mike Hommey and we are autonomous to upload the 'tor-browser' package if changes are only needed there. Looks like the latter is probably better. But it definitely needs to be checked with all parties involved first. For browser extensions curretly shipped with TBB, Debian already has 'torbutton' and 'noscript'. But we miss 'httpseverwhere' (#591579) and 'betterprivacy'. There are a few open issues that still need to be figured out: * TorBrowser should create dedicated profiles in the user home directories, * How can default values be set? Do we need 'locked down' preferences? * How should we handle other system-wide extensions? Active like for the main Iceweasel, totally ignored, or disabled by default? * If Debian ships the TorBrowser, should we prevent Torbutton from appearing in the usual Iceweasel? This will require a lot of work for the initial bootstrap and a decent amount of work for the daily maintainance after that. But it looked worthwhile anyhow… Cheers, -- Jérémy Bobbio .''`. lunar(a)debian.org : :Ⓐ : # apt-get install anarchism `. `'` `-

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New mailing list for wiki changes
by Karsten Loesing 25 Jul '11

25 Jul '11

Hi everyone, yesterday we found that a few people run their own rss-to-email service to be notified of wiki changes. We decided that it's easier to set up a new mailing list that has all the wiki changes and that everyone can subscribe to. If you're interested in learning when something in the wiki changed, subscribe to: https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-wiki-changes (And if you have suggestions to make the r2e output more useful, please say so. The current configuration is simply 'r2e add "https://trac.torproject.org/projects/tor/timeline?wiki=on&max=50&daysback=2…" tor-wiki-changes(a)lists.torproject.org'.) Best, Karsten

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New Paper: Cloud-based Onion Routing
by Nick Jones 15 Jul '11

15 Jul '11

Hi All, I'm a graduate student at Princeton, and our research group has recently submitted a paper proposing a design for cloud based onion routing. The goal of our research is to securely perform onion routing on cloud based infrastructure (like Amazon EC2 and Rackspace) while allowing users to retain the same (or almost the same) privacy as when using Tor. We distribute trust across multiple cloud providers, and use Chaum's e-cash for payment and access control. Additionally, we hope that the elasticity of cloud infrastructure will make cloud based OR more censorship resistant than current systems. This project is still in a relatively early stage, and we would love to get feedback from the Tor community. We would welcome any comments/questions/criticisms. Our project's website is available at: http://sns.cs.princeton.edu/projects/cor/ A direct link to our paper is here: http://www.cs.princeton.edu/~najones/publications/cor-foci11.pdf Our abstract: Internet censorship and surveillance have made anonymity tools increasingly critical for free and open Internet access. Tor, and its associated ecosystem of vol- unteer traffic relays, provides one of the most secure and widely-available means for achieving Internet anonymity today. Unfortunately, Tor has limitations, including poor performance, inadequate capacity, and a susceptibility to wholesale blocking. Rather than utilizing a large number of volunteers (as Tor does), we propose mov- ing onion-routing services to the “cloud” to leverage the large capacities, robust connectivity, and economies of scale inherent to commercial datacenters. This paper de- scribes Cloud-based Onion Routing (COR), which builds onion-routed tunnels over multiple anonymity service providers and through multiple cloud hosting providers, dividing trust while forcing censors to incur large collat- eral damage. We discuss the new security policies and mechanisms needed for such a provider-based ecosys- tem, and present some preliminary benchmarks. At to- day’s prices, a user could gain fast, anonymous network access through COR for only pennies per day. Thanks! Nick Jones

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Re: [tor-dev] CPU utilization for relay
by swsnyder＠snydernet.net 15 Jul '11

15 Jul '11

Mike Perry wrote: >Thus spake swsnyder at snydernet.net (swsnyder at snydernet.net) > >> FYI, this is a profile of my Tor v0.2.2.30-rc relay, taken in a 10-minute sampling: >> >> CPU: CPU with timer interrupt, speed 0 MHz (estimated) >> Profiling through timer interrupt >> samples % linenr info symbol name >> 3126 29.7290 cast-586.s:9 CAST_encrypt > >Can you attach gdb to your relay and set a breakpoint for >CAST_encrypt? We have no idea why this function should be called at >all (unless it is for something like reading keyfiles off disk?) let >alone dominate your profile output. I didn't break on CAST_encrypt() either in a running process or in tor started from a gdb command line. Either way, I could set a breakpoint on the symbol but never actually got there. I think the symbols were screwed-up from building Tor with GCC's Profile Guided Optimization. When I built the same code without PGO I get this from another 10-minute run: CPU: CPU with timer interrupt, speed 0 MHz (estimated) Profiling through timer interrupt samples % linenr info symbol name 2386 58.6241 x86-mont.s:8 bn_mul_mont 262 6.4373 aes-586.s:269 _sse_AES_encrypt_compact 207 5.0860 sha1-586.s:8 sha1_block_data_order 199 4.8894 aes-586.s:424 _x86_AES_encrypt 189 4.6437 aes-586.s:1610 _x86_AES_decrypt 55 1.3514 aes.c:329 aes_crypt_inplace 48 1.1794 di_ops.c:97 tor_memeq Breakpoints *do* hit on bn_mul_mont(). I assume the reduced number of samples is a result of only having half as many active connection as the prior profiling run. Thanks for the reply.

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Re: [tor-dev] [tor-relays] CPU utilization for relay
by Mike Perry 15 Jul '11

15 Jul '11

Thus spake swsnyder(a)snydernet.net (swsnyder(a)snydernet.net) > FYI, this is a profile of my Tor v0.2.2.30-rc relay, taken in a 10-minute sampling: > > CPU: CPU with timer interrupt, speed 0 MHz (estimated) > Profiling through timer interrupt > samples % linenr info symbol name > 3126 29.7290 cast-586.s:9 CAST_encrypt Can you attach gdb to your relay and set a breakpoint for CAST_encrypt? We have no idea why this function should be called at all (unless it is for something like reading keyfiles off disk?) let alone dominate your profile output. gdb -p <tor_pid> (gdb) break CAST_encrypt (gdb) cont You may need to stick a 'file /usr/bin/tor' or similar in there. If you get no hits, try to do it on startup: gdb /usr/bin/tor (gdb) break CAST_encrypt Function "CAST_encrypt" not defined. Make breakpoint pending on future shared library load? (y or [n]) y (gdb) run [<tor args>] If you get any hits, run 'backtrace' and give us the output. You may need to install some debuginfo packages, but gdb should tell you this if so. If anyone playing along at home gets any hits on either of these breakpoints, let us know. > 1677 15.9486 sha256-586.s:8 sha256_block_data_order > 1149 10.9272 aes-586.s:424 _x86_AES_encrypt > 844 8.0266 sha1-586.s:8 sha1_block_data_order > 273 2.5963 crypto.c:1649 crypto_digest_get_digest > 221 2.1018 md32_common.h:283 SHA1_Update > 182 1.7309 encode.c:190 EVP_EncodeBlock > 171 1.6262 OpenBSD_malloc_Linux.c:1793 ifree > 136 1.2934 cast-586.s:379 CAST_decrypt > 130 1.2363 md32_common.h:348 SHA1_Final > 127 1.2078 obj_lib.c:66 OBJ_dup > 122 1.1602 memarea.c:221 memarea_alloc > 110 1.0461 aes-586.s:1610 _x86_AES_decrypt > > After running for 14 hours, the Tor relay has consumed 1.6% of CPU time. It is now using 45MB of RAM, servicing 112 active connections. > > According to http://torstatus.blutmagie.de my Max/Burst/Observed (Bps) bandwidth is: > > 153600 / 307200 / 127170 > > Environment: > > CPU: Pentium-M (Dothan) @ 1.80 GHz > RAM: 1.0 GB DDR1 > Net: Fast Ethernet connected to a Surfboard cable modem > > CentOS v5.6 > Tor v0.2.2.30-rc > libevent 2.0.12-stable > openssl 1.0.0d > zlib 1.2.5 > glibc 2.5-58 > > Just another data point. > > > _______________________________________________ > tor-relays mailing list > tor-relays(a)lists.torproject.org > https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-relays -- Mike Perry Mad Computer Scientist fscked.org evil labs

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Nick's planned schedule for Tor 0.2.3.x development
by Nick Mathewson 14 Jul '11

14 Jul '11

Hi, all! I'll try to avoid a long-winded mail and instead cut to the chase: I want Tor releases to come out more frequently, and I'm going to plan a release schedule for 0.2.3 to make sure it happens. It's July 2011 now; I want to get 0.2.3.x released in early 2012. To that end, I'm going to declare the following tentative and somewhat arbitrary schedule: December 1, 2011: Big feature freeze. No new features that "feel big" to me get merged into 0.2.3.x after this date, barring exceptional circumstances[*]. January 6, 2012: Feature freeze. Barring exceptional circumstances, no new features get merged to 0.2.3.x after this date, barring exceptional circumstances[*]. Fixes for non-regression bugs (that is, those that also existed in 0.2.2.x) may also get deferred if they aren't too severe. Some time between Jan 6 and Jan 30: we fork off a maint-0.2.3 branch and have master become 0.2.4. When it's ready, 2012: We release 0.2.3.x-rc, see how long everything took us, and adjust our plans or 0.2.4.x. Note that the deadlines above are _merge_ freezes, not _submission_ freezes. If you give me a big patch on Dec 1, and it needs more review or revision than can get done that day, then it needs to wait for 0.2.4. Obviously, this is still up for discussion. But please remember about the bikeshed. Also, please keep the following in mind: * Delaying a release in order to merge "one more feature" means that every *other* feature in the release gets delayed so that the "one more feature" can hit stable earlier. * If we can actually get releases out on a 7-9 month schedule (or better), the impact of making a feature wait for the next release becomes less severe than it's been in the past. [*] Let's not waste time trying in advance to enumerate exceptional circumstances. yrs, -- Nick

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Using routers as bridges
by Rob van der Hoeven 14 Jul '11

14 Jul '11

Hi folks, Bridges serve as "unknown" entry points to the TOR network. For this, part of the TOR network nodes are reserved and unlisted. This is not good for the performance of the network, and because the network is relatively small i think the unlisted-nodes strategy will only be a short term solution. At the moment i'm working on my own FreedomBox. From this work i got the following idea: Why not use the DNAT function of a router to forward TOR traffic to a TOR node? This way you don't need unlisted nodes anymore. A router-bridge does not have to be a full TOR node.... Unfortunately the standard DNAT functionality of most routers only support DNAT from the internet to internal addresses. So you need modified firmware to make this work. Maybe a (slightly modified?) version of OpenWRT will work. Router-bridges have a second advantage over real TOR nodes. They can be easily moved. If a router-bridge gets blocked, you can simply give the router-bridge to a friend. To give you an example of internet-internet DNAT i have configured one of my systems to forward traffic to the TOR website. The URL is: https://wordpress.hoevenstein.nl/ (If you try the URL you get a message about an invalid certificate of course) Let me know what you think about this idea... Rob van der Hoeven. http://freedomboxblog.nl

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Tor Relay Setup Wizard
by Damian Johnson 14 Jul '11

14 Jul '11

Hi all. Over the last few weeks I've been working on a relay setup wizard for arm. Its purpose is to make volunteering to be a relay easy, narrowing the options to those most commonly used and giving nice descriptions/defaults to encourage good configurations. At present relay setup for new users, particularly exits, is either confusing or limited. For users doing it without a controller we have a deluge of man page options and a confusing bundle of docs. For Vidalia users, however, it's easy to become a middle hop or bridge, but the configurations it makes for exits are poor (default exit policy, no front page, no notice for how to reduce abuse complaints which probably leads Vidalia exits to be short lived...). This wizard consists of three pages... 1. Selection for what you'd like to be http://www.atagar.com/transfer/tmp/arm_wizard1.png 2. Picking your relay options, with both descriptions of the options and why you'd want to set them http://www.atagar.com/transfer/tmp/arm_wizard2.png 3. Confirmation for the configuration it's making http://www.atagar.com/transfer/tmp/arm_wizard3.png 4. ... then in the frozen land of Nador they were forced to eat Sir Robin's minstrels. And there was much rejoicing. http://www.atagar.com/transfer/tmp/arm_wizard4.png My not-so-humble goals for this wizard is for it to become a method we suggest on the site for setting up an exit (and maybe relays/bridges too later) so I'd appreciate some feedback! The 1.4.3 release candidate is available at... http://www.atagar.com/transfer/tmp/arm-1.4.3rc.tar.bz2 Future plans are automatic signup for Tor Weather and a "Run Tor at Startup" option (this later one is gonna be tricky, but it's vital if we want systems like laptops that frequently shut down to be meaningful relays/bridges). Cheers! -Damian

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(no subject)
by Georg Koppen 11 Jul '11

11 Jul '11

This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --===============7169121415546917615== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig3F72C2734FABE1CB4A827A42" This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig3F72C2734FABE1CB4A827A42 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: quoted-printable >> Hmmm... If that is the answer to my questions then there is nothing like >> avoiding getting tracked by exit mixes in the concept offered in the >> blog post. Okay. >=20 > That is not entirely true. Because identifiers would be linked to > top-level urlbar domain, gone are the days where exits could insert an > iframe or web-bug into any arbitrary page and use that to track the > user for the duration of the session, regardless of page view. >=20 > Instead, they would be pushed back to doing some sort of top-level > redirect (which we hope would be way more visible), or maybe not even > that, depending on how we define redirects with respect to > "top-level". >=20 > So no, we are not completely abandoning exits as an adversary with > this threat model. If I'm wrong about something, or you think there > are still attacks exits can perform that we should address somehow, > let me know. See my last mail. >> Another question came to my mind: You seem to be at pains not to break >> parts of the web even in the anon mode even if that boils down to not >> implement features that would better fit the needs for people looking >> for unlinkability (one thing that comes to my mind here would be having >> a context being tab dependent additionally). Why? Why not saying: "This >> is Tor's anon mode. It is meant for people that strive for unlinkability >> and might break some functionality. You may still use Tor in normal or >> private browsing mode though (providing no or less unlinkability on the >> browser level)." Do you think that's not worth the effort as Tor's IP >> unlinkability is enough here (especially combined with the things you >> suggested in the blog post)? I do not know Tor's user base very well but >> could imagine that it contains a lot of users that would like to have >> more unlinkability than the "we do not want to break any (or almost any) >> part of the web for a better anonymity" fraction. >=20 > I wish I had better science to give you here on the trade-off we're > going for, but the reality is that we're best-guessing over a very > complex cost/benefit landscape. That's true. > We do know for a fact that the easier Tor is to use (which includes > installation, configuration, overall intuitiveness/"familiarity", > compatibility, and performance), the more people will use it > regularly. That seems to hold for every piece of software, I guess. > We also know for a fact that the more people use Tor, the better the > baseline privacy, anonymity, and censorship resistance properties all > become. Agreed. > Hence, I tend to make decisions in favor of the usability direction > over minor details, especially ones that don't really prevent bad > actors/adversaries from accomplishing their goals. That is definitely a good approach. But maybe there is research to be done here as well. Just a rough (and in part research) idea that I had in mind while asking you the question above: What about if we first started looking at different services offered in the web whether they can be deployed anonymously *at all* (or maybe more precisely (but not much): that can be deployed in a way that there is either no linkability at all or the linkability is not strong enough to endanger the user) (that would be worth some research, I guess)? We would probably find some services where we had to say: "Well, there is no way to get them used anonymously due to their nature and the power of the companies and/or owners behind them." (Facebook comes here to my mind as a candidate and the Google universe as well due to the power Google has). Should we say we make the Tor anon mode compatible with these services nevertheless (due to usability issues) and abandon stronger anonymity measures? I would say no. Not at all. Rather we should be honest and say: "Dear User, surfing anonymously AND using Facebook does not work. You may use the Tor anon mode for that purpose though but there is a high probability that it breaks functionality." The idea of getting more users due to being not too strict here might be appealing but is not the right decision in the end. I think one has to realize that there are services in the web that are *designed* in a way that one EITHER may use them OR use anonymity services. Sure, the devil is in the details (e.g. there are probably a lot of services that may be usable anonymously but then are accompanied with a certain lack of usability. What about them? Should we decide against usability again or should we loosen our means to provide unlinkability here?) but that does not mean there is no way to find a good solution though. In short (and still roughly): I would like to start thinking from having all means available to surf the web anonymously and then downgrade them piece-by-piece to reach a trade-off between anonymity and usability. Services that may not be used anonymously at all would not trigger such a painful downgrade ("painful" as one usually tries first to hack around existing problems encountering unbelievable design issues and bugs and has to concede finally that it is in the user's interest to exclude that feature (again)). > The need for science especially comes in on the fingerprinting arena. > Some fingerprinting opportunities may not actually be appealing to > adversaries. Some may even appear appealing in theory, but in practice > would be noticeable to the user, too noisy, and/or too error-prone. > Hence I called for more panopticlick-style studies, especially of > Javascript features, in the blog post. Yes, that is definitely a good idea though I tend to avoid them all even if currently no adversary is using them (especially if no usability issue is at stake). First: no one knows whether one did not miss an attacker using this kind of attack vector and second: Getting rid of attack vectors is a good thing per se. Georg --------------enig3F72C2734FABE1CB4A827A42 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) iQEcBAEBAgAGBQJOGbUuAAoJEKw9P8jZNrM42sIIAKWwpLB+6Aeu97FMeLwJkI/7 blZ98yMsU8fUchIjrkxeTllUX5gcSuI0PSODaMd0lZFEvkFlMAuudcbnC0GmnEVV DP8KV5j8A/RZnVgbEh18AB/keNojnMo/PneCg0109Say2WWqOvL+tklxA14NvgrJ EQlr/P9tmSkdLtwjq5QBQPOVuGNigPk4em2wuSOo1i+7l65VLpfWLYnNwaBEOoGA /ZOKe4h3KLaXiJhaFpvw4d1BoCGAQC2lHb5724qmiTzdFDRAyigewFPxMy8wjO3H mKdPt/WcKw7NfU6jEY7mYRk1D0v3lttjtx9zLwJxwyYXV0rK/DhNiIlJG0uxX8k= =Y0SW -----END PGP SIGNATURE----- --------------enig3F72C2734FABE1CB4A827A42-- --===============7169121415546917615== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ tor-dev mailing list tor-dev(a)lists.torproject.org https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-dev --===============7169121415546917615==--

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