August 2012 - tor-dev - lists.torproject.org

Another key exchange algorithm for extending circuits: alternative to ntor?
by Nick Mathewson 11 Aug '12

11 Aug '12

Hi, all! Michael Backes, Aniket Kate, and Esfandiar Mohammadi have a paper in submission called, "An Efficient Key-Exchange for Onion Routing". It's meant to be more CPU-efficient than the proposed "ntor" handshake. With permission from Esfandiar, I'm sending a link to the paper here for discussion. http://www.infsec.cs.uni-saarland.de/~mohammadi/owake.html What do people think? -- Nick

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[Stegotorus] Strange comparison in chop_circuit_t::send_targeted(conn, blocksize)
by vmon 10 Aug '12

10 Aug '12

Hey Zack, Please take a look at this comparison in chop_circuit_t::send_targeted(conn, blocksize): if (avail > blocksize - lo) avail = blocksize - lo; else if (avail > SECTION_LEN) avail = SECTION_LEN; else if (upstream_eof && !sent_fin) // this block will carry the last byte of real data to be sent in // this direction; mark it as such op = op_FIN; Assume SECTION_LEN = 65536 suppose avail = 67000 blocksize - lo = 66500 => avail = 66500 avail = 67000 blocksize - lo = 67500 => avail = 65536 it's like that if avail is very big then the it is OK if it's bigger than SECTION_LEN but if it's moderately big then it shouldn't be bigger than SECTION_LEN, which seems very arbitrary. On the other hand if blocksize - lo < SECTION_LEN again it doesn't make sense, because then it never reaches to (avail > SECTION_LEN). So it's like if SECTION_LEN < blocksize - lo the behavior is random and if it's SECTION_LEN > blocksize - lo is useless. Moreover, when blocksize - lo > avail > SECTION_LEN I'm getting assertion error in the other overload of send_targeted. Everything makes sense and the assertion failure goes away if I replace the code with this: if ((avail > blocksize - lo) || (avail > SECTION_LEN)) { avail = min(blocksize - lo, SECTION_LEN); } else if (upstream_eof && !sent_fin) // this block will carry the last byte of real data to be sent in // this direction; mark it as such op = op_FIN; Please tell me what you think and if the second chunk is the correct replacement? Bests, vmon

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Re: [tor-dev] Another key exchange algorithm for extending circuits: alternative to ntor?
by aniket kate 09 Aug '12

09 Aug '12

> Date: Thu, 9 Aug 2012 00:22:59 +0000 > From: Robert Ransom <rransom.8774(a)gmail.com> > > On 8/8/12, Nick Mathewson <nickm(a)freehaven.net> wrote: > >> Michael Backes, Aniket Kate, and Esfandiar Mohammadi have a paper in >> submission called, "An Efficient Key-Exchange for Onion Routing". >> It's meant to be more CPU-efficient than the proposed "ntor" >> handshake. With permission from Esfandiar, I'm sending a link to the >> paper here for discussion. >> >> http://www.infsec.cs.uni-saarland.de/~mohammadi/owake.html >> >> What do people think? > > > * If you finish my implementation of the Ed25519 group operations > (which you would need in order to implement this protocol), you can > use them to implement a signature-based protocol (specified as > A-DHKE-1 in http://eprint.iacr.org/1999/012) which requires only one > precomputed and one on-line exponentiation per protocol run on the > server when implemented with a slightly modified version of Ed25519. > (The client's performance is much less important than the server's.) I went through A-DHKE-1 description (Page 36 of Eprint 1999/012). I find that A-DHKE-1 also requires one online signature generation on the server side along with one online exponentiation. Therefore, A-DHKE-1 is computationally more expensive than the discussed protocol and probably even the ntor protocol based on the employed signature scheme. -Aniket

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How about virtual machines?
by Admin 09 Aug '12

09 Aug '12

Hello Developers, My testing shows that you can setup encrypted virtual machines in a country with easy access to broadband, and have someone from a country where good computer hardware is hard to find, the Internet got cut off to a point where only dial up is available, and manage to give these people access to broadband and high range hardware. In order to do this, you need to setup a remote desktop virtualization, where the user is able to use all of the resources of a virtual machine, while only using it's current device for rendering the screen of the vm and as keyboard, mouse or touch input. This virtual machine could reset it's state once the user logs off, leaving no trace of what he did while he was on it. Considering the only connection the user is actually making is to the vm location, there is way an oppressive government can figure out which sites are currently being visited or what the user is doing, unless it is already inside taking screenshots and keylogging. There is also the possibility of making cheap dial up enabled USB dongles, which are specialized in screen rendering by PCoIP and can be connected to any device, such as a smart tvs and tablets. Testing shows you can make Android virtual machines for those connecting through a touch enabled device, and keep the device's touch functions. Let me know what you think. Cheers

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Is it possible to run private Exit nodes?
by SiNA Rabbani 08 Aug '12

08 Aug '12

I have been running private bridges for my VIP contacts for a long time. I use PublishServerDescriptor 0 to keep my bridges private. Is it possible to also run a private Exit node? What would happen, if I hard coded an exit into my torrc that is not published (if possible at all)? All the best, SiNA -- “If I had eight hours to chop down a tree, I’d spend the first six of them sharpening my axe.” -Abraham Lincoln

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Next Tor release timeframes?
by Roger Dingledine 08 Aug '12

08 Aug '12

1) Do we have any requirements to release an 0.2.4.1-alpha at any particular date? I haven't been following e.g. the latest SponsorG timelines. 2) Nick was enthusiastic about an 0.2.2.38 with the latest fix. Nick, do you still think that's important? My sense is that it's a totally esoteric theoretical attack where there's no rush to release. 3) For the next 0.2.3 rc, we might want to merge at least: https://trac.torproject.org/projects/tor/ticket/6252 https://trac.torproject.org/projects/tor/ticket/6404 --Roger

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[patch] fix vidalia compilation in gcc 4.7
by Jason A. Donenfeld 08 Aug '12

08 Aug '12

Fixed in a gentoo bug report: https://422645.bugs.gentoo.org/attachment.cgi?id=320722

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http_apache_steg_t is working now
by vmonmoonshine＠gmail.com 08 Aug '12

08 Aug '12

Hey Zack, I have pushed the working version of http_apache_steg_t. On server side it asks apache for the load, on the client side it uses the url dictionary and parameter values. http_apache_steg_t is inherited from http_steg_t. But because of all those macro hackish tricks (which expect you to inherit only from steg_t), it feels bit odd (when c++ natively support polymorphism maybe we don't need these macros). So you can test it writing http_apache instead of http in the command line. (but you need apache installed on server side and you need to run payload_scraper first) Downstream client to server is only curl now and hence probably more robust while passing proxies. It's blocking though. I'll make non-blocking in near future. I'm going to implement the protocol for passing the dictionary from the server to client in following few days and spends next week testing, writing tests and applying your comments on github (including spelling and grammatical mistakes :p ) Cheers, vmon P.S. I'm slowly re-styling stuff in the steg directory to c++ style, meanwhile it might look even uglier and messier, but it'll be pretier at end.

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Re: [tor-dev] #6512 [Stem]: TorExport Module and Unit Testing
by Erik I Islo 07 Aug '12

07 Aug '12

Hi Damian, Looking at coverage the test provides, I was under the impression that the various cases of include_fields and exclude fields (e.g. if they overlap) should also be tested, but if you find that unnecessary, that would help explain why my unit tests were difficult to follow. In the mocking changes that I made, I added functionality for mocking functions that take keyword arguments. Though it is no longer necessary with the new unit tests, I was wondering if there was something I could have done better with that code as it seems such functionality may come in useful in the future. You may have already noticed this (and your documentation is consistent with this), but just to be sure, the new export code won't work with generators, which I bring up as this is what server_descriptor.parse_file() returns. So a user of this module would need to covert that generator into a list or tuple, which could be rather large. >>> def gener(list=[1,2,3,4]): ... for item in list: ... yield item >>> gener()[0] Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: 'generator' object has no attribute '__getitem__' Working with Professor Danner this summer (and from the CS classes I have taken so far), I am under the impression that run-time type checking can be expensive and generally falls outside of the realm of 'pythonic' code. To help Megan and I understand this design change, could you explain why you went with this style (e.g. line 83 in stem/descriptor/export.py)? Along similar lines, why wouldn't we also check the types of other parameters passed into the function? Thank you in advance for answering these questions -- this summer has been (and still is) a phenomenal learning experience for us, and gaining insight on coding style and the like is crucial to developing our own coding techniques. Looking at the code, I must apologize. I didn't mean to take so much of your time rewriting the code. That said, looking at your implementation gave me some perspective in evaluating the code I submitted so I don't make similar mistakes in the future. Best, Erik On Sat, Aug 4, 2012 at 3:22 PM, Tor Bug Tracker & Wiki < torproject-admin(a)torproject.org> wrote: > #6512: TorExport Module and Unit Testing > > ----------------------------+----------------------------------------------- > Reporter: ErikI | Owner: atagar > Type: enhancement | Status: closed > Priority: normal | Milestone: > Component: Stem | Version: > Resolution: implemented | Keywords: > Parent: | Points: > Actualpoints: | > > ----------------------------+----------------------------------------------- > Changes (by atagar): > > * status: needs_review => closed > * resolution: => implemented > > > Comment: > > Thanks Erik, merged with some revisions [1]. I found the unit tests a bit > hard to follow, especially since it wasn't broken down by the test cases > so I rewrote those. Let me know if I missed any test cases that you think > are important. > > [1] > > https://gitweb.torproject.org/stem.git/commitdiff/7022021c4207a0066cb932616… > > -- > Ticket URL: < > https://trac.torproject.org/projects/tor/ticket/6512#comment:3> > Tor Bug Tracker & Wiki <https://trac.torproject.org/> > The Tor Project: anonymity online >

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[GSoC] Stem descriptor parsing - Status update
by Ravi Chandra Padmala 07 Aug '12

07 Aug '12

Hello I spent the last two weeks implementing the network status document parser and the microdescriptor consensus parser. The network status document parsing code is ready for review here[1]. It's a fairly large amount of code, with ~1.4K new LoC. The microdescriptor consensus parser is much simpler, since it reuses most of the network status document parsing code. I'll be uploading that soon. I should be working on the controller's event handling methods after that. 1. https://trac.torproject.org/projects/tor/ticket/6569 -- neena

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