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Pluggable transports meeting tomorrow (Friday 22nd of November 2013)
by George Kadianakis 21 Nov '13

21 Nov '13

Greetings humans, this is an email to remind you that there the regular biweekly pluggable transports meeting is going to happen tomorrow. Place is the #tor-dev IRC channel in OFTC. Time is 17:00 UTC. Cheers!

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Help me guague how full your plate is via regular check-in conversations
by Tom Lowenthal 20 Nov '13

20 Nov '13

Hello fighters for freedom, When applying for grants, planning future work, and otherwise thinking about what capacity we have leftover to do things in the future, it's really useful to know who's doing what and how much of it. I get some of this information from our sponsor/project-specific meetings, but it doesn't seem to be the full picture, so I'd like to trot out that old chestnut of regular one-on-one chats. This means that I'd like to spend between thirty and sixty minutes talking with each of you, once every week or two. I'd like to calibrate the frequency so that we can get calls down to 30 minutes each, with room to kvetch and have a conversation that's a little more than just rattling off deliverable status and time assignments. I think that the right group for this is the folks who post to tor-reports. If you post to tor-reports, please get back to me by the end of the week with your availability for a regular weekly check-in, as well as any thoughts you have about medium, format, or anything else. If you're not currently on tor-reports and think you should check in, or vice versa, you should probably drop me a line too. Any questions or suggestions? -Tom

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Proposal 223: Ace: Improved circuit-creation key exchange
by Nick Mathewson 20 Nov '13

20 Nov '13

Hi, all! Here's Esfandiar Mohammadi's proposal for the Ace handshake. It should have been added as a numbered proposal back in July; I think I lost track of everything while the dev meeting was happening. Please let me know if you have more proposals that should be assigned numbers but haven't gotten one yet. Filename: 223-ace-handshake.txt Title: Ace: Improved circuit-creation key exchange Author: Esfandiar Mohammadi Created: 22-July-2013 Status: Open History: 22-July-2013 -- Submitted 20-Nov-2013 -- Reformatted slightly, wrapped lines, added references, adjusted the KDF [nickm] Summary: This is an attempt to translate the proposed circuit handshake from "Ace: An Efficient Key-Exchange Protocol for Onion Routing" by Backes, Kate, and Mohammadi into a Tor proposal format. The specification assumes an implementation of scalar multiplication and addition of two curve elements, as in Robert Ransom's celator library. Notation: Let a|b be the concatenation of a with b. Let H(x,t) be a tweakable hash function of output width H_LENGTH bytes. Let t_mac, t_key, and t_verify be a set of arbitrarily-chosen tweaks for the hash function. Let EXP(a,b) be a^b in some appropriate group G where the appropriate DH parameters hold. Let's say elements of this group, when represented as byte strings, are all G_LENGTH bytes long. Let's say we are using a generator g for this group. Let MUTLIEXPONEN (a,b,c,d) be (a^b)*(c^d) in some appropriate group G where the appropriate DH parameters hold. Let's say elements of this group, when represented as byte strings, are all G_LENGTH bytes long. Let's say we are using a generator g for this group. Let PROTOID be a string designating this variant of the protocol. Let KEYID be a collision-resistant (but not necessarily preimage-resistant) hash function on members of G, of output length H_LENGTH bytes. Instantiation: Let's call this PROTOID "ace-curve25519-ed-uncompressed-sha256-1" Set H(x,t) == HMAC_SHA256 with message x and key t. So H_LENGTH == 32. Set t_mac == PROTOID | ":mac" t_key == PROTOID | ":key" t_verify == PROTOID | ":verify" Set EXP(a,b) == scalar_mult_curve25519(a,b), MUTLIEXPONEN(a,b) == dblscalarmult_curve25519(a,b,c,d), and g == 9 . Set KEYID(B) == B. (We don't need to use a hash function here, since our keys are already very short. It is trivially collision-resistant, since KEYID(A)==KEYID(B) iff A==B.) Protocol: Take a router with identity key digest ID. As setup, the router generates a secret key b, and a public onion key B = EXP(g,b). The router publishes B in its server descriptor. To send a create cell, the client generates two keypairs of x_1, X_1=EXP(g,x_1) and x_2, X_2=EXP(g,x_2) and sends a CREATE cell with contents: NODEID: ID -- H_LENGTH bytes KEYID: KEYID(B) -- H_LENGTH bytes CLIENT_PK: X_1, X_2 -- 2 x G_LENGTH bytes The server checks X_1, X_2, generates a keypair of y, Y=EXP(g,y) and computes point = MUTLIEXPONEN(X_1,y,X_2,b) secret_input = point | ID | B | X_1 | X_2 | Y | PROTOID KEY_SEED = H(secret_input | "Key Seed", t_key) KEY_VERIFY = H(secret_input | "HMac Seed", t_verify) auth_input = ID | Y | X_1 | X_2 | PROTOID | "Server" The server sends a CREATED cell containing: SERVER_PK: Y -- G_LENGTH bytes AUTH: H(auth_input, KEY_VERIFY) -- H_LENGTH bytes The client then checks Y, and computes point = MUTLIEXPONEN(Y,x_1,B,x_2) secret_input = | ID | B | X_1 | X_2 | Y | PROTOID KEY_SEED = H(secret_input | "Key Seed", t_key) KEY_VERIFY = H(secret_input | "HMac Seed", t_verify) auth_input = ID | B | Y | X_1 | X_2 | PROTOID | "Server" The client verifies that AUTH == H(auth_input, KEY_VERIFY). Both parties now have a shared value for KEY_SEED. They expand this into the keys needed for the Tor relay protocol. Key expansion: When using this handshake, clients and servers should expand keys using HKDF as with the ntor handshake today. See also: http://www.infsec.cs.uni-saarland.de/~mohammadi/ace/ace.html for implementations, academic paper, and benchmarking code.

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Transport composition
by George Kadianakis 19 Nov '13

19 Nov '13

Hello Kevin, If you are interested in learning more about the transport combiner idea we were recently discussing, check out trac tickets #10061, #9744 and #7167. It would be awesome if you could comment with any ideas or criticisms you have. Cheers!

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Development Calendar
by Tom Lowenthal 18 Nov '13

18 Nov '13

Hello humans, I know that meetings and scheduling are a pain. That sucks. Here's a calendar of our regular meetings, which might make it easier: <https://www.google.com/calendar/embed?src=1gf7r9dh4bcv0vc926ipq5177g%40grou…> I hope that helps a bit. Here are some thoughts. It's a Google calendar. Yeah, about that. Calendars are hard, and I couldn't find anything free and open that seemed as easy and convenient as Google calendar. If you know of something FLOSS that's as easy and convenient, you should tell me, and help me move it over. In the mean time, you don't need a Google account to use it, and you can read it on the web or with an iCal feed. Complaints and suggestions welcome. Access/collaboration. I think you need a Google account to editing things. If you have a Google account and you want to edit this thing, drop me a line with a blurb and a Google account adress. I'll add you. If you don't have a Google account, fear not too hard. If you email me, I'll add something to the calendar for you. Here are things you should include in your email: * title for the event/meeting; * timezone, start, and end times; * location, IRC channel, phone access procedure, or whatever; * repeat schedule; * any content or description for the body; and * anything else you think is important. Updates. This calendar should remain accurate, especially for meetings which I plan or am at. I use it as *my* primary calendar of public Tor meetings, so it'll always represent my current view of the universe. Anything else? -Tom

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obfsproxy buffering
by David Stainton 18 Nov '13

18 Nov '13

Hi, I noticed that because the obfsproxy api can sometimes buffer and resend smaller chunks of data. My simple use of Nacl stream_crypto to wrap each incoming data buffers will not work... that is because the client and server must keep synchronized nonce counters for the decrypt/encrypt to work... and in this case the client may send one large buffer and the server may receive many smaller buffers... trying to decrypt them with different nonces will of course fail. https://github.com/david415/obfsproxy/tree/david-nacl-stream-withoutkeyexch… It seems like the solution is to write a super simple "framing protocol"... which is to say that I can first send a frame length; and on the receiving end simply read until frame length worth of data is consumed... and then apply the crypto_stream cipher on that frame with the correct corresponding nonce. David

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Speeding Up Tor with SPDY
by Christian Grothoff 18 Nov '13

18 Nov '13

Dear all, Andrey Uzunov's Master's thesis on "Speeding Up Tor with SPDY" is now available at https://gnunet.org/content/speeding-tor-spdy My personal conclusions are that SPDY PUSH should not be used with Tor, and that modest performance gains with SPDY are attainable for typical websites. Aside from deployment considerations (how to detect exits supporting SPDY2HTTP translation), a major area for further work will be adding HTTP pipelining support to the SPDY2HTTP proxy to avoid performance regressions seen with some sites. For those that prefer watching over reading, we'll post the defense talk on https://gnunet.org/ once we've finished the conversion. Feedback is of course welcome. However, as Andrey is now finished with his thesis and looking for work (hire him!) -- and as I don't have any funding to support further work on this now -- it is unlikely that we'll be doing any further major implementation work on this in the near future. Naturally, the existing code is freely available (and does work, if one is willing to go through the pains to set it up properly). Happy hacking! Christian

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Fwd: Stem Tor - Establish a user defined circuit
by Aravindan B 18 Nov '13

18 Nov '13

Hi all, Need some help in writing python script for establishing connection in stem tor using the method controller.new_circuit() or controller.extend_circuit() I tried this from stem import CircStatus from stem.control import Controller with Controller.from_port() as controller: controller.authenticate() relay_ip_addresses = ["10.0.0.21","10.0.0.22","10.0.0.23"] circuit_id = controller.extend_circuit('0',relay_ip_addresses) But i am getting Socket already closed exception. Am i right with the syntax of the same. The thing i am trying to achieve is that i want tor to choose the following ip addresses for 1. 10.0.0.21 for entry 2. 10.0.0.22 for middle nodes 3. 10.0.0.23 for exit nodes I need tor chose only these three ip nodes as the relay. I have to run this inside CORE Emulator to simulate TOR in CORE. Expecting a reply soon. Thanks in advance for the help. Thanks and regards Aravindan

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next globe update feedback
by me＠rndm.de 17 Nov '13

17 Nov '13

Hi there, I worked on a new update for globe. This update addresses some features that were missing or not possible in the current version of globe ( http://globe.rndm.de/ ). These changes include: - fixed minification process to allow usage of the ember production build - removed unnecessary whitespace on top of the page - modified loading indicator - added subpages Because this update includes some major ui changes, I would like to get some feedback on it. You find the latest version on http://globe.rndm.de/lab/ Cheers, Christian

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RecommendedTBBVersions
by Micah Lee 17 Nov '13

17 Nov '13

This URL has traditionally been a JSON string that lists the recommended version of TBB to install: https://check.torproject.org/RecommendedTBBVersions But the last couple days it's been returning 404. Did it move somewhere? Tor Browser Launcher uses it to figure out what version of TBB to download and install. Thanks! -- Micah Lee @micahflee

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