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Proposal xyz : Count Unique IP addresses in an anonymous way
by Jaskaran Singh 02 Apr '17

02 Apr '17

Hi, Please have a look at this proposal. Will replace xyz with more meaningful numbers once this is finalized. Comments, suggestions and criticism are welcome. ------------- Filename: xxx-Count-unique-IPs-in-anonymous-way.txt Title: Count Unique IP addresses in an anonymous way Author: Jaskaran Veer Singh Created: 14 March 2017 Status: Draft §0. Introduction Currently, guard relays and bridges maintains a list of IP addresses of the devices that connect to it for various reasons such as for use by the bridge to check which country has them blocked. This is dangerous because if any of these tor instances get compromised, clients will be de-anonymized. To solve this issue, a new data structure that keeps a track of unique IP addresses seen but does not directly keep a list of them is proposed in this document. §1. Specification §1.1. Notation Let `a^b` denote the exponentiation of a to the bth power. Let `a == b` denote the equality of a with b, and vice versa. Let `a := b` be the assignment of the value of b to the variable a. Let `a / b` denote the division of a by b. Let `a <= b` denote that a is less than equal to b. Let `a >= b` denote that a is greater than equal to b. §2. Research There are three ways to solve this problem. All the three ways are actually Big Data Algorithms. A few problems arises for each of these algorithms since they are made for big data but the data we would provide is not necessarily big. §2.1. Bloom Filter[1] A bloom filter maps the input to positions on the bitmap after passing through 2 or more hash functions. Later any new input are mapped onto this bitmap in the same way to check whether this value is already present in the set. The feature of this bitmap is that collisions could happen. And this collision creates deniability. When collisions happen, On the one hand, one of the input doesn’t count to be unique (although in reality, it is), and on the other hand, this is beneficial since this creates deniability. The person who gets hand on this data structure could never be 100% sure about the original inputs. So we get the job done successfully at some error rate. §3.1.1. Obstacle Suppose if the number of inputs is small. Let’s say we receive just 1 connection in a day from some small, less busy country like Estonia. In that case, there might not be any chance for collision and the adversary could determine the IP address with some brute force. Hence this algorithm isn’t suited for us. §3.2. Rappor[2] Randomized Aggregatable Privacy Preserving Ordinal Responses is an algorithm where the system adds some deterministic and nondeterministic noise to the data that has to be stored. This creates deniability. In our case, we don’t need to have deterministic noise added at first stage. So we’ll just stick to adding non deterministic noise and storing it in a bloom filter. One thing to note here is that, we should not accept output of the non deterministic randomizer which can be traced back to any IP address of Group D or Group E since those IP addresses are not in use and the adversary could easily know that those have been produced after adding random noise. §3.2.1. Obstacle Using brute force technique, the adversary could check to see whether the IP address stored is the correct one or produced using random noise. In this technique, the adversary could compare those IP address (obtained via brute force) to the directory of what IP addresses are allotted to what country. The one that does not match, is the one that has been faked by using random noise. §3.3. Probabilistic Counting with Stochastic Averaging[3] (PCSA) It is based on FM sketches. The algorithm goes as follows: | m = 2^b # with b in [4...16] | bitmaps = [[0]*32]*m # initialize m 32bit wide bitmaps to 0s | | # Construct the PCSA bitmaps | for h in hashed(data): | bitmap_index = 1 + get_bitmap_index( h,b ) # binary address of rightmost b bits | run_length = run_of_zeros( h,b ) # length of the run of zeros starting at bit b+1 | bitmaps[bitmap_index][run_length] = 1 # set the bitmap bit based on the run length observed | | # Determine the cardinality | phi = 0.77351 | DV = m / phi * 2 ^ (sum( least_sig_bit( bitmap ) ) / m) # the DV estimate So, Error is bounded by 0.78/sqrt(m) §3.3.1. Obstacle This algorithms stated above is made for use on large databases. Infact, these were invented to save time and space while doing basic set operations on data with high cardinality. But the data we would provide as an input is not necessarily of high cardinality. Since we would be counting numbers for each country separately, so the expected value of the input cardinality would be : 0 <= C <= 2500 where C is the actual cardinality of the input data. §3.3.2. Workaround As a workaround, we could introduce a correction term for small values of cardinality. So our final formula could look something like: DV(S1,...,Sm) := m· (2^(Z/m) −2^(−κ·Z/m))/ ρ Where Κ is chosen to be around 1.75 §4. Implementation The data structure present in the geoip.c needs to be removed as it stores the IP address of the client. The data structure is shown below. struct clientmap_entry_t { HT_ENTRY(clientmap_entry_t) node; tor_addr_t addr; char *transport_name; unsigned int last_seen_in_minutes:30; unsigned int action:2; }; It then later needs to be replaced by a datastruture that contains the list of countries with the number of unique IP addrs seen for that country. The whole system can be represented by this diagram. ------------------ | Input IP Addr | ------------------ | | --------------------- | Determine Country | --------------------- | | ---------------------- | Determine Transport| ---------------------- | | ------------------------------ | Get salted hash of IP addr | ------------------------------ | | -------------------------- | Apply the formula | | on the hash obtained | -------------------------- | | --------------------------------------- | Increment that country's counter | | if the cardinality estimation | | is greater than the estimation | | done previously | --------------------------------------- §5. Security Considerations We might as well go ahead and implement this, but the thing to keep in mind is that implementing this would not protect a client's identity from a adversary completely. First thing to understand is that, an adversary that has gained access to a guard node or a bridge could still get the random value generated and deanonymize the client using brute force. Or even better, why would the adversary need that random value when she simply log all network connections coming into the compromised system? So, A thing to note is that this functionality would keep those clients anonymous who had connected to the compromised system in the past, but not those who will connect to it in the future. §6. References [1] https://en.wikipedia.org/wiki/Bloom_filter [2] https://www.chromium.org/developers/design-documents/rappor [3] https://research.neustar.biz/2013/04/02/sketch-of-the- day-probabilistic-counting-with-stochastic-averaging-pcsa/ ------------- Regards, Jaskaran Veer Singh

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GSoC 17 | Name System API for Tor Onion Services
by Ivan Tham 01 Apr '17

01 Apr '17

I have created a proposal at http://dl.pickfire.tk/tor/proposal.md Feel free to review it and give comments, python script still WIP.

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[GSoC] Proposal for Ahmia - Hidden Service Search
by Pushkar Pathak 01 Apr '17

01 Apr '17

Hello everyone I am a third year undergrad at International Institute of Information Technology, Hyderabad. I have been working on Ahmia for some time now. There are several fixes and upgrades required in the codebase. Below is the list of tasks I plan to complete under GSoC17: - Automate Blacklisting of child abuse websites - Add Hidden Services page - Data visualization under statistics page. Examples include i) Linking structure between sites and keyword based labeling for onions in the graph. ii) Popularity of domains according to backlinks and search clicks - Replace Polipo with TorSocks5 for ahmia-crawler - Upgrade support from Elastic 2.4.0 to 5.X.X - Add advanced search options like operators for multiple search terms in a single query - Complete Documentation on ahmia.fi and Github page Details of the above tasks along with timeline and other relevant details are included in the proposal attached. You are welcome to comment on it and give your suggestions. Cheers, Pushkar Pathak Proposal for Tor Project: Ahmia - Hidden Servic... <https://docs.google.com/document/d/1h6ZbUMzKCkvyXQ9UTOy8nKVjV4fgps9UxTkBQCU…>

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[GSoC] Intro & Questions
by Mark Cohen 30 Mar '17

30 Mar '17

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Hello everyone! My name is Mark, and I'm a 2nd year undergraduate at UChicago, majoring in CS and math. I greatly admire the Tor community, and as a longtime user I've always wanted to give back. As far as relevant experience goes, I've taken courses in systems, networks, and languages, and I'm currently in a wonderful usable security course taught by Blase Ur. Last summer I worked for Keybase, which was both a lot of fun and highly educational. For GSoC, I'm most interested in helping improve the state of IPv6. I would love to pick someone's brain before creating an application to get a conceptual feel for the project and to learn about the kinds of things I'd be implementing. If you're that person, I'd really appreciate it if you could reach out either on here or via any other contact method (check my website linked below). Thanks for reading, and I'm looking forward to talking to you! ~Mark (https://mpcsh.xyz) -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEmyuHiWNRDa+IFK5Pss2qrTdc5gQFAljdV10ACgkQss2qrTdc 5gTWrw/+NpcZ/LahaxKXc3rdejLqblg8iiQVBxO8I7FkJkST5kz8gOFoheImrmSF gh2Jz/gY3TK/U8OXd8yDBPVd8KwWadCF161BURQtN8U35Rxao+Xmrrwhp5P2lj2L DfGkBwDzkIAOeCKOITh64guuzpPrhCWJOean7gJs6zHBIB+cIRZF1/3LhbtqRLJI nKcBy1mWjwHJ2CKkIhIFFHkY2WfqQ3JvlngjwDFUuYvBTrHKAKK1tl7Wnuo7npFs OZSaSxuXK4bQPGRINpQoPNyYI4sjKYQChco1ZLZ3v7Kc1Uyy0xlR5ittEl5GnaKl 4tXVRJpjDkkrWwHYxpVl5YrzUAC0OlJ9yh7qDZK2OQ5V6UEv+cpZJU5fGNrRKYxG JLMvs3Jf42xHIyMI0H7ya0Fh12PrOAD7en0mqM4Ie55/uvCb9FSbDhGOXvjuIIvp 2E6pJYsEXXvCZMyO8C36zEWn4JsEvAAAUeig9vyqL7kEDIL0vql5CwXO27MI3nqz IIk+ogVpITIooHB+owR01QENZ7DIoj1uRvX4skF+hXtA2W66J10Uw1b2gy2qPPbG HoAZW+nXRpKUYmWsvy8wwqZNtxdhZ8DgY78hXqrFOr65v9Odi6aNnAVSB9m9Dg4b Iu6LW7jbOOYbT6ZUWB7XwG7qi+jtHAzZZ7ZOAVzU37cyzGf2tnY= =eUZ0 -----END PGP SIGNATURE-----

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GSoC 2017 - Questions
by Krishna Shukla 30 Mar '17

30 Mar '17

Hey, I'm Krishna Shukla, I'm studying a bachelors of computer science at the University of Queensland. I guess the relevant subjects I've studied so far covers C and Unix programming, Computer Networks, Algorithms and Data Structures, and Programming in the large. (got a high distinction in all the above) My most important question is if I could work on a project but not actually be apart of GSoC? - I am unfortunately ineligible as my brother works as a Security Engineer at Google Sydney. And if the above is okay would it also be okay to not have to strictly abide by their timeline as I don't actually have holidays during this time in Australia but I'd like to contribute in my free time nonetheless! As for projects themselves I'm really interested in the relay crypto parallelism and the hidden service crypto parallelism. And I have a couple of questions regarding them. For the relay crypto parallelism I wanted to know what is there left to be done? When I looked at the tickey #1749 someone called towelenee made a few patches that already made it multi threaded, were these changes just not accepted? Also wanted to know if specific knowledge about circuit cryptography was required? As I know of it, but I certainly cannot make my own fully homomorphic cryptosystem, is it more in the steps of the system has already been made, it just needs to be parallelised correctly? It also states the code is written to expect immediate responses, I'm not sure what you mean by that, after all there is always a slight delay, and if it becomes multi threaded we can never know what is running what when, so is it more someone is waiting at the other end of a socket and needs it ASAP, or is it internally things want the answer quickly (in which case I don't know how to solve it other than uses mutexes which is probably not so okay)? I am interested in the hidden service crypto parallelism in its own right, but I was also thinking weather it would be a feasible idea to combine the two projects and create a multi-threaded decryption library that could be linked to both the tor relay and the hidden services (could release it as a cryptosystem library, all the fully homorphic cryptosystem libraries I found used GPL licenses and thus not compatible with tors), or are their requirements too far apart? Also I was wondering how the Ahmia automated blacklisting was planned to work? As in how would a list of child abuse sites be fetched? Honestly I don't actually know python, I've worked with it and Django before in a hackathon once, but I cannot claim any real knowledge in it, but at the same time I am passionate about the topic of child abuse, and I think if I can help reduce its demand in anyway by making it harder to find, I'd say it's some good added to the world. Apologies about the long mail guys, Krishna Shukla

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GSOC 2017: Proposal for anon-connection-wizard
by irykoon 29 Mar '17

29 Mar '17

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Hello everyone! The following is my first draft of the proposal for the anon-connection-wizard. Could anyone offer me some feedback about it please? Any recommendation, suggestion and criticism are very welcome and appreciated! > # Introduction > > Every software project should solve a problem. Before offering the > solution (your Google Summer of Code project), you should first > define the problem. What’s the current state of things? What’s the > issue you wish to solve and why? Then you should conclude with a > sentence or two about your solution. Include links to discussions, > features, or bugs that describe the problem further if necessary. The anon-connection-wizard is a Python-clone of the Tor Launcher which aims at providing Tor users with a graphical instruction on configuring the Tor. This applicatipn has been developed as a part of the Whonix Project: https://github.com/Whonix/anon-connection-wizard Some of the screenshots of the old version anon-connection-wizard can be found here: https://www.whonix.org/blog/connection-bridge-wizard This application is especially helpful for users who live in Tor-censored area. This is because those users can only connect to the Tor network with the help of other censorship circumvention tools which include but are not limited to Tor bridges, pluggable transports and other third party Internet censorship circumvention tools like Lantern and VPN. Currently, the Tor Launcher is shipped with the Tor Browser Bundle and heavily relies on the Tor Browser for its implementation. These facts cause using Tor Launcher without having the Tor Browser impossible. I agree with the whonix core developer Patrick Schleizer that "the Tor Browser Bundle has its kind of users. system Tor (refers to Tor from packages.debian.org or deb.torproject.org) users, where Tor runs as daemon, is used in different ways for different purposes. These users cannot use Tor Launcher, because it only works with Tor Browser". Therefore, although anon-connection-wizard is a Python-clone of the Tor luancher, since all its dependencies are already in Debian and alrea dy packaged, it can still be really useful for the system Tor users. In addition, the current instructions provided by the anon-connection-wizard and Tor launcher is not be clear enough for user to configure Tor correctly. Therefore I would like to implement and redesign the anon-connection-wizard. I hope that my work will help more people to connect to the Tor network efficiently and successfully. > # Project goals > > Be short and to the point, and perhaps format it as a list. > Propose a clear list of deliverables, explaining exactly what you > promise to do and what you do not plan to do. “Future developments” > can be mentioned, but your promise for the Google Summer of Code > term is what counts. As mentioned above, the projects goals include two main parts: 1. The clone implementation of Tor Launcher; 2. The redesign of the anon-connection-wizard. > # Implementation > > Be detailed. Describe what you plan to do as a solution for the > problem you defined above. Include technical details, showing that > you understand the technology. Illustrate key technical elements > of your proposed solution in reasonable detail. > The clone implementation of Tor Launcher: Currently, I have helped to implement the basic functions of anon-connection-wizard. However, there are still several bugs need fixing and a large number of exciting features need implementing, which include: 1. The current implementation of configuring torrc file is very rudimentary. The anon-connection-wizard should read the previous bridge/proxy configuration from the file and adjust the default UI accordingly. Just like what Tor Launcher has been doing. The "edit marker approach" is preferred way to implement this: https://forums.whonix.org/t/graphical-gui-whonix-setup-wizard-anon-conne ction-wizard-technical-discussion/650/226 2. The password for proxy setting should be covered by character * The redesign of the anon-connection-wizard: I have made a specific proposal for this topic, which can be found here: https://forums.whonix.org/t/a-proposal-for-redesigning-anon-connection-w izard-for-better-usability/3681 The redesign should at least includes: 1. Rearranging the instruction page orders for better usability; 2. Rewriting the literal instruction so that it fits the actual situation of people in censored areas; 3. Adding more features to the custom Tor bridges configuration input box for more clear instruction. For example, syntax highlight, tool-tips, etc; 4. Doing user behavior experiment to find out what can be helpful for better usability; 5. Modifying the anon-connection-wizard based on the result of the experiment. > # Timeline > > Show that you understand the problem, have a solution, have also > broken it down into manageable parts, and that you have a > realistic plan on how to accomplish your goal. Here you set expectations, so don’t make promises you can’t keep. A modest, realistic and detailed timeline is better than promising the impossible. Since the specific dates may be changed with the undecided working schedule. I arrange my timeline in a week unit. Week 1: The password for proxy setting should be covered by character *. Week 2: Implement the "edit marker approach". Week 3: Rewriting the literal instruction so that it fits the actual situation of people in censored areas. Week 4: Generate ideas on redesigning the anon-continence-wizard users interface, basing on the recommendations from outside sources, problems discussed above and suggestions from other people. Present the planning redesign to public to receive feedback. Week 5: Rearranging the instruction page orders for better usability; Rewriting the literal instruction so that it fits the actual situation of people in censored areas. Week 6: Adding more features to the custom Tor bridges configuration input box for more clear instruction. For example, syntax highlight, tool-tips, et c; Week 7: Prepare for the user behavior experiment, including recruitment and setting up environment. Week 8: Conduct the experiment. Week 9: Process and analysis the experiment data. Week 10: Write the research report. Week 11: Modifying the anon-connection-wizard based on the result of the experiment. Week 12: Modifying the anon-connection-wizard based on the result of the experiment. > > If you have other commitments during GSoC, such as a job, > vacation, exams, internship, seminars, or papers to write, disclose > them here. I am going to be enrolled for the Summer 2017 semester that begins May 22nd and ends June 23th at XXX University. I am going to take two classes from Monday to Friday for each week during the Summer semester. One will be from 3:20PM to 5:00PM (UTC) and another one will be from 7:00PM to 8:40PM (UTC). > GSoC should be treated like a full-time job, and we will expect > approximately 40 hours of work per week. If you have conflicts, > explain how you will work around them. If you are found to have > conflicts which you did not disclose, you may be failed. The sum of the time I will be in class for each weekday will be 3 hours and 20 minute which is totally fine to me. My current overall GPA is 4.0/4.0 which may help to prove I can handle my school study well. According to Google Summer of Code timeline, the “[c]oding officially begins” at May 30th which means there will be approximate three weeks that I have both school study and Google Summer of Code. To work around it, I have came up with three plans which either of them is fine to my potential mentor: 1. Since I have been familiar with the contributing workflow for Whonix, I do not have to spend a lot of time to get used to it. Therefore I can use the “Community Bonding Period” which is from May 4th to May 30th to do the real coding for the project; 2. I can also keep committing to the project during each weekend from now on before May 4th . This is also a way to work around the time conflicts. 3. If I am expected to code only during the official timeline, I can spend 5 hours each day during the weekdays and spend 8 hours each day during the weekends. > Open and clear communication is of utmost importance. Include your > plans for communication in your proposal; daily if possible. I agree that “[o]pen and clear communication is of utmost importance”. This is because of two main reasons from my point of view. First, a successful free and open source software development heavily relies on the collaboration between different people. A good communication skill will create a positive and supportive atmosphere which not only make everyone works for it more efficient but also attracts more people to join the development. Second, feedback from others, especially mentor, can be extremely beneficial to a student’s progress. Without the feedback, it may take a student years until one day after a frustrating debugging process to realize a mistake he/she made; while he/she may realize several mistakes he/she made almost immediately from his/her mentor’s feedback. I have already been working on the project with my potential mentor Patrick Schleizer. A small part of our open communication can be found [here](https://forums.whonix.org/t/graphical-gui-whonix-setup-wizard-ano n-connection-wizard-technical-discussion/650/222), which may be helpful to prove we have been having an open and clear communication. My plan is to take the [Whonix Forum](https://forums.whonix.org/) as the daily communication platform with my potential mentor Patrick. And just like what I have been doing, I will also post a detailed progress report for each working period which is no more than a week. I can definitely send the posts to the tor-dev mailing list if it is considered as a good idea. > # About me > > Provide your contact information Currently, people can contact me through the following ways: 1. Email: irykoon at gmail dot com GPG: https://pgp.mit.edu/pks/lookup?op=vindex&search=0xA14B4DBC6DCDD53C 2. Github: @irykoon 3. Whonix Forum: @iry I will inform the public if there is any change to my contact informatio n. > and write a few sentences about you and why you think you are the > best for this job. As one who was living in oppressive area, I deeply understand the importance of Internet freedom to a society. At first, I merely considered Internet freedom as fighting against Internet censorship. However, after a large amount of observation, reading and reflection, I realized that the self-censorship conducted by every scared citizens was much more powerful and terrible than the censorship conducted by the outside world. It was at that moment I realized the online anonymity was a vital component to Internet freedom because it frees people from fear. I value Tor/Whonix. Without it, I couldn't have been freed from the fear and explored the world freely and finally became who I am today. Therefore, contributing to Tor/Whonix as a career is not only a dream that I have been fighting for, but also an essential approach to my self-actualization. > Prior contributions are helpful; list your commits. The followings are my pull requests on GitHub to the Whonix: 1. [Basic features implementation](https://github.com/Whonix/anon-connection-wizard/pull/1) 2. [Pluggable transport renew](https://github.com/Whonix/anon-connection-wizard/pull/2) 3. [A proposal for redesigning anon-connection-wizard for better usability](https://github.com/Whonix/anon-connection-wizard/pull/3) 4. [Port from Python2 to Python3.4 & from PyQt4 to PyQt5](https://github.com/Whonix/anon-connection-wizard/pull/4) The following is my proposal for the redesign of anon-connection-wizard: 1. https://forums.whonix.org/t/a-proposal-for-redesigning-anon-connection-w izard-for-better-usability/3681 > Name people (other developers, students, professors) who can act > as a reference for you. Mention your field of study if necessary. My potential mentor, Patrick Schleizer, can be a reference for me. He is a core developer of the Whonix Project, > Other things to think about: * Are you comfortable working > independently under a supervisor or mentor who is several thousand > miles away, and perhaps 12 time zones away? How will you work with > your mentor to track your work? Have you worked in this style > before? Yes! I have been interacting, working and learning in this style with my potential mentor and I am really comfortable with that. > * If your native language is not English, are you comfortable > working closely with a supervisor whose native language is > English? What is your native language, as that may help us find a > mentor who has the same native language? Both my potential mentor Patrick and I can communicate in English. So there is no problem with that. -----BEGIN PGP SIGNATURE----- iQIcBAEBCgAGBQJY1r/pAAoJEKFLTbxtzdU8wFsP/A2FwFd5Yg+9m6nKlgcywA9x HNGuAc9RRyRg6MiOqg25NJdcDpa6d7y6wy5dBqXKjn5yWvcogQrFrONWXl9/U3D2 DwTCITF2EyDrLH/t9oUCFsE169oZSZ02WdqgCdl4yVF1Bdxk8lMW0/raZ325rTxH QMv4ueG2YacVQ88vDxaY9wY9CAoghAvR+zjp9M3Lu0iebH4ZDfBaH19RZjWUa/+Y eyvjY5DyFp74rct4UYX+Rqnqlgf8meTSoKAAJ4cbWPncQyIvWjVrzY3RTmznSg95 Dh97RJ3Ufso2h73dlUnojuLADOFEyyrL1hgNpqf7RAUhR5Dc+xTvwSmuqss9D8dQ hjANF9ZpADcdDAQGSbcxlUcdd7u1twvVPnstlTLHsdLxbMS8F16SZhUAjJMlwOua bdxssBGsdoht0fJmSB4LHz4G6r6cOlo2nRFD5Noo3rk63buS/+h8/zPBlOXsS8Ox PNAKnUHkTQYucjmERlz7XwKFccoJNhO2Iha8hA3WkMwsTKzkbkJtRUX+NjE1XLrA 3ITVrzT08Bd5IpLrIKa352sknoqzv+/L0tVxdHc1xkjx0XgacHXLD3UcX1Zff/0p QVKuE/PmavJinRbYh/g1mMZoZVryLRTsn/wOMKRoCmL+/xbIJIyM/IBEqxMyBFuU SHq1QajHPvncx/dttM3W =FRpt -----END PGP SIGNATURE-----

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GSoC 17 | Name System API for Tor Onion Services
by Pickfire 29 Mar '17

29 Mar '17

Hi, I am Ivan Tham. Currently studying in Computer Science in APIIT Malaysia. I am interested particapate in Google Summer of Code 2017 under tor organization. I am interested to see Proposal 224 coming along but I would really like to see [Proposal 272][0] and hope that tor hidden services can be more user-friendly. What do you think of the projects? Is the proposal too immature? I had looked into [OnioNS][1] as well and like the idea of having different types of DNS records for tor hidden services, how does it integrate with [Proposal 272][0]? [0]: https://lists.torproject.org/pipermail/tor-dev/2016-October/011524.html [1]: https://lists.torproject.org/pipermail/tor-dev/2015-May/008826.html

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Issues With Ticket #7532 - "Count unique IPs in an anonymous way"
by samir menon 28 Mar '17

28 Mar '17

This ticket [1] was suggested as a GSoC project, but I think there might be an issue with the security model/perceived threat. To summarize the ticket and its child [1], basically, we currently store all the IP's seen by a node so that we can count unique IP's. The idea is that this is dangerous; if a node is compromised, then all of those IP addresses can be retrieved from memory. Therefore, a variety of mitigation methods have been proposed (most prominently, the 'Probabilistic Counting Algorithm' from [2]) Here's my issue: what about brute force? No matter what method we use, we will arrive at a data structure that should be able to, given an IP address, tell us whether it is new (and we should increment the unique counter) or old (and we should leave the unique counter the same), with some reasonably small false positive rate. Basically, we're supposed to use some kind of Bloom filter like structure. Then can't that structure then be brute-forced, offline, by an attacker? IPv4 addresses are 32-bits (~4.3 billion of them), so an attacker could just run whatever method we use to check membership over and over, and then recover the set of IP's. The same happens if we hash the IP's beforehand. So, is this attack acceptable? The only mitigation I've seen is the one referenced by 'Aaron' in the ticket, which is the system that git uses, cryptolog; there, they have a random salt that changes daily. Then, an attacker can only learn the IP's for one day. This sounds like a reasonable compromise to me, but then the implementation becomes rather simple; just hash the IP's with a random salt that changes daily before putting them in the set. IPv6 also solves this (128 bits), but there again, the solution is just to hash the IP's before storing them - the Bloom filter/'Probabilistic Counting Algorithm' is unnecessary. I think I must be missing something about how the 'Probabilistic Counting Algorithm' works - somehow, it needs to keep track of the # of unique IP's without knowing (with a high probability) whether any 1 individual IP has been seen. Any help/pointing out of errors in my reasoning would be useful. Thanks, Samir Menon menon.samir(a)gmail.com samir2(a)stanford.edu [1] https://trac.torproject.org/projects/tor/ticket/7532 [2] http://www.mathcs.emory.edu/~cheung/papers/StreamDB/Probab/1985-Flajolet-Pr…

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[RFC] Proposal for the encoding of prop224 onion addresses
by George Kadianakis 28 Mar '17

28 Mar '17

Hello list, we've had discussions over the past years about how to encode prop224 onion addresses. Here is the latest thread: https://lists.torproject.org/pipermail/tor-dev/2016-December/011734.html Bikeshedding is over; it's time to finally pick a scheme! My suggested scheme basically follows from the discussion on that thread, and is heavily based on the Bitcoin address format: https://en.bitcoin.it/wiki/Base58Check_encoding https://en.bitcoin.it/wiki/Technical_background_of_version_1_Bitcoin_addres… Here is the suggested scheme: onion_address = base32(version + pubkey + checksum) checksum = SHA3(".onion checksum" + version + pubkey) where: pubkey is 32 bytes (ed25519) version is one byte checksum is _truncated_ to two bytes With the above construction onion_address ends up being 56 bytes long (excluding the ".onion"): tbi5tdxbosiotphawjyu7f5pw5tlnvbvfjrj7meskbsnwr2bqbu2t4gg.onion tcrdnadkefvbdm3u56kz6lfh6v5lr24fpog5vzsy4n3djr2ymueu34ws.onion tcdw7lwmtp5pbwj2w7wf6amxdhmc62qitj2teu376r5s2fqke4r3uiq6.onion If people like the above suggestion, I will take the effort to engrave it in prop224. Here is the discussion section. Please provide feedback! [D1] How to use version field: The version field is one byte long. If we use it as an integer we can encode 256 values in it; if we use it as a bitmap we could encode properties and such. My suggestion is to simply use it as an integer like Bitcoin does. So we can assign value \x01 to normal onion services, and in the future we can assign more version tags if we need to. For example, we can give a different version field to onion services in the testnet. We can also reserve a range of values for application-specific purposes. [D1.1] Default version value: The next question is what version value to assign to normal onion services. In the above scheme where: onion_address = base32(version + pubkey + checksum) the value of 'version' basically determines the first two characters of the onion address. In Bitcoin, they've made it such that the default version value basically prefixes addresses with "1"; so all normal Bitcoin addresses start with 1 as in 14tDWDT9zqDufWZmiLqoaT9qJyHi7RRZPE What should we do in Tor? My suggestion is to use '\x98' as the default version value which prefixes all addresses with 't' (as in Tor). Check the examples I cited above. An alternative is to turn the scheme to: onion_address = base32(pubkey + checksum + version) where the version byte is at the end with no effect at usability. A heavier alternative would be to have two bytes of version so that we can just prefix them all with 'tor'... [D2] Checksum strength: In the suggested scheme we use a hash-based checksum of two bytes (16 bits). This means that in case of an address typo, we have 1/65536 probability to not detect the error (false negative). It also means that after 256 typos we will have 50% probability to miss an error (happy birthday!). I feel like the above numbers are pretty good given the small checksum size. The alternative would be to make the checksum four bytes (like in Bitcoin). This would _greatly_ increase the strength of our checksum but it would also increase our address length by 4 base32 characters (and also force us to remove leading padding from base32 output). This is how these 60-character addresses look like: tc2dty3zowj6oyhbyb5n3a2h3luztlx22hy2cwdvn37omsv7quy7rxiysn3a.onion tbdczrndtadzdhb6iyemnxf7f4i6x7yojnunarlrvt2virtmrecmwgx5golq.onion tc6pcgyorusw3jj5tosxakmcwfmcend2q4g2qnbjtkhuuh4dcgvs4rl4rdaa.onion You probably don't notice the size difference compared to the 56-character addresses, which perhaps is an argument for adopting a four byte checksum. Let me know what you think about this. [D3] Do we like base32??? In this proposal I suggest we keep the base32 encoding since we've been using it for a while; but this is the perfect time to switch if we feel the need to. For example, Bitcoin is using base58 which is much more compact than base32, and also has much better UX properties than base64: https://en.bitcoin.it/wiki/Base58Check_encoding#Background If we wanted to get a more compact encoding, we could adopt base58 or make our own adaptation of it. In this proposal I'm using base32 for everything, but I could be persuaded that now is the time to use a better encoding. Let me know what you think! Thanks :)

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Pluggable Transports 2.0, draft 1 Specification
by Brandon Wiley 28 Mar '17

28 Mar '17

As was discussed in the Pluggable Transports session at TorDev Amsterdam, the Pluggable Transports 2.0, draft 1 specification [https://www. pluggabletransports.info/spec/pt2draft1] was created by a committee of censorship circumvention tool developers: Tor, Lantern, Psiphon, and uProxy. It specifies a version of Pluggable Transports that meets the needs of multiple circumvention tools. There is one major change that has implications for tor, which is that the Pluggable Transports 2.0, draft 1 IPC protocol uses a different type of SOCKS authentication mechanism, which allows for larger parameters to be send to transports. We are currently working on a 2nd draft of this specification, which will incorporate changes and errata from the community censorship circumvention tool community. For instance, syntactic errors in the documentation of the Go interface will be fixed in draft 2. Tor developers participated in the specification meetings, and now feedback from the overall Tor community is requested for incorporation in the next draft. There will also likely be a 2.1 specification process, possibility starting August, where we will consider larger changes.

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