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Proposal 280: Privacy-Preseving Statistics with Privcount in Tor
by Nick Mathewson 13 Sep '17

13 Sep '17

Hi! Tim helped me write this this draft last week, and I shared it with the PrivCount authors. I've already gotten some good comments from Aaron, which I'll repost in a followup message, with his permission. ================================ Filename: 280-privcount-in-tor.txt Title: Privacy-Preseving Statistics with Privcount in Tor Author: Nick Mathewson, Tim Wilson-Brown Created: 02-Aug-2017 Status: Draft 0. Acknowledgments Tariq Elahi, George Danezis, and Ian Goldberg designed and implemented the PrivEx blinding scheme. Rob Jansen and Aaron Johnson extended PrivEx's differential privacy guarantees to multiple counters in PrivCount: https://github.com/privcount/privcount/blob/master/README.markdown#research… Rob Jansen and Tim Wilson-Brown wrote the majority of the experimental PrivCount code, based on the PrivEx secret-sharing variant. This implementation includes contributions from the PrivEx authors, and others: https://github.com/privcount/privcount/blob/master/CONTRIBUTORS.markdown 1. Introduction and scope PrivCount is a privacy-preserving way to collect aggregate statistics about the Tor network without exposing the statistics from any single Tor relay. This document describes the behavior of the in-Tor portion of the PrivCount system. It DOES NOT describe the counter configurations, or any other parts of the system. (These will be covered in separate proposals.) 2. PrivCount overview Here follows an oversimplified summary of PrivCount, with enough information to explain the Tor side of things. The actual operation of the non-Tor components is trickier than described below. All values in the scheme below are 64-bit unsigned integers; addition and subtraction are modulo 2^64. In PrivCount, a Data Collector (in this case a Tor relay) shares numeric data with N different Tally Reporters. (A Tally Reporter performs the summing and unblinding roles of the Tally Server and Share Keeper from experimental PrivCount.) All N Tally Reporters together can reconstruct the original data, but no (N-1)-sized subset of the Tally Reporters can learn anything about the data. (In reality, the Tally Reporters don't reconstruct the original data at all! Instead, they will reconstruct a _sum_ of the original data across all participating relays.) To share data, for each value X to be shared, the relay generates random values B_1 though B_n, and shares each B_i secretly with a single Tally Reporter. The relay then publishes Y = X + SUM(B_i) + Z, where Z is a noise value taken at random from a gaussian distribution. The Tally Reporters can reconstruct X+Z by securely computing SUM(B_i) across all contributing Data Collectors. (Tally Reporters MUST NOT share individual B_i values: that would expose the underlying relay totals.) In order to prevent bogus data from corrupting the tally, the Tor relays and the Tally Reporters perform multiple "instances" of this algorithm, randomly sampling in each relays. The relay sends multiple Y values for each measurement, built with different sets of B_i. These "instances" are numbered in order from 1 to R. So that the system will still produce results in the event of a single Tally Reporter failure, these instances are distributed across multiple subsets of Tally Reporters. Below we describe a data format for this. 3. The document format This document format builds on the line-based directory format used for other tor documents, described in Tor's dir-spec.txt. Using this format, we describe two kinds of documents here: a "counters" document that publishes all the Y values, and a "blinding" document that describes the B_i values. But see "An optimized alternative" below. The "counters" document has these elements: "privctr-dump-format" SP VERSION SP SigningKey [At start, exactly once] Describes the version of the dump format, and provides an ed25519 signing key to identify the relay. The signing key is encoded in base64 with padding stripped. VERSION is "alpha" now, but should be "1" once this document is finalized. [[[TODO: Do we need a counter version as well? Noise is distributed across a particular set of counters, to provide differential privacy guarantees for those counters. Reducing noise requires a break in the collection. Adding counters is ok if the noise on each counter monotonically increases. (Removing counters always reduces noise.) We also need to work out how to handle instances with mixed Tor versions, where some Data Collectors report different counters to other Data Collectors. (The blinding works if we substitute zeroes for missing counters on Tally Reporters. But we also need to add noise in this case.) -teor ]]] "starting-at" SP IsoTime [Exactly once] The start of the time period when the statistics here were collected. "ending-at" SP IsoTime [Exactly once] The end of the time period when the statistics here were collected. "num-instances" SP Number [Exactly once] The number of "instances" that the relay used (see above.) "tally-reporter" SP Identifier SP Key SP InstanceNumbers [At least twice] The curve25519 public key of each Tally Reporter that the relay believes in. (If the list does not match the list of participating tally reporters, they won't be able to find the relay's values correctly.) The identifiers are non-space, non-nul character sequences. The Key values are encoded in base64 with padding stripped; they must be unique within each counters document. The InstanceNumbers are comma-separated lists of decimal integers from 0 to (num-instances - 1), in ascending order. Keyword ":" SP Int SP Int SP Int ... [Any number of times] The Y values for a single measurement. There are num-instances such Y values for each measurement. They are 64-bit unsigned integers, expressed in decimal. The "Keyword" denotes which measurement is being shared. Keyword MAY be any sequence of characters other than colon, nul, space, and newline, though implementators SHOULD avoid getting too creative here. Keywords MUST be unique within a single document. Tally Reporters MUST handle unrecognized keywords. Keywords MAY appear in any order. It is safe to send the blinded totals for each instance to every Tally Reporter. To unblind the totals, a Tally Reporter needs: * a blinding document from each relay in the instance, and * the per-counter blinding sums from the other Tally Reporters in their instance. [[[TODO: But is it safer to create a per-instance counters document? -- teor]]] The semantics of individual measurements are not specified here. "signature" SP Signature [At end, exactly once] The Ed25519 signature of all the fields in the document, from the first byte, up to but not including the "signature" keyword here. The signature is encoded in base64 with padding stripped. The "blinding" document has these elements: "privctr-secret-offsets" SP VERSION SP SigningKey [At start, exactly once.] The VERSION and SigningKey parameters are the same as for "privctr-dump-format". "instances" SP Numbers [Exactly once] The instances that this Tally Reporter handles. They are given as comma-separated decimal integers, as in the "tally-reporter" entry in the counters document. They MUST match the instances listed in the counters document. [[[TODO: this is redundant. Specify the constraint instead? --teor]]] "num-counters" SP Number [Exactly once] The number of counters that the relay used in its counters document. This MUST be equal to the number of keywords in the counters document. [[[TODO: this is redundant. Specify the constraint instead? --teor]]] "tally-reporter-pubkey" SP Key [Exactly once] The curve25519 public key of the tally reporter who is intended to receive an decrypt this document. The key is base64-encoded with padding stripped. "count-document-digest" SP "sha3" Digest NL "-----BEGIN ENCRYPTED DATA-----" NL Data "-----END ENCRYPTED DATA-----" NL [Exactly once] The SHA3-256 digest of the count document corresponding to this blinding document. The digest is base64-encoded with padding stripped. The data encodes the blinding values (See "The Blinding Values") below, and is encrypted to the tally reporter's public key using the hybrid encryption algorithm described below. "signature" SP Signature [At end, exactly once] The Ed25519 signature of all the fields in the document, from the first byte, up to but not including the "signature" keyword here. The signature is encoded in base64 with padding stripped. 4. The Blinding Values The "Data" field of the blinding documents above, when decrypted, yields a sequence of 64-bit binary values, encoded in network (big-endian) order. There are C * R such values, where C is the number of keywords in the count document, and R is the number of instances that the Tally Reporter participates in. The client generates all of these values uniformly at random. For each keyword in the count document, in the order specified by the count document, the decrypted data holds R*8 bytes for the specified instance of that keyword's blinded counter. For example: if the count document lists the keywords "b", "x", "g", and "a" (in that order), and lists instances "0", and "2", then the decrypted data will hold the blinding values in this order: b, instance 0 b, instance 2 x, instance 0 x, instance 2 g, instance 0 g, instance 2 a, instance 0 a, instance 2 4. Implementation Notes A relay should, when starting a new round, generate all the blinding values and noise values in advance. The relay should then use these values to compute Y_0 = SUM(B_i) + Z for each instance of each counter. Having done this, the relay MUST encrypt the blinding values to the public key of each tally reporter, and wipe them from memory. 5. The hybrid encryption algorithm We use a hybrid encryption scheme above, where items can be encrypted to a public key. We instantiate it as follows, using curve25519 public keys. To encrypt a plaintext M to a public key PK1 1. the sender generates a new ephemeral keypair sk2, PK2. 2. The sender computes the shared diffie hellman secret SEED = (sk2 * PK1). 3. The sender derives 64 bytes of key material as SHAKE256(TEXT | SEED)[...64] where "TEXT" is "Expand curve25519 for privcount encryption". The first 32 bytes of this is an aes key K1; the second 32 bytes are a mac key K2. 4. The sender computes a ciphertext C as AES256_CTR(K1, M) 5. The sender computes a MAC as SHA3_256([00 00 00 00 00 00 00 20] | K2 | C) 6. The hybrid-encrypted text is PK2 | MAC | C. 6. An optimized alternative As an alternative, the sequences of blinding values is NOT transmitted to the tally reporters. Instead the client generates a single ephemeral keypair sk_c, PK_c, and places the public key in its counts document. It does this each time a new round begins. For each tally reporter with public key PK_i, the client then does the handshake sk_c * PK_i to compute SEED_i. The client then generates the blinding values for that tally reporter as SHAKE256(SEED_i)[...R*C*8]. After initializing the counters to Y_0, the client can discard the blinding values and sk_c. Later, the tally reporters can reconstruct the blinding values as SHAKE256(sk_i * PK_c)[...] This alternative allows the client to transmit only a single public key, when previously it would need to transmit a complete set of blinding factors for each tally reporter. Further, the alternative does away with the need for blinding documents altogether. It is, however, more sensitive to any defects in SHAKE256 than the design above. Like the rest of this design, it would need rethinking if we want to expand this scheme to work with anonymous data collectors, such as Tor clients.

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Proposal 282: Remove "Named" and "Unnamed" handling from consensus voting
by Nick Mathewson 12 Sep '17

12 Sep '17

Filename: 282-remove-named-from-consensus.txt Title: Remove "Named" and "Unnamed" handling from consensus voting Author: Nick Mathewson Created: 12-Sep-2017 Status: Open Target: 0.3.3.x 1. Summary Authorities no longer vote for the "Named" and "Unnamed" flags, and we have begun to remove the client code that supports them. (See proposal 235). The next logical step is to remove the special handling from these flags from the consensus voting algorithm. We specify this here. 2. Proposal We add a new consensus method, here represented as M, to be allocated when this proposal's implementation is merged. We specify that the Named and Unnamed flags are only handled specially when the negotiated consensus method is earlier than M. If the negotiated method is M or later, then the Named and Unnamed flags are handled as if any they were any other consensus flags.

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Help us build Tails 3.2~alpha1 build reproducibly
by anonym 08 Sep '17

08 Sep '17

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Dear Tails and Tor contributors, dear Reproducible Builds community, We have sent out a first call [1] for testing to build Tails 3.1 reproducibly and we have received some build reports. Thank you very much for your help! We have since then tried to fix most of the identified issues [2] in Tails 3.2~alpha1, and thus we'd kindly like to ask you to try to build the new ISO image again, or even for the first time. Please don't hesitate to contact us if you get stuck at some point in the process, for example by connecting to our chatroom [3]! You can also send us email to tails-dev at boum.org (public) or tails at boum.org (private). Note that Tails 3.2~alpha1 is *not* recommended for real usage, since it has not gone through *any* QA. Please use Tails 3.1 instead until Tails 3.2 is released! # How? For your convenience all instructions needed to attempt to reproduce Tails 3.2~alpha1 are included hereafter. However all commands are adapted for Debian Stretch (and Buster/Sid), so your results may vary if you run another Linux distribution. Our full build instructions [4] might help if you are having problems. ## Setup the build environment Building Tails requires the KVM virtual machine hypervisor to be available, a minimum of 1 GiB of free RAM and a maximum of 20 GB of free storage. ### Install dependencies sudo apt-get install \ git \ rake \ libvirt-daemon-system \ dnsmasq-base \ ebtables \ qemu-system-x86 \ qemu-utils \ vagrant \ vagrant-libvirt \ vmdebootstrap && \ sudo systemctl restart libvirtd ### If building as a non-root user (Skip this section if you intend to build Tails as the root user!) Make sure that the user that is supposed to initiate the build is part of the relevant groups: for group in kvm libvirt libvirt-qemu; do sudo adduser $user $group; done Then run `newgrp` (or just reboot) to apply the new group memberships to the session. ## Build Tails 3.2~alpha1 git clone https://git-tails.immerda.ch/tails cd tails git checkout 3.2~alpha1 git submodule update --init rake build # Send us feedback! No matter how your build attempt turned out we are interested in you sending us feedback. For that we'll first need some information of the system you used -- please run these commands in the exact same terminal session that you ran `rake build` in (e.g. run them right after `rake build`)! sudo apt install apt-show-versions || : ( for f in /etc/issue /proc/cpuinfo do echo "--- File: ${f} ---" cat "${f}" echo done for c in free locale env 'uname -a' '/usr/sbin/libvirtd --version' \ 'qemu-system-x86_64 --version' 'vagrant --version' do echo "--- Command: ${c} ---" eval "${c}" echo done if which apt-show-versions >/dev/null then echo '--- APT package versions ---' apt-show-versions qemu:amd64 linux-image-amd64:amd64 vagrant \ libvirt0:amd64 fi ) | bzip2 > system-info.txt.bz2 Please have a look at the generated file with bzless system-info.txt.bz2 to make sure it doesn't contain any sensitive information you do not want to leak in case you send this file to us or make it public! Next, please follow the instructions below that match your situation! ## If the build failed. Please open a ticket on our bug tracker [5] with "Category" set to "Build system" and `system-info.txt.bz2` attached (note that this makes this file public). ## If the build succeeded ... Please compute the SHA-512 checksum of the resulting ISO image: sha512sum tails-amd64-3.2~alpha1.iso and compare it to: 1c928336264fc44821562f2fffbda4da97dcdc38072fce58f55b749fde04ac60055273cfc021b6c57120c5d276980859ffa3a5b0bd0f9c98851f34b682a09b02 tails-amd64-3.2~alpha1.iso Bonus points if you verify the signed (with: [8]) message containing the checksum below (note that manually inserted line-wraps marked with "`\`"). If you run Tails, the verification is very easy! :) [9] - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 $ sha512sum tails-amd64-3.2~alpha1.iso 1c928336264fc44821562f2fffbda4da97dcdc38072fce58f55b749f \ de04ac60055273cfc021b6c57120c5d276980859ffa3a5b0bd0f9c98 \ 851f34b682a09b02 tails-amd64-3.2~alpha1.iso - -----BEGIN PGP SIGNATURE----- iQJDBAEBCgAtFiEEuiwiL0SsAO2YmTiTmP7GvHUqPbYFAlmxqwAPHHRhaWxzQGJv dW0ub3JnAAoJEJj+xrx1Kj22RgAP/0auINj6Y5svR7DfeRF8HxPdnd2Rw/8VIiaM isN3eQoAmNGUtEe50b9VXY+UidCdWtApbZbyZPKFz9ITJOxp0XeSGS8K2+Y0PZIx NSIEYCx2LEWlzY96ivH2B4pboeq2TIzj/VkPLISYGc80CYRT32OzMRkDDcQn+3+Y 2dkGVf1HPvreZ7c7cUfozay4TNPhKrn2p5IZp1jHgpiq8aAYIv5jcubR//lm1W3S Ol/IpTQrxzCShJHzsCh1l6/7zLSx5Dv8ITTEIHTj2OTCsZdAcFnznB4byaHVfVQ0 jSogb+b2J6skNhlsHtX2Jo9xK6Ni9NKsCzYYQ2KgWufC93Cvpmh5J164CqkI/DEd ixe/KbFURP9sTzEL38ExS2DVbMvFvYTmmBmWzvU3USMo0nWfaErye2RIs4yB2pM6 wbsgy1g93tQ49YUU0eKFcoUQLnQpKJmZVsLacdkGpLTn7pL9uHR3AcUnRT27CSzb anzpyLVTllyApU+Suu3f5rJibx9ysmLu8gHp5/Osd54qzSBR9JVrhMTkgJmZnit4 67wuSWJDQgvhMKxRz+zB/z4biORIfyblviR4rv1ZbAfX/ChP25CWUxG9Tgk1Esp0 LMzroJyQNfmy++6GrGuHJ3miRsKwO66ot84GSc5/pN1cJHKYiNa4HQhfb+VZBXbk HoXLV3eR =Hhyr - -----END PGP SIGNATURE----- ### ... and the checksums match (i.e. reproduction succeeded). Congrats for successfully reproducing Tails 3.2~alpha1! Please send an email to tails-dev at boum.org (public) or tails at boum.org (private) with the subject "Reproduction of Tails 3.2~alpha1 successful" and attach `system-info.txt.bz2` to it. ### ... and the checksums differ (i.e. reproduction failed). Now you are in a great position to help Tails improve its reproducibility! Please install `diffoscope` [7] version 83 or higher. If you run Debian Stretch, that is: echo 'deb http://ftp.debian.org/debian stretch-backports main' \ | sudo tee /etc/apt/sources.list.d/stretch-backports.list && \ sudo apt update && \ sudo apt -o APT::Install-Suggests="true" \ -o APT::Install-Recommends="true" \ install diffoscope -t stretch-backports Then download the official Tails 3.2~alpha1 ISO image [6] and compare it to yours: diffoscope \ --text diffoscope.txt \ --html diffoscope.html \ --max-report-size 262144000 \ --max-diff-block-lines 10000 \ --max-diff-input-lines 10000000 \ path/to/official/tails-amd64-3.2~alpha1.iso \ path/to/your/tails-amd64-3.2~alpha1.iso && \ bzip2 diffoscope.* Please send an email to tails-dev at boum.org (public) or tails at boum.org (private) with the subject "Reproduction of Tails 3.2~alpha1 failed" and attach `system-info.txt.bz2` to it. We also want you attach one (the smallest!) of `diffoscope.txt.bz2` and `diffoscope.html.bz2` to the email, but if they are "big" (say >100 KiB) then please don't bomb our mail inboxes! Instead upload the file to some web-based file-sharing service (we recommend RiseUp [10]) and include the link(s) in the email. Thank you very much for your interest and help! Cheers! The Tails project [1] https://mailman.boum.org/pipermail/tails-dev/2017-August/011591.html [2] https://labs.riseup.net/code/issues/13624 https://mailman.boum.org/pipermail/tails-dev/2017-March/011297.html [3] https://tails.boum.org/support/#talk [4] https://tails.boum.org/contribute/build [5] https://labs.riseup.net/code/projects/tails/issues/new [6] http://dl.amnesia.boum.org/tails/alpha/tails-amd64-3.2~alpha1/ https://mirrors.wikimedia.org/tails/alpha/tails-amd64-3.2~alpha1/ https://mirrors.kernel.org/tails/alpha/tails-amd64-3.2~alpha1/ [7] https://diffoscope.org/ [8] https://tails.boum.org/tails-signing.key [9] https://tails.boum.org/doc/encryption_and_privacy/gpgapplet/decrypt_verify/ [10] https://share.riseup.net/ -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEEUrafEKOweFrQWvtHHYTM8BDMW8cFAlmxuZIACgkQHYTM8BDM W8fBag/+PlnYIFIfxf4KbPh97Tm9hrNlC6bJp5uTC+6WebBamVsEDekQXnXRzEtF wN4btdFG7MJuLHocSqeiV7gX33A07+KaugqCjQ4NJcVkZ6L9HPK6a1bjn9909EWw l/Cfn0NxaSkfGLhOsk2wFOm2BHU890But+j3bOPOU61JNMVUpwiHUbN2DS1xDK2X ZKE0dlOP3O4TC7kee7rRy6PFUVQx0eQkVW+1qrcusEeHEkc/Z6YzuLmNBdcHJ96m /OfkEi4ygY6l9j0B8z4O/vqPkyeU5VWQWwhhnETvJiSDqs5WNLDuttHOsumP0r29 sluAmicjNoM48mWJHwiyLYnEt5SfFHXOqHXPP1k5YzTOMLRfv/F2eH4Zoq/eI8TM sJy2MO+MgShH8SAOe1vJMBlV9Jqs6t85eToQt+39RFCCn4geyEYlynrk2Ka2hE3n ycn2Qa79nbNK8NJve+1rPZTiJq3lgYyXTYyb8chefKyWm1IsAdY8grS0UIYP44Po KAApudKD75DuCf6qczkOChVeAOcABu63RmAJLnJTYnEwGf7JLJ+KHrCdq0FQQS8s /PulDSSDZo9bhLAHx9tO2T6p2snJfZSf9/dmvM5H+kOlMwzY8GciCgN6wlluwlnU 5WMfAMYT5mhuKIH/WIU5BXlKuUj1MuOi0c64q2MQM2GByJ6SOa8= =6m+4 -----END PGP SIGNATURE-----

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[release] [protocol] Onionoo 4.1-1.4.1
by iwakeh 31 Aug '17

31 Aug '17

Hi there! Onionoo's protocol was extended and has a minor version jump to 4.1, therefore a new release is available: https://dist.torproject.org/onionoo/4.1-1.4.1/ Protocol changes (also summarized in [0]): * removal of (unused) beta fields in bridge client objects * addition of a new search filter parameter by Tor version, see [1] and [2] for example calls. There were also some internal improvements, which can be found in the changelog [3a]. You might have noticed an increment in the middle and minor application version. This is due to a fix for the new filter, which was discovered after creating the 4.1-1.4.0 release, but could be applied before announcing 4.1-1.4.0 (cf.[3b]). Please direct comments and questions to the metrics-team mailing list [4]. Cheers, iwakeh [0] https://metrics.torproject.org/onionoo.html#versions [1] https://onionoo.torproject.org/details?search=version:0.2.4&limit=10 [2] https://onionoo.torproject.org/details?search=version:0.3&limit=10 [3a] https://gitweb.torproject.org/onionoo.git/tree/CHANGELOG.md?h=onionoo-4.1-1… [3b] https://gitweb.torproject.org/onionoo.git/tree/CHANGELOG.md?h=onionoo-4.1-1… [4] https://lists.torproject.org/cgi-bin/mailman/listinfo/metrics-team

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Meeting on IRC to discuss prop280 privcount stuff (Sep 12, 8pm EDT)
by Nick Mathewson 28 Aug '17

28 Aug '17

Hello! On #tor-dev at 8pm EDT on Tuesday Sep 12 (== 00:00 Sep 13 in UTC, I think), we'll have an IRC meeting to talk about proposal 280, and integrating privcount into Tor. If you're interested, please feel free to drop by! The current draft of the proposal is at https://gitweb.torproject.org/torspec.git/tree/proposals/280-privcount-in-t… best wisehes, -- Nick

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Proposal 281: downloading microdescriptors in bulk
by Nick Mathewson 28 Aug '17

28 Aug '17

Filename: 281-bulk-md-download.txt Title: Downloading microdescriptors in bulk Author: Nick Mathewson Created: 11-Aug-2017 Status: Draft 1. Introduction This proposal describes a ways to download more microdescriptors at a time, using fewer bytes. Right now, to download N microdescriptors, the client must send about 44*N bytes in its HTTP request. Because clients can request microdescriptors in any combination, the directory caches cannot pre-compress responses to these requests, and need to use less space-efficient on-the-fly compression algorithms. Under this proposal, clients simply say "Send me the microdescriptors I need", given what I know. 2. Combined microdescriptor downloads 2.1. By diff If a client has a consensus with base64 sha3-256 digest X, and it previously had a consensus with base64 sha3-256 digests Y then it may request all the microdescriptors listed in X but not Y, by asking for the resource: /tor/micro/diff/X/Y Clients SHOULD only ask for this resource compressed. Caches MUST NOT answer this request unless they recognize the consensus with digest X, and digest Y. digest Y. If answering, caches MUST reply with all of the microdescriptors that the cache holds that were listed by consensus X, and MUST omit all the microdescriptors that were omitted listed in consensus Y. 2.2. By consensus: If a client has fewer than NMNM% of the microdescriptors listed in a consensus X, it should fetch the resource /tor/micro/full/X Clients SHOULD only ask for this resource compressed. Caches MUST NOT answer this request unless they recognize the consensus with digest X. They should send all the microdescriptors they have that are listed in that consensus. 2.3. When to make these requests Clients should decide to use this format in preference to the old download-by-digest format if the consensus X lists their preferred directory cache as using a new DirCache subprotocol version. (See 5 below.) 3. Performance analysis This is a back-of-the-envelope analysis using a month's worth of consensus documents, and a randomly chosen sample of microdescriptors. On average, about 0.5% of the microdescriptors change between any two consensuses. Call it 50. That means 50*43 bytes == 2150 bytes to request the microdescriptors. It means ~24530 bytes of microdescriptors downloaded, compressed to ~13687 bytes by zstd. With this proposal, we're down to 86 bytes for the request, and we can precompute the compressed output, making it save to use lzma2, getting a compressed result more like 13362. It appears that this change would save about 15% for incremental microdescriptor downloads, most of that coming from the reduction in request size. For complete downloads, a complete set of microdescriptors is about 7700 microdesciptors long. That makes the total number of bytes for the requests 7700*43 == 331100 bytes. The response, if compressed with lzma instead of zstd, would fall from 1659682 to 1587804 bytes, for a total savings of 20%. 5. Compatibility Caches supporting this download protocol need to advertise support of a new DirCache subprotocol version.

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Some Tor Devs could get higher pay as PR than as programmers
by Ryan Carboni 24 Aug '17

24 Aug '17

Whenever I read something, with an open mind, but say, in a sandboxed environment (don't run your memes on root), I get impressed by arguments which convince me of things which are not true. Take for instance the following article: https://blog.torproject.org/blog/tor-security-advisory-relay-early-traffic-… It is a self-contradictory argument, we detected these bad relays when they arrived, allowed them for 6 months. Now, what was the available prophylactic measures at the time? Alleged family greylisting wasn't available at the time, but certainly an attempt could be made to contact (presumably) a few owners of the tor relays. Although it turned out to be only one owner. I mean, people depend their lives on Tor. Can all discretionary decisions of this type be made public? Now there's also the Tor's unlike racists we value free speech. I cannot explain it, but if one replaced racists with Islamists, somehow the argument is weaker. I can't fully explain it, even though I've heard more about beheadings and defenestrations as opposed to... whatever racists do nowadays (shitpost?). It truly is a clever argument that strengthens and preserves Tor's brand identity among target demographic groups. How did Freud invent psychoanalysis? What are you doing during the idle cycles of your brain? One does not need a fancy degree to be an amateur at anything, or do you folks not call yourselves hackers?

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Draft patchset for PT2.0 support (ticket #21816)
by Robin Tarsiger 24 Aug '17

24 Aug '17

Good day, tor-dev; As some of you know, I've been working on a patchset for Tor to allow it to participate in Pluggable Transports 2.0 configuration, primarily the new JSON Parameter Block SOCKS method (at least that's what I've been calling it in the absence of a more official name), almost but not quite as described in section 3.3.4 of PT2 draft 2 [1]---i.e., basically #21816 [2]. [1] https://www.pluggabletransports.info/assets/PTSpecV2Draft2.pdf [2] https://trac.torproject.org/projects/tor/ticket/21816 I'm attaching a draft patchset which adds this functionality, with the intent of getting feedback and making remaining cleanups or other modifications necessary to get it merged into Tor. I have successfully completed circuits through an obfs4 bridge using both obfs4proxy (PT1) and a version of shapeshifter-dispatcher (PT2) using a patched Tor. I've tried to follow the local style, but the preferred implementation strategies aren't always clear, and of course I'd appreciate any reports of other problems. A forked Git repository is also available on Bitbucket [5][6], which will be updated as I make remaining changes. [5] https://bitbucket.org/DasyatidPrime/tor-rtt2017-21816.git (Git) [6] https://bitbucket.org/DasyatidPrime/tor-rtt2017-21816/src (Web) More implementation details are below if you're interested in this; thanks for your attention. I'll try to be around on IRC more during the week, so feel free to ping me there as well. -RTT ... Details: Not visible above, related to the target functionality: - I'm assuming the SOCKS method includes a response with an analogous structure to RFC 1929; PT2 draft 2 doesn't specify one. I've cleared this with blanu, and that's intended for the next draft of the PT2 specification. - Similarly, the length prefix is in fact big-endian; the example in PT2 draft 2 is wrong, though the text is correct. - We're looking into getting an IANA assignment for the method number. Technically this probably meets the requirements for the private use block, but I feel like interop might be easier later on, and it could simplify code paths in places to have a registered number (mainly if it's possible to decouple the method negotiation from the configuration-version plumbing). I believe this is still in limbo. - For the PT2 side, I've been testing against my branch of shapeshifter-dispatcher [3] compiled with my branch of shapeshifter-ipc [4] since there were some breaking changes to Shapeshifter upstream which were otherwise preventing it from interoperating with Tor. I'm planning to help merge fixes into Shapeshifter upstream as I can; it's my current understanding that there aren't any other PT2 managed transport implementations to test against. [3] https://github.com/OperatorFoundation/shapeshifter-dispatcher/tree/rtt2017 [4] https://github.com/OperatorFoundation/shapeshifter-ipc/tree/rtt2017 Issues on my radar currently (comments appreciated): - We probably want unit tests for the (limited) JSON encoding functions, and for the factored-out RFC 1929 encoding functions. Anything else that looks feasibly testable here? - It's not clear to me whether negotiating a PT2 configuration version still allows PT1-style RFC 1929 parameter encoding so that managed transports can support the new configuration version and the new SOCKS method separately. I've assumed it might be possible, so far, but that's not being tested against anything. - I currently restrict parameters to ASCII to avoid either writing a JSON encoder that can spit out invalid JSON or writing a JSON encoder that has to validate incoming UTF-8. The impression I've gotten is that this is probably okay, but if there are counter- examples, I can put in UTF-8 passthrough. - The commit sequence isn't the cleanest. How high a priority is it to reorder/combine patch hunks to make a cleaner one? - We still need a 'changes' file. (What would be an appropriate heading for this? Is this a minor feature, for instance?) A few other questions: - Is there an effective way of doing automated testing of the SOCKS state machine currently in Tor? I didn't see anything obvious in the test directory. This seems like the most fragile part, especially since both the original and modified versions are not very explicit in their state machine nature and are split between multiple files. - Can there ever be more than one managed_proxy_t to a transport name? More generally, is there a relational diagram of the main Tor data structures somewhere? A lot of the way the plumbing for state and configuration information is set up feels kind of fragile.

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Tor and IP2Location LITE
by KL Liew 24 Aug '17

24 Aug '17

All, My name is Kim, the founder of IP2Location, a geolocation service provider since 2002. It looks like Tor is looking to review other providers for GeoIP service while I was reading one of a meeting minute for a meeting back in March 2017. https://trac.torproject.org/projects/tor/wiki/org/meetings/2017Amsterdam/No… We are very interested in contributing to Tor and work on this matter. Tor can host and integrate IP2Location LITE (http://lite.ip2location.com) into their application. IP2Location has programming libraries in most languages. We can also work with developers if there is any technical issues. In term of accuracy, you can find the latest research paper published by TUM. IP2Location has good accuracy as reported in Table V. Title : HLOC: Hints-Based Geolocation Leveraging Multiple Measurement Frameworks Authors : Quirin Scheitle, Oliver Gasser, Patrick Sattler, Georg Carle from Technical University of Munich (TUM) PDF Access : https://arxiv.org/pdf/1706.09331.pdf Let me know if there is any questions. - Kim

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Re: [tor-dev] tor-dev Digest, Vol 79, Issue 4
by John kongtcheu 21 Aug '17

21 Aug '17

Hello Tor developers, I am interested in becoming an open source contributor for Tor, but I don't know where to start some guidance would be appreciated. Thank you, On Sat, Aug 12, 2017 at 8:00 AM, <tor-dev-request(a)lists.torproject.org> wrote: > Send tor-dev mailing list submissions to > tor-dev(a)lists.torproject.org > > To subscribe or unsubscribe via the World Wide Web, visit > https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-dev > or, via email, send a message with subject or body 'help' to > tor-dev-request(a)lists.torproject.org > > You can reach the person managing the list at > tor-dev-owner(a)lists.torproject.org > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of tor-dev digest..." > > > Today's Topics: > > 1. Proposal 281: downloading microdescriptors in bulk > (Nick Mathewson) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Fri, 11 Aug 2017 13:36:00 -0400 > From: Nick Mathewson <nickm(a)torproject.org> > To: tor-dev(a)lists.torproject.org > Subject: [tor-dev] Proposal 281: downloading microdescriptors in bulk > Message-ID: > <CAKDKvux=eJBh_JsEeiqnhbEbcgRVeMRrbm2G7itZ8kX > y4+M26A(a)mail.gmail.com> > Content-Type: text/plain; charset="UTF-8" > > Filename: 281-bulk-md-download.txt > Title: Downloading microdescriptors in bulk > Author: Nick Mathewson > Created: 11-Aug-2017 > Status: Draft > > 1. Introduction > > This proposal describes a ways to download more microdescriptors > at a time, using fewer bytes. > > Right now, to download N microdescriptors, the client must send > about 44*N bytes in its HTTP request. Because clients can request > microdescriptors in any combination, the directory caches cannot > pre-compress responses to these requests, and need to use less > space-efficient on-the-fly compression algorithms. > > Under this proposal, clients simply say "Send me the > microdescriptors I need", given what I know. > > 2. Combined microdescriptor downloads > > 2.1. By diff > > If a client has a consensus with base64 sha3-256 digest X, and it > previously had a consensus with base64 sha3-256 digests Y then > it may request all the microdescriptors listed in X but not Y, > by asking for the resource: > /tor/micro/diff/X/Y > > Clients SHOULD only ask for this resource compressed. > > Caches MUST NOT answer this request unless they recognize the > consensus with digest X, and digest Y. > digest Y. If answering, caches MUST reply with all of the > microdescriptors that the cache holds that were listed by > consensus X, and MUST omit all the microdescriptors that were > omitted listed in consensus Y. > > 2.2. By consensus: > > If a client has fewer than NMNM% of the microdescriptors listed in a > consensus X, it should fetch the resource > /tor/micro/full/X > > Clients SHOULD only ask for this resource compressed. > > Caches MUST NOT answer this request unless they recognize the > consensus with digest X. They should send all the microdescriptors > they have that are listed in that consensus. > > 2.3. When to make these requests > > Clients should decide to use this format in preference to the > old download-by-digest format if the consensus X lists their > preferred directory cache as using a new DirCache subprotocol > version. (See 5 below.) > > 3. Performance analysis > > This is a back-of-the-envelope analysis using a month's worth of > consensus documents, and a randomly chosen sample of > microdescriptors. > > > On average, about 0.5% of the microdescriptors change between any > two consensuses. Call it 50. That means 50*43 bytes == 2150 > bytes to request the microdescriptors. It means ~24530 bytes of > microdescriptors downloaded, compressed to ~13687 bytes by zstd. > > With this proposal, we're down to 86 bytes for the request, and we > can precompute the compressed output, making it save to use lzma2, > getting a compressed result more like 13362. > > It appears that this change would save about 15% for incremental > microdescriptor downloads, most of that coming from the reduction > in request size. > > For complete downloads, a complete set of microdescriptors is about > 7700 microdesciptors long. That makes the total number of bytes > for the requests 7700*43 == 331100 bytes. The response, if > compressed with lzma instead of zstd, would fall from 1659682 to > 1587804 bytes, for a total savings of 20%. > > > 5. Compatibility > > Caches supporting this download protocol need to advertise > support of a new DirCache subprotocol version. > > > ------------------------------ > > Subject: Digest Footer > > _______________________________________________ > tor-dev mailing list > tor-dev(a)lists.torproject.org > https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-dev > > > ------------------------------ > > End of tor-dev Digest, Vol 79, Issue 4 > ************************************** >

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