May 2019 - tor-commits - lists.torproject.org

[translation/support-portal] Update translations for support-portal
by translation＠torproject.org 16 May '19

16 May '19

commit d094b077be444c87012b200e0181295f2f539e84 Author: Translation commit bot <translation(a)torproject.org> Date: Thu May 16 15:20:55 2019 +0000 Update translations for support-portal --- contents+fr.po | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) diff --git a/contents+fr.po b/contents+fr.po index 25e84da84..1e393f569 100644 --- a/contents+fr.po +++ b/contents+fr.po @@ -5461,8 +5461,8 @@ msgid "" "](#cryptographic-signature) to proof the identity of the creator of a " "message or other files." msgstr "" -"De plus, la clé privée peut être utilisée pour créer " -"une[signature](#signature cryptographique) pour prouver l’identité du " +"De plus, la clé privée peut être utilisée pour créer une " +"[signature](#signature cryptographique) afin de prouver l’identité du " "créateur d’un message ou d’autres fichiers." #: https//support.torproject.org/misc/glossary/ @@ -5492,10 +5492,9 @@ msgid "" "that forwards [traffic](#traffic) on behalf of [clients](#client), and that " "registers itself with the [directory authorities](#directory-authority)." msgstr "" -"Un noeud coté publiquement dans le [réseau Tor](#tor-/-tor-tor-network" -"/-core-tor) qui achemine le [trafic](#trafic) au nom des [clients](#client)," -" et qui s’enregistre auprès des [autorités de répertoire](#directory-" -"authority)." +"Un nœud, publié publiquement, dans le [réseau Tor](#tor-/-tor-tor-network" +"/-core-tor) qui achemine le [trafic](#trafic) au nom de [clients](#client) " +"et qui s’inscrit auprès des [autorités de répertoire](#directory-authority)." #: https//support.torproject.org/misc/glossary/ #: (content/misc/glossary/contents+en.lrquestion.description) @@ -5532,8 +5531,8 @@ msgid "" "Scramblesuit is similar to obfs4 but has a different set of " "[bridges](#bridge)." msgstr "" -"Scramblesuit est similaire à obfs4 mais a un ensemble différent de " -"[ponts](#bridge)." +"Scramblesuit s’apparente à obfs4, mais avec un jeu de [ponts](#bridge) " +"différent." #: https//support.torproject.org/misc/glossary/ #: (content/misc/glossary/contents+en.lrquestion.description)

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[translation/tbmanual-contentspot_completed] Update translations for tbmanual-contentspot_completed
by translation＠torproject.org 16 May '19

16 May '19

commit 20224ffe16e9db95ea82749b9fc3f5e0e50f9fa0 Author: Translation commit bot <translation(a)torproject.org> Date: Thu May 16 15:18:03 2019 +0000 Update translations for tbmanual-contentspot_completed --- contents+fr.po | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/contents+fr.po b/contents+fr.po index fb700c870..5a576075a 100644 --- a/contents+fr.po +++ b/contents+fr.po @@ -1568,9 +1568,9 @@ msgid "" "Increasing the level of the Security Slider will disable or partially " "disable certain browser features to protect against possible attacks." msgstr "" -"En augmentant le niveau du curseur de sécurité, vous désactiverez " -"complètement ou partiellement certaines fonctions du navigateur afin de vous" -" protéger contre les attaques potentielles." +"Augmenter le niveau du curseur de sécurité désactivera complètement ou " +"partiellement certaines fonctions du navigateur afin d’offrir une protection" +" contre les attaques possibles." #: https//tb-manual.torproject.org/en-US/security-slider/ #: (content/security-slider/contents+en-US.lrtopic.body)

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[translation/tbmanual-contentspot] Update translations for tbmanual-contentspot
by translation＠torproject.org 16 May '19

16 May '19

commit 0eb626db9d191241a6e6689a67d6bca72c95983f Author: Translation commit bot <translation(a)torproject.org> Date: Thu May 16 15:17:56 2019 +0000 Update translations for tbmanual-contentspot --- contents+fr.po | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/contents+fr.po b/contents+fr.po index fb700c870..5a576075a 100644 --- a/contents+fr.po +++ b/contents+fr.po @@ -1568,9 +1568,9 @@ msgid "" "Increasing the level of the Security Slider will disable or partially " "disable certain browser features to protect against possible attacks." msgstr "" -"En augmentant le niveau du curseur de sécurité, vous désactiverez " -"complètement ou partiellement certaines fonctions du navigateur afin de vous" -" protéger contre les attaques potentielles." +"Augmenter le niveau du curseur de sécurité désactivera complètement ou " +"partiellement certaines fonctions du navigateur afin d’offrir une protection" +" contre les attaques possibles." #: https//tb-manual.torproject.org/en-US/security-slider/ #: (content/security-slider/contents+en-US.lrtopic.body)

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[translation/exoneratorproperties_completed] Update translations for exoneratorproperties_completed
by translation＠torproject.org 16 May '19

16 May '19

commit 3804e886419dfb47d3b5c6e2ece9a38610e5cd01 Author: Translation commit bot <translation(a)torproject.org> Date: Thu May 16 15:15:50 2019 +0000 Update translations for exoneratorproperties_completed --- pt_PT/exonerator.properties | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/pt_PT/exonerator.properties b/pt_PT/exonerator.properties index 5236fad54..e8ee52a4c 100644 --- a/pt_PT/exonerator.properties +++ b/pt_PT/exonerator.properties @@ -43,10 +43,9 @@ technicaldetails.exit.yes=Sim technicaldetails.exit.no=Não permanentlink.heading=Link permanente footer.abouttor.heading=Sobre o Tor -footer.abouttor.body.text=O Tor é um projeto de software internacional para tornar anónimo o tráfego da Internet por %s. Portanto, se vir tráfego de uma retransmissão do Tor, este tráfego geralmente tem a sua origem em alguém que está a utilizar o Tor, em vez de um operador de retransmissão. O Projeto Tor e os operadores de retransmissão do Tor não têm registos do tráfego que passa pela rede, e por isso, não podem fornecer qualquer informação sobre a sua origem. Certifique-se que %s, e não hesite em %s para obter mais informação. -footer.abouttor.body.link1=encriptar pacotes e enviá-los através de uma série de etapas antes de estes atingirem o seu destino -footer.abouttor.body.link2=saber mais sobre o Tor -footer.abouttor.body.link3=contactar The Tor Project, Inc. +footer.abouttor.body.text=O Tor é um projeto de software internacional para tornar anónimo o tráfego da Internet através da encriptação de pacotes de dados e o envio dos mesmos por uma série de saltos antes de chegarem ao seu destino.  Logo, se vir tráfego de uma Tor relay, este tráfego geralmente tem a sua origem em alguém que está a utilizar o Tor, em vez de um operador do relay.  O Projeto Tor e os operadores de retransmissão do Tor não têm registos do tráfego que passa pela rede, e por isso, não podem fornecer qualquer informação sobre a sua origem.  Certifique-se que %s, e não hesite em %s para obter mais informação. +footer.abouttor.body.link1=saber mais sobre o Tor +footer.abouttor.body.link2=contactar The Tor Project, Inc. footer.aboutexonerator.heading=Sobre o ExoneraTor footer.aboutexonerator.body=O serviço ExoneraTor mantém uma base de dados de endereços de IP que têm sido parte da rede Tor. Este responde à pergunta sobre se houve uma retransmissão Tor em execução num determinado endereço de IP numa determinada data. ExoneraTor poderá armazenar mais do que um endereço de IP por retransmissão, se as retransmissões utilizarem um endereço de IP diferente para sair da Internet do que o registado na rede Tor, e este armazena a passagem permitida de uma retransmissão do tráfego do Tor para a Internet aberta no momento. footer.language.name=Inglês

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[translation/exoneratorproperties] Update translations for exoneratorproperties
by translation＠torproject.org 16 May '19

16 May '19

commit b26cee5f3b433f29a477823951387a9157d2ca99 Author: Translation commit bot <translation(a)torproject.org> Date: Thu May 16 15:15:45 2019 +0000 Update translations for exoneratorproperties --- pt_PT/exonerator.properties | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/pt_PT/exonerator.properties b/pt_PT/exonerator.properties index d31b60777..e8ee52a4c 100644 --- a/pt_PT/exonerator.properties +++ b/pt_PT/exonerator.properties @@ -43,7 +43,7 @@ technicaldetails.exit.yes=Sim technicaldetails.exit.no=Não permanentlink.heading=Link permanente footer.abouttor.heading=Sobre o Tor -footer.abouttor.body.text=Tor is an international software project to anonymize Internet traffic by encrypting packets and sending them through a series of hops before they reach their destination.  Therefore, if you see traffic from a Tor relay, this traffic usually originates from someone using Tor, rather than from the relay operator.  The Tor Project and Tor relay operators have no records of the traffic that passes over the network and therefore cannot provide any information about its origin.  Be sure to %s, and don't hesitate to %s for more information. +footer.abouttor.body.text=O Tor é um projeto de software internacional para tornar anónimo o tráfego da Internet através da encriptação de pacotes de dados e o envio dos mesmos por uma série de saltos antes de chegarem ao seu destino.  Logo, se vir tráfego de uma Tor relay, este tráfego geralmente tem a sua origem em alguém que está a utilizar o Tor, em vez de um operador do relay.  O Projeto Tor e os operadores de retransmissão do Tor não têm registos do tráfego que passa pela rede, e por isso, não podem fornecer qualquer informação sobre a sua origem.  Certifique-se que %s, e não hesite em %s para obter mais informação. footer.abouttor.body.link1=saber mais sobre o Tor footer.abouttor.body.link2=contactar The Tor Project, Inc. footer.aboutexonerator.heading=Sobre o ExoneraTor

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[translation/support-portal_completed] Update translations for support-portal_completed
by translation＠torproject.org 16 May '19

16 May '19

commit 301d777afefbf84eab08cf2ce27a069a04eb42f2 Author: Translation commit bot <translation(a)torproject.org> Date: Thu May 16 14:50:56 2019 +0000 Update translations for support-portal_completed --- contents+pt-PT.po | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/contents+pt-PT.po b/contents+pt-PT.po index af010dee2..d5ccb77f4 100644 --- a/contents+pt-PT.po +++ b/contents+pt-PT.po @@ -4670,6 +4670,9 @@ msgid "" "[traffic](#traffic) moving between [relays](#relay) in a " "[circuit](#circuit)." msgstr "" +"Em linguagem de [Tor](#tor-/-tor-network/-core-tor), um \"salto\" refere-se " +"ao [tráfico](#traffic) que se move entre [relays](#relay) dentro de um " +"[circuito](#circuit)." #: https//support.torproject.org/misc/glossary/ #: (content/misc/glossary/contents+en.lrquestion.description) @@ -4684,6 +4687,10 @@ msgid "" "only web pages, it is now relied upon to deliver many forms of data and " "communication." msgstr "" +"O [Protocolo de Transferência de Hipertexto (HTTP)](#http) é um canal " +"utilizado para enviar ficheiro e dados entre dispositivos numa rede. " +"Originalmente utilizado para transferir apenas páginas web, é agora confiado" +" para entregar muitas formas de dados e comunicação. " #: https//support.torproject.org/misc/glossary/ #: (content/misc/glossary/contents+en.lrquestion.description) @@ -4704,7 +4711,7 @@ msgstr "" #: https//support.torproject.org/misc/glossary/ #: (content/misc/glossary/contents+en.lrquestion.description) msgid "### HTTPS Everywhere" -msgstr "" +msgstr "### HTTPS Everywhere" #: https//support.torproject.org/misc/glossary/ #: (content/misc/glossary/contents+en.lrquestion.description) @@ -4768,6 +4775,8 @@ msgid "" "The IP address is the location address of the device, similar to the " "addresses of physical locations." msgstr "" +"O endereço IP é o endereço de localização do dispositivo, semelhante ao " +"endereço de localizações físicas." #: https//support.torproject.org/misc/glossary/ #: (content/misc/glossary/contents+en.lrquestion.description)

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[translation/support-portal] Update translations for support-portal
by translation＠torproject.org 16 May '19

16 May '19

commit f7d9fa400734fa4cf912bda700481863765b2b06 Author: Translation commit bot <translation(a)torproject.org> Date: Thu May 16 14:50:49 2019 +0000 Update translations for support-portal --- contents+pt-PT.po | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/contents+pt-PT.po b/contents+pt-PT.po index af010dee2..d5ccb77f4 100644 --- a/contents+pt-PT.po +++ b/contents+pt-PT.po @@ -4670,6 +4670,9 @@ msgid "" "[traffic](#traffic) moving between [relays](#relay) in a " "[circuit](#circuit)." msgstr "" +"Em linguagem de [Tor](#tor-/-tor-network/-core-tor), um \"salto\" refere-se " +"ao [tráfico](#traffic) que se move entre [relays](#relay) dentro de um " +"[circuito](#circuit)." #: https//support.torproject.org/misc/glossary/ #: (content/misc/glossary/contents+en.lrquestion.description) @@ -4684,6 +4687,10 @@ msgid "" "only web pages, it is now relied upon to deliver many forms of data and " "communication." msgstr "" +"O [Protocolo de Transferência de Hipertexto (HTTP)](#http) é um canal " +"utilizado para enviar ficheiro e dados entre dispositivos numa rede. " +"Originalmente utilizado para transferir apenas páginas web, é agora confiado" +" para entregar muitas formas de dados e comunicação. " #: https//support.torproject.org/misc/glossary/ #: (content/misc/glossary/contents+en.lrquestion.description) @@ -4704,7 +4711,7 @@ msgstr "" #: https//support.torproject.org/misc/glossary/ #: (content/misc/glossary/contents+en.lrquestion.description) msgid "### HTTPS Everywhere" -msgstr "" +msgstr "### HTTPS Everywhere" #: https//support.torproject.org/misc/glossary/ #: (content/misc/glossary/contents+en.lrquestion.description) @@ -4768,6 +4775,8 @@ msgid "" "The IP address is the location address of the device, similar to the " "addresses of physical locations." msgstr "" +"O endereço IP é o endereço de localização do dispositivo, semelhante ao " +"endereço de localizações físicas." #: https//support.torproject.org/misc/glossary/ #: (content/misc/glossary/contents+en.lrquestion.description)

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[translation/support-portal_completed] Update translations for support-portal_completed
by translation＠torproject.org 16 May '19

16 May '19

commit f7229bdd03a578db30c77b78b0ece94b6ec76605 Author: Translation commit bot <translation(a)torproject.org> Date: Thu May 16 14:21:03 2019 +0000 Update translations for support-portal_completed --- contents+pt-PT.po | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/contents+pt-PT.po b/contents+pt-PT.po index a61ae56f2..af010dee2 100644 --- a/contents+pt-PT.po +++ b/contents+pt-PT.po @@ -639,7 +639,7 @@ msgstr "" #: https//support.torproject.org/tbb/how-to-verify-signature/ #: (content/tbb/how-to-verify-signature/contents+en.lrquestion.description) msgid "### macOS and Linux" -msgstr "" +msgstr "### macOS e Linux" #: https//support.torproject.org/tbb/how-to-verify-signature/ #: (content/tbb/how-to-verify-signature/contents+en.lrquestion.description) @@ -2574,7 +2574,7 @@ msgstr "* Linux" #: https//support.torproject.org/gettor/gettor-4/ #: (content/gettor/gettor-4/contents+en.lrquestion.description) msgid "* macOS (OS X)" -msgstr "" +msgstr "* macOS (OS X)" #: https//support.torproject.org/gettor/gettor-3/ #: (content/gettor/gettor-3/contents+en.lrquestion.description) @@ -3285,6 +3285,8 @@ msgstr "#Endereço noname.example.com" msgid "" "## A handle for your relay, so people don't have to refer to it by key." msgstr "" +"## Um handle para o seu relay, para que não tenha de ser referido pela sua " +"chave." #: https//support.torproject.org/operators/operators-1/ #: (content/operators/operators-1/contents+en.lrquestion.description) @@ -3689,6 +3691,9 @@ msgid "" "https://deb.torproject.org/torproject.org/A3C4F0F979CAA22CDBA8F512EE8CBC9E8…" " | sudo apt-key add -" msgstr "" +"$ curl " +"https://deb.torproject.org/torproject.org/A3C4F0F979CAA22CDBA8F512EE8CBC9E8…" +" | sudo apt-key add -" #: https//support.torproject.org/operators/operators-4/ #: (content/operators/operators-4/contents+en.lrquestion.description)

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[translation/support-portal] Update translations for support-portal
by translation＠torproject.org 16 May '19

16 May '19

commit feb02f77dd12fb809ce4c28358f71e20607738ee Author: Translation commit bot <translation(a)torproject.org> Date: Thu May 16 14:20:56 2019 +0000 Update translations for support-portal --- contents+pt-PT.po | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/contents+pt-PT.po b/contents+pt-PT.po index a61ae56f2..af010dee2 100644 --- a/contents+pt-PT.po +++ b/contents+pt-PT.po @@ -639,7 +639,7 @@ msgstr "" #: https//support.torproject.org/tbb/how-to-verify-signature/ #: (content/tbb/how-to-verify-signature/contents+en.lrquestion.description) msgid "### macOS and Linux" -msgstr "" +msgstr "### macOS e Linux" #: https//support.torproject.org/tbb/how-to-verify-signature/ #: (content/tbb/how-to-verify-signature/contents+en.lrquestion.description) @@ -2574,7 +2574,7 @@ msgstr "* Linux" #: https//support.torproject.org/gettor/gettor-4/ #: (content/gettor/gettor-4/contents+en.lrquestion.description) msgid "* macOS (OS X)" -msgstr "" +msgstr "* macOS (OS X)" #: https//support.torproject.org/gettor/gettor-3/ #: (content/gettor/gettor-3/contents+en.lrquestion.description) @@ -3285,6 +3285,8 @@ msgstr "#Endereço noname.example.com" msgid "" "## A handle for your relay, so people don't have to refer to it by key." msgstr "" +"## Um handle para o seu relay, para que não tenha de ser referido pela sua " +"chave." #: https//support.torproject.org/operators/operators-1/ #: (content/operators/operators-1/contents+en.lrquestion.description) @@ -3689,6 +3691,9 @@ msgid "" "https://deb.torproject.org/torproject.org/A3C4F0F979CAA22CDBA8F512EE8CBC9E8…" " | sudo apt-key add -" msgstr "" +"$ curl " +"https://deb.torproject.org/torproject.org/A3C4F0F979CAA22CDBA8F512EE8CBC9E8…" +" | sudo apt-key add -" #: https//support.torproject.org/operators/operators-4/ #: (content/operators/operators-4/contents+en.lrquestion.description)

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[torspec/master] add 302-padding-machines-for-onion-clients.txt
by nickm＠torproject.org 16 May '19

16 May '19

commit 9503a261020ad906bb07595d8fba25b4542bba8a Author: Nick Mathewson <nickm(a)torproject.org> Date: Thu May 16 09:45:15 2019 -0400 add 302-padding-machines-for-onion-clients.txt --- proposals/000-index.txt | 2 + .../302-padding-machines-for-onion-clients.txt | 299 +++++++++++++++++++++ 2 files changed, 301 insertions(+) diff --git a/proposals/000-index.txt b/proposals/000-index.txt index a504c27..5982230 100644 --- a/proposals/000-index.txt +++ b/proposals/000-index.txt @@ -222,6 +222,7 @@ Proposals by number: 299 Preferring IPv4 or IPv6 based on IP Version Failure Count [OPEN] 300 Walking Onions: Scaling and Saving Bandwidth [DRAFT] 301 Don't include package fingerprints in consensus documents [ACCEPTED] +302 Hiding onion service clients using padding [ACCEPTED] Proposals by status: @@ -262,6 +263,7 @@ Proposals by status: 288 Privacy-Preserving Statistics with Privcount in Tor (Shamir version) 292 Mesh-based vanguards 301 Don't include package fingerprints in consensus documents + 302 Hiding onion service clients using padding META: 000 Index of Tor Proposals 001 The Tor Proposal Process diff --git a/proposals/302-padding-machines-for-onion-clients.txt b/proposals/302-padding-machines-for-onion-clients.txt new file mode 100644 index 0000000..d7f583e --- /dev/null +++ b/proposals/302-padding-machines-for-onion-clients.txt @@ -0,0 +1,299 @@ +Filename: 302-padding-machines-for-onion-clients.txt +Title: Hiding onion service clients using padding +Author: George Kadianakis, Mike Perry +Created: Thursday 16 May 2019 +Status: Accepted +Ticket: #28634 + +0. Overview + + Tor clients use "circuits" to do anonymous communications. There are various + types of circuits. Some of them are for navigating the normal Internet, + others are for fetching Tor directory information, others are for connecting + to onion services, while others are simply for measurements and testing. + + It's currently possible for MITM type of adversaries (like tor-network-level + and local-area-network adversaries) to distinguish Tor circuit types from + each other using a wide array of metadata and distinguishers. + + In this proposal, we study various techniques that can be used to + distinguish client-side onion service circuits and provide WTF-PAD circuit + padding machines (using prop#254) to hide them against certain adversaries. + +1. Motivation + + We are writing this proposal for various reasons: + + 1) We believe that in an ideal setting MITM adversaries should not be able + to distinguish circuit types by inspecting traffic. Tor traffic should + look amorphous to an outside observer to maximize uncertainty and + anonymity properties. + + Client-side onion service circuits are an easy target for this proposal, + because we believe we can improve their privacy with low bandwidth + overhead. + + 2) We want to start experimenting with the WTF-PAD subsystem of Tor, and + this use-case provides us with a good testbed. + + 3) We hope that by actually starting to use the WTF-PAD subsystem of Tor, we + will encourage more researchers to start experimenting with it. + +2. Scope of the proposal [SCOPE] + + Given the above, this proposal sets forth to use the WTF-PAD system to hide + client-side onion service circuits against the classifiers of paper by Kwon + et al. above. + + By client-side onion service circuits we refer to these two types of circuits: + - Client-side introduction circuits: Circuit from client to the introduction point + - Client-side rendezvous circuits: Circuit from client to the rendezvous point + + Service-side onion service circuits are not in scope for this proposal, and + this is because hiding those would require more bandwidth and also more + advanced WTF-PAD features. + + Furthermore, this proposal only aims to cloak the naive distinguishing + features mentioned in the [KNOWN_DISTINGUISHERS] section, and can by no + means guarantee that client-side onion service circuits are totally + indistinguishable by other means. + + The machines specified in this proposal are meant to be lightweight and + created for a specific purpose. This means that they can be easily extended + with additional states to do more advanced hiding. + +3. Known distinguishers against onion service circuits [KNOWN_DISTINGUISHERS] + + Over the past years it's been assumed that motivated adversaries can + distinguish onion-service traffic from normal Tor traffic given their + special characteristics. + + As far as we know, there has been relatively little research-level work done + to this direction. The main article published in this area is the USENIX + paper "Circuit Fingerprinting Attacks: Passive Deanonymization of Tor Hidden + Services" by Kwon et al. [0] + + The above paper deals with onion service circuits in sections 3.2 and 5.1. + It uses the following three "naive" circuit features to distinguish circuits: + 1) Circuit construction sequence + 2) Number of incoming and outgoing cells + 3) Duration of Activity ("DoA") + + All onion service circuits have particularly loud signatures to the above + characteristics, but WTF-PAD (prop#254) gives us tools to effectively + silence those signatures to the point where the paper's classifiers won't + work. + +4. Hiding circuit features using WTF-PAD + + According to section [KNOWN_DISTINGUISHERS] there are three circuit features + we are attempting to hide. Here is how we plan to do this using the WTF-PAD + system: + + 1) Circuit construction sequence + + The USENIX paper uses the directions of the first 10 cells sent in a + circuit to fingerprint them. Client-side onion service circuits have + unique circuit construction sequences and hence they can be fingeprinted + using just the first 10 cells. + + We use WTF-PAD to destroy this feature of onion service circuits by + carefully sending padding cells (relay DROP cells) during circuit + construction and making them look exactly like most general tor circuits + up till the end of the circuit construction sequence. + + 2) Number of incoming and outgoing cells + + The USENIX paper uses the amount of incoming and outgoing cells to + distinguish circuit types. For example, client-side introduction circuits + have the same amount of incoming and outgoing cells, whereas client-side + rendezvous circuits have more incoming than outgoing cells. + + We use WTF-PAD to destroy this feature by changing the number of cells + sent in introduction circuits. We leave rendezvous circuits as is, since + the actual rendezvous traffic flow usually resembles well normal Tor + circuits. + + 3) Duration of Activity ("DoA") + + The USENIX paper uses the period of time during which circuits send and + receive cells to distinguish circuit types. For example, client-side + introduction circuits are really short lived, wheras service-side + introduction circuits are very long lived. OTOH, rendezvous circuits have + the same median lifetime as general Tor circuits which is 10 minutes. + + We use WTF-PAD to destroy this feature of client-side introduction + circuits by setting a special WTF-PAD option, which keeps the circuits + open for 10 minutes completely mimicking the DoA of general Tor circuits. + +4.1. A dive into general circuit construction sequences [CIRCCONSTRUCTION] + + In this section we give an overview of how circuit construction looks like + to a network or guard-level adversary. We use this knowledge to make the + right padding machines that can make intro and rend circuits look like these + general circuits. + + In particular, most general Tor circuits used to surf the web or download + directory information, start with the following 6-cell relay cell sequence (cells + surrounded in [brackets] are outgoing, the others are incoming): + + [EXTEND2] -> EXTENDED2 -> [EXTEND2] -> EXTENDED2 -> [BEGIN] -> CONNECTED + + When this is done, the client has established a 3-hop circuit and also + opened a stream to the other end. Usually after this comes a series of DATA + cell that either fetches pages, establishes an SSL connection or fetches + directory information: + + [DATA] -> [DATA] -> DATA -> DATA + + The above stream of 10 relay cells defines the grand majority of general + circuits that come out of Tor browser during our testing, and it's what we + are gonna use to make introduction and rednezvous circuits blend in. + + Please note that in this section we only investigate relay cells and not + connection-level cells like CREATE/CREATED or AUTHENTICATE/etc. that are + used during the link-layer handshake. The rationale is that connection-level + cells depend on the type of guard used and are not an effective fingerprint + for a network/guard-level adversary. + +5. WTF-PAD machines + + For the purposes of this proposal we will make use of four WTF-PAD machines + as follows: + + - Client-side introduction circuit hiding machine (origin-side) + - Client-side introduction circuit hiding machine (relay-side) + + - Client-side rendezvous circuit hiding machine (origin-side) + - Client-side rendezvous circuit hiding machine (relay-side) + + In the following sections we will analyze these machines. + +5.1. Client-side introduction circuit hiding machines [INTRO_CIRC_HIDING] + + These two machines are meant to hide client-side introduction circuits. The + origin-side machine sits on the client and sends padding towards the + introduction circuit, whereas the relay-side machine sits on the middle-hop + (second hop of the circuit) and sends padding towards the client. The + padding from the origin-side machine terminates at the middle-hop and does + not get forwarded to the actual introduction point. + + Both of these machines only get activated for introduction circuits, and + only after an INTRODUCE1 cell has been sent out. + + This means that before the machine gets activated our cell flow looks like this: + + [EXTEND2] -> EXTENDED2 -> [EXTEND2] -> EXTENDED2 -> [EXTEND2] -> EXTENDED2 -> [INTRODUCE1] + + Comparing the above with section [CIRCCONSTRUCTION], we see that the above + cell sequence matches the one from general circuits up to the first 7 cells. + + However, in normal introduction circuits this is followed by an + INTRODUCE_ACK and then the circuit gets teared down, which does not match + the sequence from [CIRCCONSTRUCTION]. + + Hence when our machine is used, after sending an [INTRODUCE1] cell, we also + send a [PADDING_NEGOTIATE] cell, which gets answered by a PADDING_NEGOTIATED + cell and an INTRODUCE_ACKED cell. This makes us match the [CIRCCONSTRUCTION] + sequence up to the first 10 cells. + + After that, we continue sending padding from the relay-side machine so as to + fake a directory download, or an SSL connection setup. We also want to + continue sending padding so that the connection stays up longer to destroy + the "Duration of Activity" fingerprint. + + To calculate the padding overhead, we see that the origin-side machine just + sends a single [PADDING_NEGOATIATE] cell, wheras the origin-side machine + sends a PADDING_NEGOTIATED cell and between 7 to 10 DROP cells. This means + that the average overhead of this machine is 11 padding cells. + + In terms of WTF-PAD terminology, these machines have three states (START, + OBF, END). They move from the START to OBF state when the first + non-padding cell is received on the circuit, and they stay in the OBF + state until all the padding gets depleted. The OBF state is controlled by + a histogram which specifies the parameters described in the paragraphs + above. After all the padding finishes, it moves to END state. + + We also set a special WTF-PAD flag which keeps the circuit open even after + the introduction is performed. In particular, with this feature the circuit + will stay alive for the same durations as normal web circuits before they + expire (usually 10 minutes). + +5.2. Client-side rendezvous circuit hiding machines + + The rendezvous circuit machines apply on client-side rendezvous circuits and + only after the rendezvous point has been established (REND_ESTABLISHED has + been received). Up to that point, the following cell sequence has been + observed on the circuit: + + [EXTEND2] -> EXTENDED2 -> [EXTEND2] -> EXTENDED2 -> [ESTABLISH_REND] -> REND_ESTABLISHED + + which matches the general circuit construction sequence [CIRCCONSTRUCTION] + up to the first 6 cells. However after that, normal rendezvous circuits + receive a RENDEZVOUS2 cell followed by a [BEGIN] and a CONNECTED, which does + not fit the circuit construction sequence we are trying to imitate. + + Hence our machine gets activated right after REND_ESTABLISHED is received, + and continues by sending a [PADDING_NEGOTIATE] and a [DROP] cell, before + receiving a PADDING_NEGOTIATED and a DROP cell, effectively blending into + the general circuit construction sequence on the first 10 cells. + + After that our machine gets deactivated, and we let the actual rendezvous + circuit shape the traffic flow. Since rendezvous circuits usually immitate + general circuits (their purpose is to surf the web), we can expect that they + will look alike. + + In terms of overhead, this machine is quite light. Both sides send 2 padding + cells, for a total of 4 padding cells. + +6. Overhead analysis + + Given the parameters above, intro circuit machines have an overhead of 11 + padding cells, and rendezvous circuit machines have an overhead of 4 + cpadding ells. . This means that for every intro and rendezvous circuit + there will be an overhead of 15 padding cells in average, which is about + 7.5kb. + + In the PrivCount paper [1] we learn that the Tor network sees about 12 + million successful descriptor fetches per day. We can use this figure to + assume that the Tor network also sees about 12 million intro and rendezvous + circuits per day. Given the 7.5kb overhead of each of these circuits, we get + that our padding machines infer an additional 94GB overhead per day on the + network, which is about 3.9GB per hour. + + XXX Isn't this kinda intense????? Using the graphs from metrics we see that + the Tor network has total capacity of 300 Gbit/s which is about 135000GB per + hour, so 3.9GB per hour is not that much, but still... + +7. Discussion + +7.1. Alternative approaches + + These machines try to hide onion service client-side circuits by obfuscating + their looks. This is a reasonable approach, but if the resulting circuits + look unlike any other Tor circuits, they would still be fingerprintable just + by that fact. + + Another approach we could take is make normal client circuits look like + onion service circuits, or just make normal clients establish fake onion + service circuits periodically. The hope here is that the adversary won't be + able to distinguish fake onion service circuits from real ones. This + approach has not been taken yet, mainly because it requires additional + WTF-PAD features and poses greater overhead risks. + +7.2. Future work + + As discussed in [SCOPE], this proposal only aims to hide some very specific + features of client-side onion service circuits. There is lots of work to be + done here to see what other features can be used to distinguish such + circuits, and also what other classifiers can be built using deep learning + and whatnot. + +--- + + [0]: https://www.usenix.org/node/190967 + https://blog.torproject.org/technical-summary-usenix-fingerprinting-paper + + [1]: "Understanding Tor Usage with Privacy-Preserving Measurement" + by Akshaya Mani, T Wilson-Brown, Rob Jansen, Aaron Johnson, and Micah Sherr + In Proceedings of the Internet Measurement Conference 2018 (IMC 2018).

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