4 ms·

What specifically about TOR's TLS stream allows it to be identified as TOR traffic? The article simply says to load pcap files into the tool ... Makes me feel

What specifically about TOR's TLS stream allows it to be identified as TOR traffic? The article simply says to load pcap files into the tool ... Makes me feel like reading the article was a waste of time. I want technical details.

nitrogen 14y ago
My guess is that the timing, relative sizes, and/or destinations of packets sent distinguish one from the other.
jlgaddis 14y ago
Exactly, there's nothing really useful in this article. For 900 EUR, however, you can buy yourself a copy of their tool.
- pudquick 14y ago
  100% agree about the uselessness of the article. If I were to take a stab in the dark about how the tool is doing it, though - based on their "statistical" analysis comment, my guess is they're measuring sustained traffic levels / TCP connection duration. Your average encrypted web session won't look anything similar to a command-and-control bot calling home over Tor to some irc server (which is their example usage for the tool). Possibly including "known" Tor node IP addresses, as well. In addition, there was that Ethopian DPI filtering project against Tor that happened last summer (https://blog.torproject.org/blog/update-censorship-ethiopia https://blog.torproject.org/blog/update-censorship-ethiopia), with the Tor Project thinking they'd somehow fingerprinted some aspect of their TLS handshake. Maybe this knowledge is spreading.
cwu225 14y ago
packet sizes and inter-packet timings. This paper might peak your interests http://cacr.uwaterloo.ca/techreports/2012/cacr2012-08.pdf http://cacr.uwaterloo.ca/techreports/2012/cacr2012-08.pdf . It tries to obfuscate the network traffics by morphing them so they statistically look like Skype Traffic. They even open sourced their code at http://crysp.uwaterloo.ca/software/CodeTalkerTunnel.html http://crysp.uwaterloo.ca/software/CodeTalkerTunnel.html
h72a 14y ago
Tor's TLS handshake exhibits a number of peculiarities which distinguishes it from HTTPS. The cipher list inside the TLS client hello used to be a (almost?) unique (see http://www.cs.kau.se/philwint/static/gfc/ http://www.cs.kau.se/philwint/static/gfc/ ) and the SNI contains a random bogus domain.
nitrogen 14y ago
Dead comment from h72a (brand new account; possibly double-posted and deleted the wrong one?): h72a 14 minutes ago | link [dead] Tor's TLS handshake exhibits a number of peculiarities which distinguishes it from HTTPS. The cipher list inside the TLS client hello used to be a (almost?) unique (see http://www.cs.kau.se/philwint/static/gfc/ http://www.cs.kau.se/philwint/static/gfc/ ) and the SNI contains a random bogus domain.

nitrogen 14y ago

My guess is that the timing, relative sizes, and/or destinations of packets sent distinguish one from the other.

jlgaddis 14y ago

Exactly, there's nothing really useful in this article. For 900 EUR, however, you can buy yourself a copy of their tool.

pudquick 14y ago
100% agree about the uselessness of the article. If I were to take a stab in the dark about how the tool is doing it, though - based on their "statistical" analysis comment, my guess is they're measuring sustained traffic levels / TCP connection duration. Your average encrypted web session won't look anything similar to a command-and-control bot calling home over Tor to some irc server (which is their example usage for the tool). Possibly including "known" Tor node IP addresses, as well. In addition, there was that Ethopian DPI filtering project against Tor that happened last summer (https://blog.torproject.org/blog/update-censorship-ethiopia https://blog.torproject.org/blog/update-censorship-ethiopia), with the Tor Project thinking they'd somehow fingerprinted some aspect of their TLS handshake. Maybe this knowledge is spreading.

cwu225 14y ago

packet sizes and inter-packet timings. This paper might peak your interests http://cacr.uwaterloo.ca/techreports/2012/cacr2012-08.pdf http://cacr.uwaterloo.ca/techreports/2012/cacr2012-08.pdf . It tries to obfuscate the network traffics by morphing them so they statistically look like Skype Traffic. They even open sourced their code at http://crysp.uwaterloo.ca/software/CodeTalkerTunnel.html http://crysp.uwaterloo.ca/software/CodeTalkerTunnel.html

h72a 14y ago

Tor's TLS handshake exhibits a number of peculiarities which distinguishes it from HTTPS. The cipher list inside the TLS client hello used to be a (almost?) unique (see http://www.cs.kau.se/philwint/static/gfc/ http://www.cs.kau.se/philwint/static/gfc/ ) and the SNI contains a random bogus domain.

nitrogen 14y ago

Dead comment from h72a (brand new account; possibly double-posted and deleted the wrong one?): h72a 14 minutes ago | link [dead] Tor's TLS handshake exhibits a number of peculiarities which distinguishes it from HTTPS. The cipher list inside the TLS client hello used to be a (almost?) unique (see http://www.cs.kau.se/philwint/static/gfc/ http://www.cs.kau.se/philwint/static/gfc/ ) and the SNI contains a random bogus domain.