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[liberationtech] [tor-talk] Tor Weekly News — October 16th, 2013

Eugen Leitl eugen at
Wed Oct 16 06:21:09 PDT 2013

----- Forwarded message from Lunar <lunar at> -----

Date: Wed, 16 Oct 2013 14:32:48 +0200
From: Lunar <lunar at>
To: tor-news at, tor-talk at
Subject: [tor-talk] Tor Weekly News — October 16th, 2013
Message-ID: <20131016123248.GB19497 at loar>
User-Agent: Mutt/1.5.21 (2010-09-15)
Reply-To: tor-talk at

Tor Weekly News                                       October 16th, 2013

Welcome to the sixteenth issue of Tor Weekly News, the weekly newsletter
that covers what’s happening in the venerable Tor community.

Making hidden services more scalable and harder to locate

Christopher Baines started a discussion [1] on tor-dev on the scaling
issues affecting the current design of Tor hidden services. Nick
Mathewson later described Christopher’s initial proposal as “single
hidden service descriptor, multiple service instances per intro point”
along with three other alternatives. Nick and Christopher also teamed up
to produce a set of seven goals that a new hidden service design should
aim for regarding scalability.

There’s probably more to discuss regarding which goals are the most
desirable, and which designs are likely to address them, without — as
always — harming anonymity.

George Kadianakis also called for help [2] concerning “the guard
enumeration attack that was described by the ‘Trawling for Tor Hidden
Services: Detection, Measurement, Deanonymization’ paper (in section
VII)” [3].

The most popular solution so far seems to be enabling a client or hidden
service to reuse some parts of a circuit that cannot be completed
successfully in order to connect to new nodes. This should “considerably
slow the attack” [4], but “might result in unexpected attacks” as George
puts it.

These problems could benefit from everyone’s attention. Free to read the
threads in full and offer your insights!


Detecting malicious exit nodes

Philipp Winter asked [5] for feedback on the technical architecture of
“a Python-based exit relay scanner which should detect malicious and
misbehaving exits.”

Aaron took the opportunity to mention his plans [6] to leverage the work
done as part of OONI [7] to detect network interference. Aaron’s
intention is to “provide Tor network tests as part of ooni-probe’s
standard set of tests, so that many individuals will measure the Tor
network and automatically publish their results, and so that current and
future network interference tests can be easily adapted to running on
the Tor network.”

Detecting misbehaving exits so they can be flagged “BadExit” [8] by the
operators of the directory authorities is important to make every Tor
user safer. Getting more users to run tests against our many exit nodes
would benefit everyone — it makes it more likely that bad behavior will
be caught as soon as possible.


Hiding location at the hardware level

One of Tor’s goals is to hide the location of its users, and it does a
reasonably good job of this for Internet connections. But when your
threat model includes an adversary that can monitor which equipment is
connected to a local network, or monitor Wi-Fi network probes received
by many access points, extra precautions must be taken.

Ethernet and Wi-Fi cards ship with a factory-determined hardware address
(also called a MAC address) that can uniquely identify a computer across
networks. Thankfully, most devices allow their hardware address to be
changed by an operating system.

As the Tails live operating system aims to protect the privacy and
anonymity of its users, it has long been suggested [9] that it should
automatically randomize MAC addresses. Some important progress has been
made, and this week anonym requested comments [10] on a detailed
analysis of why, when and how Tails should randomize MAC addresses.

In this analysis, anonym describes a Tails user wanting to hide their
geographical movement and not be identified as using Tails, but who also
wants to “avoid alarming the local administrators (imagine a situation
where security guards are sent to investigate an ‘alien computer’ at
your workplace, or similar)” and “avoid network connection problems due
to MAC address white-listing, hardware or driver issues, or similar”.

The analysis then tries to understand when MAC address should be
randomized depending on several combinations of locations and devices.
The outcome is that “this feature is enabled by default, with the
possibility to opt-out.” anonym then delves into user interface and
implementation considerations.

If you are interested in the analysis, or curious about how you could
help with the proposed implementation, be sure to have a look!


Tor Help Desk Roundup

The Tor project wishes to expand its support channels to text-based
instant messaging as part of the Boisterous Otter [11] project. Lunar
and Colin C. came up with a possible implementation [12] based on the
XMPP protocol, Prosody [13] for the server side, and Prodromus [14] as
the basis for the web based interface.

This week, multiple people asked if Tor worked well on the Raspberry Pi.
Although the Tor Project does not have any documentation directed
specifically at the Raspberry Pi (yet!), the issue was raised on Tor’s
StackExchange page [15]. Tor relay operators are encouraged to share
their experiences or ask for help on the tor-relays public mailing
list [16].


Miscellaneous news

Ten years ago, on October 8th, 2003, Roger Dingledine announced [17] the
first release of tor as free software on the or-dev mailing list.


Damian Johnson announced [18] the release of Stem 1.1.0 [19]. The new
version of this “Python library for interacting with Tor” adds remote
descriptor fetching, connection resolution and a myriad of small
improvements and fixes.


Arlo Breault sent out a detailed plan on how Mozilla Instantbird could
be turned into the Tor Messenger [20]. Feedback would be welcome,
especially with regard to sandboxing, auditing, and internationalization
for right-to-left languages.


The Spanish and German version of the Tails website are outdated and may
soon be disabled [21]. Now is a good time to help [22] if you want to
keep those translations running!


adrelanos announced [23] the release of Whonix 7, an operating system
“based on Tor […], Debian GNU/Linux and the principle of security by
isolation.” The new version includes tor 0.2.4, Tor Browser as the
system default browser and a connection wizard, among other changes.


Lunar sent out a report about the Dutch OHM2013 hacker camp [24] that
took place in August.


Philipp Winter, Justin Bull and rndm made several improvements to
Atlas [25], the web application for learning more about
currently-running Tor relays. The HSDir flag is now properly
displayed [26], full country names and flags are shown instead of
two-letter codes [27] and it’s now easier to find out how long a relay
has been down [28].


ra, one of Tor’s former GSoC students, proposed a patch [29] to add a
command to the Tor control protocol asking tor to pick a completely new
set of guards.


starlight shared some simple shell snippets [30] that connect to the Tor
control port in order to limit the bandwidth used by a relay while
running backups.


Upcoming events

Nov 04    | Workshop on Privacy in the Electronic Society
          | Berlin, Germany
Nov 04-05 | 20th ACM Conference on Computer and Communications Security
          | Berlin, Germany

This issue of Tor Weekly News has been assembled by Lunar, Matt Pagan,
harmony, dope457, Damian Johnson and Philipp Winter.

Want to continue reading TWN? Please help us create this newsletter.
We still need more volunteers to watch the Tor community and report
important news. Please see the project page [31], write down your name
and subscribe to the team mailing list [32] if you want to get involved!


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----- End forwarded message -----
Eugen* Leitl <a href="">leitl</a>
ICBM: 48.07100, 11.36820
AC894EC5: 38A5 5F46 A4FF 59B8 336B  47EE F46E 3489 AC89 4EC5

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