commit 73b45c0680c865bae64936f0bd41c3757bdf7d2f Author: Mike Perry <mikeperry-git@torproject.org> Date: Fri Oct 31 22:51:21 2014 -0700 Mention OS type fingerprinting in the fingerprinting section. --- design-doc/design.xml | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/design-doc/design.xml b/design-doc/design.xml index b8c67d9..9ff1b89 100644 --- a/design-doc/design.xml +++ b/design-doc/design.xml @@ -1902,6 +1902,40 @@ fingerprinting: timestamp quantization and jitter. We have no implementation as of yet. </para> </listitem> + <listitem>Operating System type fingerprinting + <para> + +As we mentioned in the introduction of this section, OS type fingerprinting is +currently considered a lower priority, due simply to the numerous ways that +characteristics of the Operating System type may leak into content, and the +comparatively low contribution of OS to overall entropy. In particular, there +are likely to be many ways to measure the differences in widget size, +scrollbar size, and other rendered details on a page. Also, directly exported +OS routines, such as the Math library, expose differences in their +implementations due to these results. + + + </para> + <para><command>Design Goal:</command> + +We intend to reduce or eliminate OS type fingerprinting to the best extent +possible, but recognize that the effort for reward on this item is not as high +as other areas. The entropy on the current OS distribution is somewhere around +2 bits, which is much lower than other vectors which can also be used to +fingerprint configuration and user-specific information. + + </para> + <para><command>Implementation Status:</command> + +We have no defenses deployed that address OS type fingerprinting, but nothing +else. Several defenses may help also mitigate it, in addition to reducing a +lot more entropy elsewhere. You can see the major areas of OS fingerprinting +we're aware of using the tag <ulink +url="https://trac.torproject.org/projects/tor/query?keywords=~tbb-fingerprinting-os">tbb-fingerprinting-os +on our bugtracker</ulink>. + + </para> + </listitem> </orderedlist> </sect3> <para>