[tor-dev] Revising Proposal 140

Daniel Martí mvdan at mvdan.cc
Thu May 1 08:02:30 UTC 2014

Hello everyone,

Last week I introduced myself [0] on this list, shortly after being
accepted into GSoC to work on Consensus Diffs. My GSoC proposal is
heavily based on the Tor proposal #140 [1], which is close to being six
years old now.

This is why, after some discussion with Nick, Sebastian and Weasel (the
original author of the proposal), it became obvious that it needs some
revising. Here are the improvements we discussed on IRC:

* Microdescriptors didn't exist back then, so the proposal makes no
  mention of microdescriptor consensus diffs. We should support these

* Weasel added the 's' command just so that a line with just one dot
  could be produced. Since consensuses should never have such a line, I
  think it would be best to drop 's' and not support such a line as an
  input when generating the diffs.

* In response to my introduction mail, Ian mentioned that fetching a
  diff is leaking data about when you last used Tor. Nick proposed to
  have a time limit on these diffs, to e.g. 24 or 36 hours, which should
  mitigate this problem.

* Regarding their size, #140 suggests that they are not useful past 16
  hours. I thought we could compare the compressed size of the diffs
  when creating them, since they may be of use for a longer time. We
  could do this relative size limit first as well as the time limit
  mentioned above.

That is all that we came up with for now, what do you think? Ideas about
what might be missing or needing an update are welcome, of course :)


[0] https://lists.torproject.org/pipermail/tor-dev/2014-April/006744.html
[1] https://gitweb.torproject.org/torspec.git/blob_plain/refs/heads/master:/proposals/140-consensus-diffs.txt

Daniel Martí - mvdan at mvdan.cc - http://mvdan.cc/
PGP: A9DA 13CD F7A1 4ACD D3DE  E530 F4CA FFDB 4348 041C
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