[tor-bugs] #2435 [Metrics]: Preserving hashed IP addresses in sanitized bridge descriptors

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#2435: Preserving hashed IP addresses in sanitized bridge descriptors
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  Reporter:  karsten      |              Owner:  karsten 
      Type:  enhancement  |             Status:  assigned
  Priority:  normal       |          Milestone:          
 Component:  Metrics      |            Version:          
  Keywords:               |             Parent:          
    Points:               |   Actualpointsdone:          
Pointsdone:               |       Actualpoints:          
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Changes (by karsten):

  * status:  new => assigned


Comment:

 Yesterday I finished the implementation of hashed IP addresses in metrics-
 db (#2505).  I also sanitized some old bridge descriptors from 2008 with
 the new algorithm last night.

 Here's an early analyis of sanitized bridge descriptors containing IP
 address hashes.  The idea of the analysis is to compare unique IP
 addresses of a bridge compared to the number of statuses that contain this
 bridge.

 There are two graphs in the attachment.  The first graph shows a scatter
 plot of unique IP addresses and days of operation.  Only bridges with 24
 hours of operation are shown.  There is an accumulation of points at the
 lower left of the graph which are bridges with only a few days of bridge
 operation.  These bridges are probably not as useful for bridge users,
 because they are unavailable most of the time.  In contrast to that, the
 accumulation of points with almost 30 days of operation and only very few
 unique IP addresses indicates stable bridges on static IP addresses that
 are probably most useful for bridge users.  Points close to the dashed
 line indicate bridges that change their IP address once a day.  Points
 above the dashed line are probably not as useful for clients, too, because
 they change their IP address more than once per day.  These bridges are
 only useful if bridge users download new bridge descriptors for known
 bridges from the bridge authority.

 The second graph shows the cumulative fraction of bridges having a given
 number of unique IP addresses per day.  Again, the dashed line indicates
 bridges on dynamic IP addresses that change their IP address once a day.
 Two thirds of the bridges either have static IP addresses or change their
 address at most once a day.  This leaves us with one third of bridges
 changing their IP address more often than that.

 The next steps are:

  - Update the specification-like description of our the sanitizing process
 [https://metrics.torproject.org/papers/data-2010-12-29.pdf here].
  - Post the sanitized descriptors from November 2008 to or-dev for others
 to look.
  - Sanitize the 2.5 years of descriptors that we have once again and make
 them available on the metrics website.

 I'm planning to do the first two items today and publish the sanitized
 descriptors next Tuesday (assuming the sanitizing process finishes by
 then).

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/2435#comment:3>
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