[tor-bugs] #1839 [BridgeDB]: Rotate available bridges over time

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#1839: Rotate available bridges over time
-----------------------------+---------------------------------
     Reporter:  arma         |      Owner:  isis
         Type:  enhancement  |     Status:  assigned
     Priority:  normal       |  Milestone:
    Component:  BridgeDB     |    Version:
   Resolution:               |   Keywords:  easy, bridgedb-dist
Actual Points:               |  Parent ID:
       Points:               |
-----------------------------+---------------------------------
Changes (by isis):

 * cc: sysrqb (added)


Comment:

 During #4771, BridgeDB was changed to distribute a maximum of four sets of
 bridges to all Tor/proxy users during a time period. The way that this
 works is that the HMAC determining the client's position in the hashring
 is given:

 {{{
 known-proxy<EPOCH>GROUP
 }}}

 where `EPOCH` is the beginning of the current time period (this is the
 part that needs this rotation ticket done), and `GROUP` is calculated by
 `int(ipaddr.IPAddress(CLIENT_IP)) % 4`, such that all Tor/proxy users are
 split into four groups (effectively meaning that regardless of how many
 times one gets a new Exit node or proxy, there are only four sets of
 bridges available.

 Therefore, we ''absolutely need'' to be certain that periodic rotation is
 enabled now (it isn't), otherwise only four sets of bridges will go to all
 Tor/proxy users forever, and everyone will mail Join AOL! CDs and explody
 packages of glitter to me in their sheer anger and frustration.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/1839#comment:6>
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