[tor-bugs] #13727 [BridgeDB]: BridgeDB should not distribute Tor Browser's default bridges

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#13727: BridgeDB should not distribute Tor Browser's default bridges
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 Reporter:  isis                        |          Owner:  isis
     Type:  defect                      |         Status:  new
 Priority:  normal                      |      Milestone:
Component:  BridgeDB                    |        Version:
 Keywords:  bridgedb-dist, tbb-bridges  |  Actual Points:
Parent ID:                              |         Points:
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 From #13504, we started distributing, in Tor Browser as the sets of
 'default' bridges, only bridges which report their descriptors to the
 BridgeAuthority, causing those descriptors to eventually be sent through
 BridgeDB to the Metrics servers. This was done to obtain more accurate
 Metrics on bridge usage, since it is believed that most bridge users are
 currently using the default bridges.

 Robert Ransom points out that we don't want BridgeDB to distribute these
 default Tor Browser bridges. The reasons are similar to why we don't want
 to initialise/use multiple types of PTs at the same time in Tor Browser:
 Using a TB-default bridge, presumedly mixed in with other non-TB-default
 bridges obtained from BridgeDB, would signal to anyone watching for use of
 the TB-default bridges that the other addresses are Tor bridges, thus
 potentially endangering:

  1. the user, Alice, who was accidentally given the TB-default bridge by
 BridgeDB, because she may now find that all her bridges are suddenly
 blocked,
  2. Alice's other bridges, which are at increased risk of being blocked by
 whoever is watching Alice,
  3. and the other users of Alice's other bridges.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/13727>
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