[tor-bugs] #28655 [Obfuscation/BridgeDB]: If a bridge supports obfs4, don't give out its other flavors

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#28655: If a bridge supports obfs4, don't give out its other flavors
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 Reporter:  arma                  |          Owner:  sysrqb
     Type:  defect                |         Status:  new
 Priority:  Medium                |      Milestone:
Component:  Obfuscation/BridgeDB  |        Version:
 Severity:  Normal                |     Resolution:
 Keywords:                        |  Actual Points:
Parent ID:                        |         Points:
 Reviewer:                        |        Sponsor:  Sponsor19
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Comment (by dcf):

 Replying to [ticket:28655 arma]:
 > Second, it assumes that the FOCI paper is actually correct in its
 conclusions about how China has changed its blocking.

 Zhongjie Wang, Yue Cao, Zhiyun Qian, Chengyu Song, and Srikanth V.
 Krishnamurthy observed the same in their
 [https://censorbib.nymity.ch/#Wang2017a INTANG paper], §7.3:
 > Meanwhile, any hidden bridge nodes requested by the remaining 7 vantage
 points triggers active probing [‌[https://censorbib.nymity.ch/#Ensafi2015b
 13], [https://censorbib.nymity.ch/#Winter2012a 31]‌] and are immediately
 blocked by the GFW, ''i.e.'', any node in China can no longer connect to
 this IP via any port. This is very different from what was previously
 reported ''i.e.'', the GFW only blocks the Tor port on that hidden bridge
 [‌[https://censorbib.nymity.ch/#Winter2012a 31]‌], and could cause
 collateral damage as the Amazon EC2 IPs are recycled. We test 5 different
 hidden bridge IPs and find no exceptions so far.

 This test was done between May 10 and May 18, 2017, according to my
 correspondence with the authors.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/28655#comment:2>
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