I am working on setting up a Tor obfs4 bridge. If I understand it correctly ServerTransportListenAddr allows me to choose a port (and an IP) to bind the Pluggable Transport to. However I also need to set an ORPort and Tor logs that it does reachability tests.

Doesn't this defeat the whole point of using a pluggable transport and obfs4 in particular? Couldn't an attacker just look for the normal ORPort and thereby detect the bridge as such?

Do I need to forward the ORPort?


The attacker wouldn't be able to find you if nobody tries to connect to your ORPort. If you didn't publish the bridge descriptor, nobody will know your ORPort.

  • But then there are a few open questions: Why not randomize it and why does it have to be open then (having reachability tests)?
    – meee
    Oct 18 '14 at 17:37
  • It can be random (just input random number) and even unreachable. Even if reachability test fails, your bridge will still run well.
    – nobody
    Oct 19 '14 at 1:41
  • Okay, thank you. And it will still be propagated to bridge authorities?
    – meee
    Oct 19 '14 at 10:05
  • It looks like there is a ticket for this
    – meee
    Oct 19 '14 at 11:06

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