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<blockquote type="cite">Today I actually tried to connect to it and it is possible to connect to the
<br />
bridge using the ORport.
<br />
But when I tried to start tor browser with this setting to use obfs4:
<br />
<br />
obfs4 12.345.67.89:1111 (only with the right numbers)</blockquote>
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it got stuck at "establishing an encrypted network connection".
<br />
I checked on canyouseeme.org and both the vanilla ORport and the obfs4 port
<br />
seem to be accessible from outside.</blockquote>
<br />
The obfs4 protocol needs to have not just the IP and port, but also
<br />
the shared secret.
<br />
<br />
For example, a valid obfs4 bridge line looks like:
<br />
<br />
obfs4 154.35.22.10:15937 8FB9F4319E89E5C6223052AA525A192AFBC85D55
cert=GGGS1TX4R81m3r0HBl79wKy1OtPPNR2CZUIrHjkRg65Vc2VR8fOyo64f9kmT1UAFG7j0HQ iat-mode=0
<br />
<br />
The other parameters are needed because the client needs to prove
<br />
knowledge of the shared secret before the bridge will admit to being a
<br />
bridge.
<br />
<br />
That's because one of the steps in the arms race has been "active probing"
<br />
by China, where they use DPI to notice connections that might be obfs4,
<br />
and then do their own follow-up connection speaking the obfs4 protocol,
<br />
and if it talks obfs4 back, they know they can block it:
<br />
https://www.freehaven.net/anonbib/#foci12-winter
<br />
<blockquote type="cite">My router is set to allow TCP and UDP on the port for obfs4.</blockquote>
<br />
obfs4 only needs TCP.</div>
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Thanks for your replies! :)
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Seems like I followed the instructions on <a target="_blank" rel="noreferrer noopener" href=
"https://www.torproject.org/docs/bridges.html.en">https://www.torproject.org/docs/bridges.html.en</a> and replaced
obfs3 with obfs4 without thinking xD.
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