This question already has an answer here:
I recently become interested in researching about the Tor network and as I read, there are 9 directory authorities which are hard-coded into the Tor software and they are like phone-book which gives the client a random list of tor relays and servers and a list of them is also available at : https://atlas.torproject.org/#search/flag:authority
In other document I read about if all of this Directory Servers become compromised then relays work as a cache to give the clients a list of Tor servers so it is probably not possible to shutdown Tor network completely without Directory Authorities (another article said that clients also have a small cache of Tor Servers addresses).
So my question is what could they do to circumvent filtering of above addresses in countries which completely filter Tor Network traffic ?
In other words what do obfuscation methods (like obfs4) do to get a list of Tor relays and servers when the above hard-coded addresses is censored and the client never talks to Directory Authorities before ?