[tor-bugs] #30716 [Circumvention/Obfs4]: Improve the obfs4 obfuscation protocol

[Tor Bug Tracker & Wiki]

#30716: Improve the obfs4 obfuscation protocol
------------------------------------------------+--------------------------
 Reporter:  phw                                 |          Owner:  phw
     Type:  task                                |         Status:  assigned
 Priority:  High                                |      Milestone:
Component:  Circumvention/Obfs4                 |        Version:
 Severity:  Normal                              |     Resolution:
 Keywords:  sponsor28, anti-censorship-roadmap  |  Actual Points:
Parent ID:                                      |         Points:  20
 Reviewer:                                      |        Sponsor:
                                                |  Sponsor28-must
------------------------------------------------+--------------------------

Comment (by dcf):

 The
 [https://gitlab.com/yawning/obfs4/blob/obfs4proxy-0.0.10/doc/obfs4-spec.txt#L237
 obfs4 framing format] is pretty nice, in that is allow arbitrary shaping:
 both client and server can send any amount of data, at any time. The only
 exception is at one point during the handshake: after the client has sent
 the MAC indicating the end of its padding, the client must remain silent
 until after the server has sent ''its'' part of the handshake. You can see
 the gap in the bottom two graphs at
 https://people.torproject.org/~dcf/obfs4-timing/.

 So one desideratum from me is that the protocol should allow either side
 to send any amount of data at any time, and have it correctly interpreted
 as padding or meaningful data. Ideally it should even be possible for the
 server to send data before the client has sent anything.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/30716#comment:2>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online