[tor-bugs] #5011 [Pluggable transport]: Discuss possible designs for an external program that discovers bridge addresses to tell Tor about them

[Tor Bug Tracker & Wiki]

#5011: Discuss possible designs for an external program that discovers bridge
addresses to tell Tor about them
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 Reporter:  karsten              |          Owner:  mikeperry                
     Type:  task                 |         Status:  new                      
 Priority:  normal               |      Milestone:  Sponsor F: March 15, 2012
Component:  Pluggable transport  |        Version:                           
 Keywords:  MikePerry201203      |         Parent:  #5010                    
   Points:                       |   Actualpoints:                           
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Comment(by rransom):

 Replying to [comment:6 seaman]:
 > Regarding the design of BridgeFinder, I suggest that it contains a
 plugin system in order to allow different inputs. In
 https://trac.torproject.org/projects/tor/ticket/5096 it is proposed to use
 QR codes but I think that this should not be the only option.

 #5096 is not related to this ticket.

 > One problem with QR codes is that they are clearly describing something
 that is hidden. So instead I propose an additional plugin that does
 steganography. In more detail I'm thinking of image steganography
 (although at a later stage one could add audio/video).

 Don't forget about steganography in text, or just indistinguishable-from-
 random bits in plain sight where the censors would expect to see bits that
 they cannot afford to distinguish from random.

 Also, this ticket isn't about writing a 'BridgeFinder' itself; it's about
 designing the interface that every BridgeFinder should use to tell Tor
 about a bridge.

 > The basic idea:
 > A list of bridge addresses get sent to a trusted person. This person
 encodes the bridge addresse(s) into an image and sends them to a friend.
 This friend then decodes the bridge address contained in the image and
 uses it to connect to TOR (via BridgeFinder).

 `s/TOR/Tor/`

 > A bit more specific:
 > # The encoding will not alter the image signficantly so that it appears
 to be a valid unsuspicious data exchange (e.g. a holiday snapshot, avatar,
 signature).
 > # To encode the image a password needs to be entered that is known by
 both ends. Password suggestion:
 > # # a complex password known by both parties

 There are easier ways than image steganography to transmit a piece of
 information to a user using a pre-shared secret.

 > # # name of a significant object in the image (this would allow external
 people easier access, on the other hand it would also allow the use of
 image sharing websites and blogs, automatic algorithms (object detection)
 to treat large amounts of images would be difficult).

 This raises the issue that different people will describe an image (or an
 object in an image) using different texts.

 > # The decoding process must be computationally expensive in order to
 avoid dictonary attacks.
 > # The algorithm for decoding contains automatic error correction as well
 as data verification.
 >
 > Let me know what you think about this idea. If it is worth pursuing I
 can do the coding.

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/5011#comment:7>
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