[tahoe-lafs-trac-stream] [tahoe-lafs] #2018: padding to hide the size of plaintexts

[tahoe-lafs]

#2018: padding to hide the size of plaintexts
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     Reporter:  zooko    |      Owner:
         Type:           |     Status:  new
  enhancement            |  Milestone:  undecided
     Priority:  normal   |    Version:  1.10.0
    Component:  code-    |   Keywords:  confidentiality privacy compression
  encoding               |  newcaps
   Resolution:           |
Launchpad Bug:           |
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Comment (by nickm):

 Here's how to do the analysis.

 Look at what information the attacker sees over time, and what the
 attacker is trying to learn.  Consider how fast they can learn what
 they like as Tahoe stands today.  Then consider how fast they can
 learn that with the proposed padding scheme.

 Generally, padding many things to the same size tends to work better
 than adding random amounts of padding to a lot of things. In the "pad
 to same size" case, the attacker learns less from seeing the size of a
 single object.

 Don't forget object linkability in your analysis.  That is, if certain
 messages are likelier to be received together than two messages chosen
 at random, then the attacker can make inferences over time, so you
 can't just look at single-object probabilities in isolation.

 Feel free to share this message wherever it will do good.

-- 
Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/2018#comment:3>
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