[tor-bugs] #23420 [Core Tor/Tor]: prop224: Pad RENDEZVOUS1 cell to match legacy cell length

Tor Bug Tracker & Wiki blackhole at torproject.org
Wed Sep 20 12:06:50 UTC 2017


#23420: prop224: Pad RENDEZVOUS1 cell to match legacy cell length
--------------------------------------------+------------------------------
 Reporter:  asn                             |          Owner:  dgoulet
     Type:  defect                          |         Status:  needs_review
 Priority:  Medium                          |      Milestone:  Tor:
                                            |  0.3.2.x-final
Component:  Core Tor/Tor                    |        Version:
 Severity:  Normal                          |     Resolution:
 Keywords:  prop224, prop224-extra, tor-hs  |  Actual Points:
Parent ID:                                  |         Points:  1
 Reviewer:                                  |        Sponsor:
--------------------------------------------+------------------------------

Comment (by nickm):

 So, IIUC, the "algebraic structure" in question here is just that real
 values of g^y^ will always be between 2 and p-1 (inclusive).  But since p
 is very close to 2^1024^, nearly all values will pass that test.  (Random
 junk will fail with probability approximately 2^-66^.)

 The tap/ntor argument is stronger.

 On the other hand, just padding with random bytes costs us almost nothing.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/23420#comment:6>
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