Re: [tor-bugs] #7202 [Tor]: Implement ntor handshake or its successor

["Tor Bug Tracker & Wiki" <blackhole@xxxxxxxxxxxxxx>]

#7202: Implement ntor handshake or its successor
--------------------------------+-------------------------------------------
 Reporter:  karsten             |          Owner:                    
     Type:  project             |         Status:  needs_review      
 Priority:  normal              |      Milestone:  Tor: 0.2.4.x-final
Component:  Tor                 |        Version:                    
 Keywords:  SponsorZ tor-relay  |         Parent:                    
   Points:                      |   Actualpoints:                    
--------------------------------+-------------------------------------------

Comment(by rransom):

 Replying to [comment:18 nickm]:
 > Replying to [comment:16 mikeperry]:
 > > Thanks for the above. I'm reviewing the thread now. I just noticed
 this from Ian:
 > >
 > > > The directory authorities should probably checks the B's anyway,
 just to be sane.  They should all have order exactly p_1, so check that
 EXP(B,8) is not O, and check that EXP(B,p_1) is O.
 > >
 > > It seems everybody agreed this was a good idea, but I don't see these
 checks in the ntor branch.
 >
 > I didn't see it as a terribly great idea; it doesn't achieve anything
 security-wise.  If a malicious router wanted to use a broken key in this
 way, it wouldn't actually be achieving anything other than letting anybody
 else authenticate as it.  But a malicious router could also just publish
 or share its private key or session keys, and thereby achieve the same
 result without getting detected.  This is useful to check for a particular
 set of bug in the routers, nothing more.
 >
 > We can add another patch if need be, I guess.  Can somebody tell me the
 right value for p_1, or do I have to dig it out myself.

 It's on page 8 of [http://cr.yp.to/ecdh/curve25519-20060209.pdf], but you
 can't raise a point to a power divisible by p_1 without modifying the
 Curve25519 software.  Fortunately, ''none'' of this key-checking crap is
 necessary, or even useful, for ntor.

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/7202#comment:20>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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