wiki:org/meetings/2014WinterDevMeeting/notes/GuardDesign

Guard nodes

Abstract: What is to be done?

Minutes

One guard / guard sets

  • Perhaps we should go to 1 guard by default.
  • Alternatively, we could go with "guard sets" and similar ideas, but those have deep gaps and unanswered questions.
  • We should probably increase the rotation period.
  • To make it safe to increase the rotation period, perhaps we should add a weight parameter describing how much of the last rotation period you've been a guard. Use that when picking non-guard nodes for bw-relevant activities.
  • Perhaps we should raise the threshold of bandwidth required to be a guard such that...
    • ...the smallest guard is a non-tiny fraction of the whole network ?
    • ...the smallest guard is not too slow
  • Could there be a user parameter to raise guard bw threshold

Guards and identity

  • Hey, should there be a different set of guards per identity?
  • Or a different tor state per identity
    • see #10969. See wiki link from there. See tordyguards
    • way to kill state reload state and restart tor
    • need way to not have Tor launch a connection to an old guard before it realizes it's moved.
    • need way to avoid dhcp attack
      • networkmanager / systemd integration?
      • what is the dhcp attack? would an attacker in a position to manipulate your dhcp leases gain anything by causing you to keep picking new guards until you pick one of theirs? (wouldn't it be easier to just become the default gateway and then do whatever attacks they might do as a guard from that position instead?)
  • Separate guards per isolation profile. That would be neat.
    • Can't do in full. since there are infinite isolation profiles.
    • But it would be cool to separate hidden services from other stuff
    • And it would be cool to allow separation via different socksports, etc

How many guard are used at once?

  • Limit how many guards a user gets/tries at one time?
    • If you get a whole bunch of guards, probably your connection is down...
    • Or maybe somebody's denying your connections till you pick a good guard.
  • "Kill the node and see where users scatter" attack has some complex solutions.
    • fingers to pick next guard from a small set?
    • decide these fingers based on unpredictable shuffle of net?

When are guards chosen?

When to choose sets of guards?

  • option 1: choose more guards, use one at a time. (Needs coding)
  • option 2: choose next guard at time of first-guard failure.

Missing proposals

  • Limit how many guards can go down (see sniper attack)
  • Should guard rotation period be consensus parameter?
  • New proposal: "i couldn't consense" statement. Anybody could write.
  • New proposal: "consensus hash chain". Anybody could write.

Guard enumeration

Guard enumeration, maybe 9 months is far easier then 2 months. Especially if Tor is used infrequently. We need a solution for guard enumeration:

  • 2-hop cascades?
  • pathsel is an abstraction layer.

arma matters

arma blocks unless we have a way to say that the users don't mostly get shoved onto shitty guards.

Open questions:

  • why does arma have so many guards in his state file?
  • why are his guards not in sequential order????????

Next steps

Next steps:

  • Expand above into longer nodes, proposal. (Nick, Nick, George)
  • Investigate questions, issues.
  • Profit!
Last modified 4 years ago Last modified on Jun 24, 2014, 2:12:38 AM