Opened 3 years ago

#13336 new enhancement

Reduce centralization that allows enumeration of flashproxies

Reported by: arma Owned by: dcf
Priority: Medium Milestone:
Component: Archived/Flashproxy Version:
Severity: Keywords:
Cc: Actual Points:
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Description

One of the cool side effects of the Flashproxy design is that its transient addresses provide a buffer between the known IP addresses of the Tor network and the clients who use them. So some classes of global surveillance-oriented rules will have a tougher time enumerating those clients.

My use case is against an adversary who builds a list of IP addresses and then logs all packets for all flows that are to or from any of these IP addresses. If that adversary later learns about an IP address whose flows it wishes it had logged, it can't go back in time and get the whole flow.

That is, picture an adversary who wants to write down all flows of all Tor users, but can't afford to write down all flows of all Internet users. Flashproxy is interesting in that when you see the Tor client <-> flashproxy flow, you don't yet realize it's worth writing down. Unless somehow you learned beforehand that that flashproxy was worth watching.

(I don't mean to say that defeating this adversary will defeat all large surveilling adversaries. But I think this one is still a worthwhile step.)

So, what are the centralized components in the Flashproxy design that would allow the attacker to preemptively put a list of all flashproxy IP addresses on his list?

One is the facilitator -- if you watch connections to it, you see all the flash proxies every time they ask if there are new clients that need connect-backs -- potentially long before they actually hear about a client and connect to it. Can we reduce this vulnerability?

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