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65 lines
2.7 KiB
Plaintext
65 lines
2.7 KiB
Plaintext
Filename: 152-single-hop-circuits.txt
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Title: Optionally allow exit from single-hop circuits
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Version:
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Last-Modified:
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Author: Geoff Goodell
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Created: 13-Jul-2008
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Status: Closed
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Implemented-In: 0.2.1.6-alpha
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Overview
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Provide a special configuration option that adds a line to descriptors
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indicating that a router can be used as an exit for one-hop circuits,
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and allow clients to attach streams to one-hop circuits provided
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that the descriptor for the router in the circuit includes this
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configuration option.
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Motivation
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At some point, code was added to restrict the attachment of streams
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to one-hop circuits.
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The idea seems to be that we can use the cost of forking and
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maintaining a patch as a lever to prevent people from writing
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controllers that jeopardize the operational security of routers
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and the anonymity properties of the Tor network by creating and
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using one-hop circuits rather than the standard three-hop circuits.
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It may be, for example, that some users do not actually seek true
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anonymity but simply reachability through network perspectives
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afforded by the Tor network, and since anonymity is stronger in
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numbers, forcing users to contribute to anonymity and decrease the
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risk to server operators by using full-length paths may be reasonable.
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As presently implemented, the sweeping restriction of one-hop circuits
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for all routers limits the usefulness of Tor as a general-purpose
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technology for building circuits. In particular, we should allow
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for controllers, such as Blossom, that create and use single-hop
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circuits involving routers that are not part of the Tor network.
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Design
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Introduce a configuration option for Tor servers that, when set,
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indicates that a router is willing to provide exit from one-hop
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circuits. Routers with this policy will not require that a circuit
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has at least two hops when it is used as an exit.
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In addition, routers for which this configuration option
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has been set will have a line in their descriptors, "opt
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exit-from-single-hop-circuits". Clients will keep track of which
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routers have this option and allow streams to be attached to
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single-hop circuits that include such routers.
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Security Considerations
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This approach seems to eliminate the worry about operational router
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security, since server operators will not set the configuraiton
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option unless they are willing to take on such risk.
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To reduce the impact on anonymity of the network resulting
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from including such "risky" routers in regular Tor path
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selection, clients may systematically exclude routers with "opt
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exit-from-single-hop-circuits" when choosing random paths through
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the Tor network.
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