[tor-bugs] #16646 [Tor]: Cannibalized intro point circuits are now 4 hops, instead of 3 (HS-side)

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#16646: Cannibalized intro point circuits are now 4 hops, instead of 3 (HS-side)
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 Reporter:  asn                          |          Owner:
     Type:  defect                       |         Status:  new
 Priority:  normal                       |      Milestone:
Component:  Tor                          |        Version:  Tor: 0.2.7
 Keywords:  tor-hs SponsorR performance  |  Actual Points:
Parent ID:                               |         Points:
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 The fix of #16260 makes hidden services establish a 4-hop introduction
 circuit, if they cannibalized during introduction circuit construction.

 This was done mainly to prevent circuit fingerprinting according to the
 latest USENIX paper, but it's unclear whether making only this change
 helps with anything.

 Hence, the performance penalty of 4-hops might be more important here.

 Another question, is how often do introduction circuits get cannibalized?
 It might be that it often happens, since this step is done in the very
 beginning when there are a few internal circuits lying around. But I might
 be very wrong.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/16646>
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