[tor-bugs] #3460 [Tor Hidden Services]: Expand replay-detection window for HS INTRODUCE2 cells

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#3460: Expand replay-detection window for HS INTRODUCE2 cells
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 Reporter:  rransom              |          Owner:  rransom           
     Type:  task                 |         Status:  new               
 Priority:  normal               |      Milestone:  Tor: 0.2.2.x-final
Component:  Tor Hidden Services  |        Version:                    
 Keywords:                       |         Parent:                    
   Points:                       |   Actualpoints:                    
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 Currently, hidden services only accept a v3 `INTRODUCE2` cell from a
 client if the timestamp it contains is within 30 minutes of the service's
 current time, so that the service doesn't need to keep entries in its
 replay-detection cache for very long.  We should expand that window.

 But in order to figure out how large the window should be, we need some
 statistics for how many entries are stored in a popular hidden service's
 replay cache.  We should also investigate the typical lifetimes of HS
 descriptors and service-side introduction-point circuits, to find out
 whether we can remove the timestamp check entirely.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/3460>
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