[tor-bugs] #1796 [Tor - Relay]: write-history and read-history in extra-infos leaks the relay's used bandwith if the bandwidth limit is changed

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#1796: write-history and read-history in extra-infos leaks the relay's used
bandwith if the bandwidth limit is changed
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 Reporter:  lancelot666       |        Type:  defect                    
   Status:  new               |    Priority:  minor                     
Milestone:                    |   Component:  Tor - Relay               
  Version:  Tor: unspecified  |    Keywords:  write-history read-history
   Parent:                    |  
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 If a user changes the bandwidth limit to a different value, the next
 update of the write/read-history (after a reload of the config) contains
 different values. By the difference of the values an attacker could infer
 how much bandwidth the user used by himself.

 Lets assume the extra info reports 18432000 (B) for a 15 min period. After
 increasing the bandwidth limit and reloading the server, the next update
 reports 23404544 (B) for the same 15 min period. Thus, an attacker can
 infer how much bandwidth the user/relay used by its own in this period.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/1796>
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