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CATEGORIES:Computer Laboratory Security Group meeting present
 ations
SUMMARY:Hot or Not: Revealing Hidden Services by their Clo
 ck Skew - Steven J. Murdoch (Computer Laboratory\,
  University of Cambridge)
DTSTART;TZID=Europe/London:20061027T160000
DTEND;TZID=Europe/London:20061027T163000
UID:TALK5798AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/5798
DESCRIPTION:Location-hidden services\, as offered by anonymity
  systems such as Tor\, allow servers to be operate
 d under a pseudonym. As Tor is an overlay network\
 , servers hosting hidden services are accessible b
 oth directly and over the anonymous channel. Traff
 ic patterns through one channel have observable ef
 fects on the other\, thus allowing a service's pse
 udonymous identity and IP address to be linked. On
 e proposed solution to this vulnerability is for T
 or nodes to provide fixed quality of service to ea
 ch connection\, regardless of other traffic\, thus
  reducing capacity but resisting such interference
  attacks. However\, even if each connection does n
 ot influence the others\, total throughput would s
 till affect the load on the CPU\, and thus its hea
 t output. Unfortunately for anonymity\, the result
  of temperature on clock skew can be remotely dete
 cted through observing timestamps. This attack wor
 ks because existing abstract models of anonymity-n
 etwork nodes do not take into account the inevitab
 le imperfections of the hardware they run on. Furt
 hermore\, we suggest the same technique could be e
 xploited as a classical covert channel and can eve
 n provide geolocation.
LOCATION:Computer Laboratory\, William Gates Building\, Roo
 m FW11
CONTACT:Steven J. Murdoch
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