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SUMMARY:Peer-to-peer network topologies and anonymity - Nikita Borisov\, E
 lectrical and Computer Engineering Department\, University of Illinois at 
 Urbana-Champaign
DTSTART:20060908T150000Z
DTEND:20060908T160000Z
UID:TALK5479@talks.cam.ac.uk
CONTACT:Saar Drimer
DESCRIPTION:Peer-to-peer networks\, due to their decentralized constructio
 n\, are a natural platform for anonymous communication and large-scale p2p
  networks may be the key to widespread deployment of anonymous communicati
 ons technologies. In order to be scalable\, however\, p2p networks must ma
 intain a limited view of the network\, thereby creating a restricted topol
 ogy graph of nodes that can communicate with each other. As all communicat
 ion must follow paths within the graph\, we study the information that can
  be learned about the origin of a path based on observing intermediate nod
 es. We use both graph models and simulations in our analysis.\n\nIn our wo
 rk\, we contrast structured networks\, where the topology of the graph fol
 lows a mathematical model\, and unstructured ones\, where arbitrary connec
 tions can be made. Unstructured networks often develop an emergent power-l
 aw topology\; we have found that such topologies are a detriment for anony
 mity because they have poor mixing (paths remaining correlated to their st
 arting point after a large number of hops) and because the high-degree nod
 es can be subject to a targeted attack. We show that effective attacks aga
 inst such networks can be carried out with only a moderate number of compr
 omised nodes and without a global view of the network topology.\n\nStructu
 red networks\, on the other hand\, tend to have good mixing properties\, a
 nd de Bruijn networks can be shown to achieve optimal mixing and therefore
  make an ideal candidate for anonymous p2p networks. We study the approxim
 ations to de Bruijn networks used in several p2p systems and show that the
 y provide good anonymity on average\, and acceptable anonymity in the wors
 t case\, even when the full topology of the network is known to the attack
 ers. 
LOCATION:Lecture Theatre 2\, Computer Laboratory\, William Gates Building
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