Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Towards an Analysis of Onion RoutingP. Syverson, G. Tsudik, M. Reed, C. Landwehrcs6461Computer Science, MTUByung ChoiIntroduction●Primary goal of onion routing: strongly private communication in real time over a public network at reasonable cost and efficiency●NRL implementation supports 1.5 M connections per month as of 2000●Second generation under way●Onion Routing UsageOnion routing overview●COR: Core Onion Router designed to pass information in real time, limiting mixing.●Proxy-aware applications–HTTP, FTP, SMTP, ...●Proxy–Application specific privacy filter–Application specific translator–Onion management layer–Proxy must know the topology and entry and exit policies!Overview●Longstanding TCP connections, thick pipes, anonymous connections, clique!●Stream ciphers at each onion router●128 bytes cell●Cell changes its appearance but not size, from input to putput●Email, Web transactions, short lived, attack resistant●Long lived? - FTP, SSH, ... attack susceptibleSecurity goals●Sender activity●Receiver activity●Sender content●Receiver content●Source destination linkingNetwork model●The network of onion routers is a clique, fully connected●Bandwidth limited to a constant rate●Exit policy at each node unrestricted●For each route, each hop is chosen randomly●The number of nodes in a route 2 – infinitive with r onion routers–Remote-COR configuration–Local-COR configurationNetwork model●Entrance policy via remote-COR unrestricted●Entrance policy via local-COR is to exclude all but internal connectionsAdversary model●Observer●Disrupter●Hostile user●Compromised COR–Single adversary–Multiple adversary–Roving adversary–Global adversarySecurity assessment●Roving adversary–Round?–Automatic
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