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Anonymity and Censorship Resistance in Unstructured Overlay Networks*
Michael Backes4, Marek Hamerlik1, Alessandro Linari2, Matteo Maffei1, Christos Tryfonopoulos3, and Gerhard Weikum3
1Saarland University
mhamerli@cs.uni-sb.de
maffei@cs.uni-sb.de
2Oxford Brookes University & Nominet UK
alessandro@nominet.org.uk
3Max Planck Institut für Informatik
trifon@mpi-inf.mpg.de
weikum@mpi-inf.mpg.de
4Saarland University & MPI-SWS
backes@cs.uni-sb.de
Abstract. This paper presents Clouds, a peer-to-peer protocol that guarantees both anonymity and censorship resistance in semantic overlay networks. The design of such a protocol needs to meet a number of challenging goals: enabling the exchange of encrypted messages without assuming previously shared secrets, avoiding centralised infrastructures, like trusted servers or gateways, and guaranteeing efficiency without establishing direct connections between peers. Anonymity is achieved by cloaking the identity of protocol participants behind groups of semantically close peers. Censorship resistance is guaranteed by a cryptographic protocol securing the anonymous communication between the querying peer and the resource provider. Although we instantiate our technique on semantic overlay networks to exploit their retrieval capabilities, our framework is general and can be applied to any unstructured overlay network. Experimental results demonstrate the security properties of Clouds under different attacks and show the message overhead and retrieval effectiveness of the protocol.
*Work partially supported by the initiative for excellence and by Emmy Noether program of the German federal government and by Miur project SOFT: “Security Oriented Formal Techniques”.
LNCS 5870, p. 147 ff.
lncs@springer.com
© Springer-Verlag Berlin Heidelberg 2009