Anonymous and censorship resistant content sharing in unstructured overlays

Abstract

Semantic overlay networks are an instance of unstructured overlays, where System OverviewSemantic Overlay Networks (SONs) have proven a useful technology not only for distributed information retrieval, but also as a natural distributed alternative to Web 2.0 application domains such as decentralized social networking in the spirit of Flickr or del.icio.us. In this work we present Clouds, a novel system that provides anonymity and censorship resistance over SONs. Anonymity is achieved by relying on a self-organization of peers into groups that we call clouds. Message routing takes place among clouds instead of peers, thus hiding the identity of both the resource provider and the querying peer, while cloud size is a tunable parameter that affects anonymity and efficiency. Censorship resistance at communication level is achieved by a cryptographic protocol that guarantees the secrecy of the resource, thus avoiding censorship based on the inspection of the messages circulating in the network. The design of such a protocol needs to meet a number of challenging goals: allowing for the exchange of encrypted messages without assuming previously shared secrets, avoiding centralized infrastructures, like trusted servers or static gateways (e.g., as in [2]), and guaranteeing efficiency without establishing direct connections between peers. Clouds is the first system to guarantee anonymity and censorship resistance in SONs by addressing the aforementioned challenges.Anonymity in Clouds is achieved by cloaking both the querying peer and the resource provider behind a group of neighboring peers, called cloud. Peers generate clouds at random, without necessarily using them, to minimize the correlation between the events of joining and using a cloud. They also non-deterministically Copyright is held by the author/owner(s). PODC'08, August 18-21, 2008, Toronto, Ontario, Canada. ACM 978-1-59593-989-0/08/08. Figure 1. Overview of Clouds protocol.decide to participate or not in clouds created by other peers. By design, clouds are populated by peers in the neighborhood of the cloud initiator. Communication takes place between clouds, and all peers in a cloud share the same probability of being involved in any communication which has this cloud as the start-or endpoint (k-anonymity). Clouds protocol is designed so that the observable behavior is the same for all peers, regardless of initiating of forwarding a message, to avoid compromising anonymity. The proposed cryptographic protocol aims at addressing the problem of censorship at the communication level, where a malicious party aims at filtering out any communication (i.e., query or resource) that contains unwanted content. The privacy of the resource is protected by cryptography, making it hard for the attacker to censor the communication by inspecting the message content.The protocol is composed of four steps summarized in Figure 1. A querying peer P uses a cloud C P it participates in to issue a query q. This query follows a random walk in the cloud to obscure the me...

STeP-Archival: Storage Integrity and Tamper Resistance Using Data Entanglement

“…State of the Art 1) Censorship-Resistant File Sharing: Censorship-resistant file sharing systems and overlays have been studied in various forms and for a large number of settings and applications, starting with the Eternity Service proposal [1]. This was followed by Publius [2], Freenet [3], Free Haven [4], Dagster [5], Tangler [6], SiRiUS [7], Tahoe [8], and Clouds [9]. All these solutions are summarized and put in context in a recent survey on privacy and decentralization [10].…”

Invisible Barriers: Identifying restrictions affecting New Zealanders' access to the Internet

“…All of these systems allow the user to be connected to one proxy outside the territory of censorship in order to gain the desired content. There are other approaches to circumvent censorship such as semantic overlay network [67]. Backes et al [67] have used clouds in order to provide anonymity instead of using peers.…”

“…There are other approaches to circumvent censorship such as semantic overlay network [67]. Backes et al [67] have used clouds in order to provide anonymity instead of using peers.…”