Tor (réseau)

Résumé

Tor est un réseau informatique superposé mondial et décentralisé. Il se compose de serveurs, appelés nœuds du réseau et dont la liste est publique. Ce réseau permet d'anonymiser l'origine de connexions TCP. Cela peut entre autres servir à anonymiser la source d'une session de navigation Web ou de messagerie instantanée. Cependant, l'anonymisation du flux n'est pas totale, car l'application peut transmettre des informations annexes permettant d'identifier la personne, c'est pourquoi le projet Tor développe également un navigateur Web fondé sur Firefox, Tor Browser, ainsi que d'autres applications spécialement modifiées pour préserver l'anonymat de leurs usagers. L'implémentation de référence du protocole s'appelle « tor », c'est un logiciel libre sous licence BSD révisée. Le projet Tor reçoit le prix du logiciel libre 2010, dans la catégorie « projet d’intérêt social ». Le nom « Tor » est à l’origine un acronyme pour « The Onion Router », littéralement « le routeur oignon », qui s’est

Source officielle

https://fr.wikipedia.org/wiki/Tor_(r%C3%A9seau)

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Cours associés (8)

This is an introductory course to computer security and privacy. Its goal is to provide students with means to reason about security and privacy problems, and provide them with tools to confront them.

A decentralized system is one that works when no single party is in charge or fully trusted. This course teaches decentralized systems principles while guiding students through the development and testing of their own decentralized system incorporating messaging, encryption, and blockchain concepts.

This course will offer students a broad but hands-on introduction to technologies of human self-organization.

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Séances de cours associées (15)

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Current anonymous communication systems make a trade-off between weak anonymity among many nodes, via onion routing, and strong anonymity among few nodes, via DC-nets. We develop novel techniques in Dissent, a practical group anonymity system, to increase by over two orders of magnitude the scalability of strong, traffic analysis resistant approaches. Dissent derives its scalability from a client/server architecture, in which many unreliable clients depend on a smaller and more robust, but administratively decentralized, set of servers. Clients trust only that at least one server in the set is honest, but need not know or choose which server to trust. Unlike the quadratic costs of prior peer-to-peer DC-nets schemes, Dissent's client/server design makes communication and processing costs linear in the number of clients, and hence in anonymity set size. Further, Dissent's servers can unilaterally ensure progress, even if clients respond slowly or disconnect at arbitrary times, ensuring robustness against client churn, tail latencies, and DoS attacks. On DeterLab, Dissent scales to 5,000 online participants with latencies as low as 600 milliseconds for 600-client groups. An anonymous Web browsing application also shows that Dissent's performance suffices for interactive communication within smaller local-area groups.

2012

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Proactively Accountable Anonymous Messaging in Verdict

Henry Nathaniel Corrigan-Gibbs, Bryan Alexander Ford

Among anonymity systems, DC-nets have long held attraction for their resistance to traffic analysis attacks, but practical implementations remain vulnerable to internal disruption or “jamming” attacks, which require time-consuming detection procedures to resolve. We present Verdict, the first practical anonymous group communication system built using proactively verifiable DC-nets: participants use public-key cryptography to construct DC-net ciphertexts, and use zero-knowledge proofs of knowledge to detect and exclude misbehavior before disruption. We compare three alternative constructions for verifiable DC-nets: one using bilinear maps and two based on simpler ElGamal encryption. While verifiable DC-nets incur higher computational overheads due to the public-key cryptography involved, our experiments suggest that Verdict is practical for anonymous group messaging or microblogging applications, supporting groups of 100 clients at 1 second per round or 1000 clients at 10 seconds per round. Furthermore, we show how existing symmetric-key DC-nets can “fall back” to a verifiable DC-net to quickly identify misbehavior, speeding up previous detections schemes by two orders of magnitude.

2013

Chargement

MorphIT: Morphing Packet Reports for Internet Transparency

Bryan Alexander Ford, Georgia Fragkouli

Can we improve Internet transparency without worsening user anonymity? For a long time, researchers have been proposing transparency systems, where traffic reports produced at strategic network points help assess network behavior and verify service-level agreements or neutrality compliance. However, such reports necessarily reveal when certain traffic appeared at a certain network point, and this information could, in principle, be used to compromise low-latency anonymity networks like Tor. In this paper, we examine whether more Internet transparency necessarily means less anonymity. We start from the information that a basic transparency solution would publish about a network and study how that would impact the anonymity of the network’s users. Then we study how to change, in real time, the time granularity of traffic reports in order to preserve both user anonymity and report utility. We evaluate with real and synthetic data and show that our algorithm can offer a good anonymity/utility balance, even in adversarial scenarios where aggregates consist of very few flows.

Sciendo2019

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