3 research outputs found
Efficient Peer-To-Peer Lookup Based on a Distributed Trie
Two main approaches have been taken for distributed key/value lookup operations in peer-to-peer systems: broadcast searches [1, 2] and location-deterministic algorithms [5, 6, 7, 9]. We describe a third alternative based on a distributed trie. This algorithm functions well in a very dynamic, hostile environment, offering security benefits over prior proposals. Our approach takes advantage of working-set temporal locality and global key/value distribution skews due to content popularity. Peers gradually learn system state during lookups, receiving the sought values and/or internal information used by the trie. The distributed trie converges to an accurate network map over time. We describe several modes of information piggybacking, and conservative and liberal variants of the basic algorithm for adversarial settings. Simulations show efficient lookups and low failure rates
Private and censorship-resistant communication over public networks
Society’s increasing reliance on digital communication networks is creating unprecedented opportunities for wholesale
surveillance and censorship. This thesis investigates the use of public networks such as the Internet to build
robust, private communication systems that can resist monitoring and attacks by powerful adversaries such as national
governments.
We sketch the design of a censorship-resistant communication system based on peer-to-peer Internet overlays in which
the participants only communicate directly with people they know and trust. This ‘friend-to-friend’ approach protects
the participants’ privacy, but it also presents two significant challenges. The first is that, as with any peer-to-peer
overlay, the users of the system must collectively provide the resources necessary for its operation; some users might
prefer to use the system without contributing resources equal to those they consume, and if many users do so, the
system may not be able to survive.
To address this challenge we present a new game theoretic model of the problem of encouraging cooperation between
selfish actors under conditions of scarcity, and develop a strategy for the game that provides rational incentives for
cooperation under a wide range of conditions.
The second challenge is that the structure of a friend-to-friend overlay may reveal the users’ social relationships to
an adversary monitoring the underlying network. To conceal their sensitive relationships from the adversary, the
users must be able to communicate indirectly across the overlay in a way that resists monitoring and attacks by other
participants.
We address this second challenge by developing two new routing protocols that robustly deliver messages across
networks with unknown topologies, without revealing the identities of the communication endpoints to intermediate
nodes or vice versa. The protocols make use of a novel unforgeable acknowledgement mechanism that proves that a
message has been delivered without identifying the source or destination of the message or the path by which it was
delivered. One of the routing protocols is shown to be robust to attacks by malicious participants, while the other
provides rational incentives for selfish participants to cooperate in forwarding messages