Browsing by Author "Marsh, Michael A."
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Item Efficient Lookup on Unstructured Topologies(2006-03-02T17:22:28Z) Morselli, Ruggero; Bhattacharjee, Bobby; Marsh, Michael A.; Srinivasan, AravindWe present LMS, a protocol for efficient lookup on unstructured networks. Our protocol uses a virtual namespace without imposing specific topologies. It is more efficient than existing lookup protocols for unstructured networks, and thus is an attractive alternative for applications in which the topology cannot be structured as a Distributed Hash Table (DHT). We present analytic bounds for the worst-case performance of our protocol. Through detailed simulations (with up to 100,000 nodes), we show that the actual performance on realistic topologies is significantly better. We also show in both simulations and a complete implementation (which includes over five hundred nodes) that our protocol is inherently robust against multiple node failures and can adapt its replication strategy to optimize searches according to a specific heuristic. Moreover, the simulation demonstrates the resilience of LMS to high node turnover rates, and that it can easily adapt to orders of magnitude changes in network size. The overhead incurred by LMS is small, and its performance approaches that of DHTs on networks of similar size.Item KeyChains: A Decentralized Public-Key Infrastructure(2006-03-02T18:59:57Z) Morselli, Ruggero; Bhattacharjee, Bobby; Katz, Jonathan; Marsh, Michael A.A Certification Authority (CA) can be used to certify keys and build a public-key infrastructure (PKI) when all users trust the same CA. A decentralized PKI trades off absolute assurance on keys for independence from central control and improved scalability and robustness. The PGP ``web of trust'' model has been suggested as a decentralized certification system, and has been used with great success for secure email. Although the PGP web of trust model allows anyone to issue certificates which can be used to form certificate chains, the discovery and construction of certificate chains relies on centralized keyservers to store certificates and respond to queries. In this paper, we design and implement KeyChains, a peer-to-peer system which incorporates a novel lookup mechanism specifically tailored to the task of generating and retrieving certificate chains in completely unstructured networks. By layering our system on top of the web of trust model, we thus obtain the first PKI which is truly decentralized in all respects. Our analysis and simulations show that the resulting system is both efficient and secure.