Papers by Mema Roussopoulos
Digital repositories, either digital preservation systems or archival systems, periodically check... more Digital repositories, either digital preservation systems or archival systems, periodically check the integrity of stored objects to assure users of their correctness. To do so, prior solutions calculate integrity metadata and require the repository to store it alongside the actual data objects. This integrity metadata is essential for regularly verifying the correctness of the stored data objects. To safeguard and detect damage to this metadata, prior solutions rely on widely visible media, that is unaffiliated third parties, to store and provide back digests of the metadata to verify it is intact. However, they do not address recovery of the integrity metadata in case of damage or attack by an adversary. In essence, they do not preserve this metadata. We introduce IntegrityCatalog, a system that collects all integrity related metadata in a single component, and treats them as first class objects, managing both their integrity and their preservation. We introduce a treap-based persistent authenticated dictionary managing arbitrary length key/value pairs, which we use to store all integrity metadata, accessible simply by object name. Additionally, IntegrityCatalog is a distributed system that includes a network protocol that manages both corruption detection and preservation of this metadata, using administrator-selected network peers with two possible roles. Verifiers store and offer attestations on digests and have minimal storage requirements, while preservers efficiently synchronize a complete copy of the catalog to assist in recovery in case of a detected catalog compromise on the local system. We describe our prototype implementation of IntegrityCatalog, measure its performance empirically, and demonstrate its effectiveness in real-world situations, with worst measured throughput of approximately 1K insertions per second, and 2K verified search operations per second.
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Journal of Systems and Software, 2015
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Lecture Notes in Computer Science, 2012
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Eprint Arxiv Cs 0411078, 2004
The design of the defenses Internet systems can deploy against attack, especially adaptive and re... more The design of the defenses Internet systems can deploy against attack, especially adaptive and resilient defenses, must start from a realistic model of the threat. This requires an assessment of the capabilities of the adversary. The design typically evolves through a process of simulating both the system and the adversary. This requires the design and implementation of a simulated adversary based on the capability assessment. Consensus on the capabilities of a suitable adversary is not evident. Part of the recent redesign of the protocol used by peers in the LOCKSS digital preservation system included a conservative assessment of the adversary's capabilities. We present our assessment and the implications we drew from it as a step towards a reusable adversary specification.
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Computing Research Repository, 2002
Recently the problem of indexing and locating content in peer-to-peer networks has received much ... more Recently the problem of indexing and locating content in peer-to-peer networks has received much attention. Previous work suggests caching index entries at intermediate nodes that lie on the paths taken by search queries, but until now there has been little focus on how to maintain these intermediate caches. This paper proposes CUP, a new comprehensive architecture for Controlled Update Propagation
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The emergence of sensor networks and distributed applications that gen- erate data streams has cr... more The emergence of sensor networks and distributed applications that gen- erate data streams has created a need for Internet overlays designed for streaming data. Such stream-based overlay network (SBONs) consist of a set of Internet hosts that collect, process, and deliver stream-based data to multiple applications. A key challenge in the design and im- plementation of SBONs is efficient path
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Networked Systems Design and Implementation, 2007
Blogs and RSS feeds are becoming increasingly popular. The blogging site LiveJournal has over 11 ... more Blogs and RSS feeds are becoming increasingly popular. The blogging site LiveJournal has over 11 million user accounts, and according to one report, over 1.6 million postings are made to blogs every day. The "Blogosphere" is a new hotbed of Internet-based media that represents a shift from mostly static content to dynamic, continuously-updated discussions. The problem is that finding and
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In the hope of stimulating discussion, we present a heuristic decision tree that designers can us... more In the hope of stimulating discussion, we present a heuristic decision tree that designers can use to judge how suitable a P2P solution might be for a particular problem. It is based on characteristics of a wide range of P2P systems from the literature, both proposed and deployed. These include budget, resource relevance, trust, rate of system change, and criticality.
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IEEE INFOCOM 2008 - The 27th Conference on Computer Communications, 2008
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2014 IEEE/ACM 7th International Conference on Utility and Cloud Computing, 2014
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Mobile Computing and Communications Review, 1996
People are the outsiders in the current communications revolution. Computer hosts, pager terminal... more People are the outsiders in the current communications revolution. Computer hosts, pager terminals, and telephones are addressable entities throughout the Internet and telephony systems. Human beings, however, still need application-specic tricks to be identied, like email addresses, telephone numbers, and ICQ IDs. The key challenge today is to nd people and communicate with them personally, as opposed to communicating merely
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Papers by Mema Roussopoulos