Lukasz Opyrchal

Exploiting IP multicast in content-based publish-subscribe systems

Publish-subscribe systems are evolving toward using content-based subscription rather than subject-based subscription. A key problem in implementing such systems is that a straightforward mapping from matching sets to multicast groups produces a number of groups that rapidly grows beyond practical limits. This paper proposes a set of alternative algorithms for solving this problem, by: (1) using a smaller set of overbroad multicast groups, judiciously chosen to minimize imprecision; (2) issuing multiple multicasts to appropriately chosen clusters; or (3) sending an event over multiple hops each involving a multicast to a set of neighbors. We evaluate these algorithms on a simulated wide-area network. We find that (1) a simple flooding algorithm is viable over an extensive range of conditions; and (2) under conditions of high selectivity and high regionalism of subscriptions, the other approaches mentioned above perform significantly better; however, the specific algorithm to use depends upon the economics of deployment.

Efficient object serialization in Java

Object serialization is the ability of an object to write a complete state of itself and of any objects that it references to an output stream, so that it can be recreated from the serialized representation at a later time. Pickling, the process of creating a serialized representation of objects, has been investigated for many years in the context of many different distributed systems. Sun Microsystems introduced a simple and extendible API for object serialization in version 1.1 of the Java Development Kit. Application developers can use this standard serialization in their applications, or they can develop custom versions for different user-defined classes. Many distributed applications that use standard serialization to communicate between distributed nodes, experience significant degradation in performance due to large sites of serialized objects. We present a number of improvements to the serialization mechanism aimed at decreasing pickle sizes without visible degradation in serialization performance. Through performance results, we show that it produces pickles up to 50% smaller without degrading serialization performance.

Supporting Privacy Policies in a Publish-Subscribe Substrate for Pervasive Environments

A location tracking sensor network is being deployed in several buildings at the University of Michigan to help explore issues in design of pervasive environments. Managing privacy is expected to be a significant concern for acceptance of such pervasive environments. This paper outlines an initial design of a publish-subscribe communication substrate for controlled distribution of sensor data. We describe our prototype as well as a privacy-aware location tracking application built on top of the system. The focus of this paper is on policy management. We provide users with the means to control distribution of data about them (such as their location information) through the use of privacy policies. The paper shows how a wide variety of policies can be specified in the system and points out directions for future work.

Designing a Publish-Subscribe Substrate for Privacy/Security in Pervasive Environments

The emergence of a multitude of technologies for tracking locations is leading to the design of pervasive location-tracking environments. Managing privacy is expected to be a significant concern for acceptance of such pervasive environments. This paper outlines an initial design of a publish-subscribe communication substrate for controlled distribution of sensor data. We describe our prototype as well as a privacy-aware location-tracking application built on top of the system. The focus of this paper is on policy management so as to provide means for allowing users to control distribution of data tagged with their ID to other users and services

Fighting Phishing with Trusted Email

Phishing is the combination of social engineering and technical exploits designed to convince a victim to provide personal information, usually for the monetary gain of the attacker (phisher). Attempts to stop phishing by preventing a user from interacting with a malicious web site have shown to be ineffective. We introduce a method to aid in the prevention of phishing by combining automatic and transparent email signing with an email client plugin. The plugin can detect unsigned spoofed messages. In this manner, the user is prevented (or at least discouraged) from visiting malicious web sites, thus stopping the data-gathering phase of the phishing attack before it begins. We describe the system, implementation, weaknesses, and our ongoing user experiments.

PBS: Private Bartering Systems

Barter trade is a growing part of the world economy. Hundreds of thousands of companies in the US alone participate in barter. Barter is also used in other domains, such as resource management in distributed systems. Existing algorithms for finding barter trades require that values of goods are publicly known (whether they are set by a global function or individual utility functions for each user). The fact that each user must reveal her utility function in order to find barter trades is a potential disincentive to using bartering. We present a first step in the creation of a privacy-preserving bartering system. We present algorithms and privacy-preserving protocols in the honest but curious model for determining the existence of win-win trades (and algorithms and protocols for finding such trades). We discuss a number of remaining open problems and extensions for future work.

All proxy scheme for event source anonymity in wireless sensor networks

Event source anonymity is potentially an important aspect of secure wireless sensor networks (WSN). The existing schemes developed for wired networks do not work in WSNs due to the characteristics of radio transmission and limited resources. A recent article proposed several solutions for the strong global adversary model [1]. The protocols depend on dummy messages and special proxy nodes that filter out unnecessary messages. We present an improved scheme - the All Proxy Scheme - that improves the efficiency by performing message filtering at every sensor node. Our simulations show that APS improves real message delivery ratio and decreases message overhead while maintaining the same security guarantees as PFS and TFS described in [1].

Publish Subscribe Middleware

Publish subscribe (pub-sub) middleware has become very popular in building large scale distributed systems. Application domains that benefit from publish subscribe architectures include supply-chain management, financial applications, e-commerce applications, workflow systems, and information distribution systems.

Large‐Scale Group Collaboration Systems

This article focuses on current and emerging distributed platforms that support large-scale collaboration. These platforms include centralized web-based systems as well as distributed peer-to-peer applications. We describe different technologies used to build large-scale systems, the trade-offs each technology makes, and some existing systems. The rest of this article is organized as follows: The section “Types of Architectures” describes different types of distributed systems and how each can be used to build large scale collaborative environments. “Overview of Existing Systems” describes several existing systems with collaborative features. Finally, the conclusion summarizes the article and presents a look at possible future of collaborative systems. Keywords: collaboration; Facebook; MySpace; text messages; publish-subscribe systems; peer-to-peer systems; instant messaging; file sharing

Enhancing undergraduate computer science education through a university-wide summer research program

Recruiting undergraduates for research projects and managing these projects to ensure success presents numerous challenges; however, undergraduate student involvement in research provides many opportunities for students to strengthen their studies in computer science. One unique and successful program that involves undergraduates in research is Miami Universitys Undergraduate Summer Scholars (USS) program. This competitive program provides 100 awards every summer to selected student/faculty pairs to pursue original research projects. The student recipient works full time (40 hours per week) for a 10-week period with the faculty mentor and receives a stipend of