Category Archives: Acadia seminar series

04/02/2020 – Talk by Vasileios Drakopoulos

Title: BIVARIATE FRACTAL INTERPOLATION SURFACES: THEORY AND APPLICATIONS
Time: 14:15
Location: Meeting Room B, Building Zeta
Speaker: Vasileios Drakopoulos
Abstract: Fractal interpolation offers an alternative to traditional interpolation techniques, aiming primarily at data which present detail at different scales or some degree of self-similarity. These characteristics, often intrinsic in natural objects, imply an irregular and non-smooth structure which is inconvenient to capture by elementary functions such as polynomials. 
Specifically, a fractal interpolation function, as defined by M. F. Barnsley and other researchers, can be considered as a continuous function whose graph is the attractor of an appropriately chosen iterated function system. If this graph, usually of non-integral dimension, belongs to the three-dimensional space and has Hausdorff – Besicovitch dimension between 2 and 3, then the resulting attractor is called fractal interpolation surface. 
During this talk, we discuss the theory and applications of fractal interpolation surfaces constructed by bivariate functions on rectangular grids. As far as the theory is concerned, we focus on two important issues: (a) The ensurance of continuity, which is in general a more complicated task than in the case of fractal interpolation functions on the plane, and (b) the identification of the vertical scaling factors which are the only free parameters in such a construction. As far as the applied part is concerned, we present several practical applications of fractal interpolation surfaces, including image compression, 3D data representation and medical imaging.

27/11/2019 – Talk by Carey Lee Williamson

Title: An Empirical Study of Campus-Level Instagram Traffic
Time: 13:00
Location: Meeting Room B, Building Zeta
Speaker: Carey Lee Williamson
Abstract: Instagram is a popular network application for photo sharing, video streaming, and online social media interaction. This talk presents results from an empirical study of Instagram network traffic, as viewed from a large campus edge network. Despite the challenges of NAT, DHCP, end-to-end encryption, and high traffic volume, we are able to identify key characteristics of Instagram traffic, which exceeds 1 TB per day. The main highlights from our study include classic observations such as diurnal usage patterns, Zipf-like distributions for IP frequency-rank profile, and heavy-tailed transfer size distributions. Several new observations include anomalous spikes in Instagram traffic, some network policies that inhibit Instagram usage, and some small differences in Instagram usage between campus-based users and the general public.

18/11/2019 – Talk by Benjamin Krumnow

Title: mashing OpenWPM for fun and profit
Time: 10:00
Location: Acadia Lab, Building Zeta
Type: Research talk
Speaker:  Hugo Jonker
Abstract: Web bots are a widely recognized tool to conduct empirical studies in the World Wide Web. OpenWPM is a framework that uses a web bot framework to facilitates web measurements. It is used in at least 46 scientific studies. However, there are clear indications that web sites attempt to recognize web bots and thereupon serve deviating content or block bots. Due to browser fingerprinting, this can already happen with the first call of a web page. For doing so, a web server attempts to retrieve unique properties that distinguish a web bot from human-controlled web browsers. To what extent OpenWPM is vulnerable to fingerprint-based detection has yet not been questioned. In this talk, I will present our investigation of detecting OpenWPM users based on their fingerprints. For that, we conduct a systematic analysis of the OpenWPM system architecture. We determine unique properties in OpenWPM’s fingerprint by applying fingerprinting and template attack tools for each component of OpenWPM. Our study reveals over 2K not-yet known properties, that would allow any web server to detect OpenWPM users. We show that most differences in OpenWPM result from automation components or the Firefox headless mode. Nevertheless, some deviations only occur in OpenWPM and could also be used to distinguish OpenWPM from ordinary bots. For demonstration purposes, we develop a web application that detects OpenWPM-based web clients and delivers manipulated content to them.

18/11/2019 – Talk by Hugo Jonker

Title: Shepherd – an automatic and large-scale study of website login security
Time: 9:30
Location: Acadia Lab, Building Zeta
Type: Research talk
Speaker:  Hugo Jonker
Abstract: Logging in on websites is common. However, it wasn’t always secure – as FireSheep showed dramatically in 2010. A malicious agent could simply eavesdrop on WiFi traffic and steal credentials of logged-in users. In response to FireSheep, major websites fixed their login security. However, it remains unclear whether others followed suit.Investigating this scientifically is fraught with challenges: acquiring passwords, automating logins on unknown websites, etc. In this talk, we present Shepherd, the result of a 2 year engineering effort to automate website logins. Moreover, we will present and discuss the results of a security scan with Shepherd, which showed that out of 7,113 sites where login was successful, 2,417 (34%) is still vulnerable to some variant on the FireSheep attack.

28/10/2019 – Talk by Silvia Crafa

Title: Smart contracts programming: formal methods in action
Time: 9:30
Location: Meeting Room B, Building Zeta
Type: Research talk
Speaker:  Silvia Crafa
Abstract:
In this talk I’ll focus on smart contracts in the Ethereum blockchain, discussing their motivations and  presenting their programming model. I’ll show how the theory of programming languages can be used in this new context to clarify the semantics of contracts written in the Solidity programming language. Moreover, I’ll show how the development of the type theory of the formalised core of Solidity revealed a type-safety issue in its compiler, and I’ll suggest a solution that might be reused in the more classical context of Object Oriented Languages.

19/09/2019 – Talk by Shantanu Das

Title: Patrolling on Dynamic Ring Networks
Time: 15:50
Location: Acadia Lab, Building Zeta
Type: Research talk
Speaker:  Shantanu Das
Abstract: 
We study the problem of patrolling the nodes of a network collaboratively by a team of mobile agents, such that each node of the network is visited by at least one agent once in every I(n) time units, with the objective of minimizing the idle time I(n). While patrolling has  been studied previously for static networks, we investigate the problem on dynamic networks with a fixed set of nodes, but dynamic edges. In particular, we consider 1-interval-connected ring networks and provide various patrolling algorithms for such networks, for k = 2 or k > 2 agents.  We also show almost matching lower bounds that hold even for the best starting configurations. Thus, our algorithms achieve close to optimal idle time. Further, we show a clear separation in terms of idle time, for agents that have prior knowledge of the dynamic networks compared to agents that do not have such knowledge. This paper provides the first known results for collaborative patrolling on dynamic graphs.

13/12/2018 – Talk by Shantanu Das

Title: Exploration Algorithms for Energy Constrained Robots
Time: 13:00
Location: Meeting Room B, Building Zeta
Type: Research talk
Speaker:  Shantanu Das
Abstract: 
We consider a team of mobile robots moving on graph where each robot has a constraint on its energy consumption which limits the number of edges it can traverse. Under this constraint we look at the problem of graph exploration. Since any single robot may not completely explore the graph, the robots need to collaborate so that each node is visited by some robot. We consider three different optimization criteria: the size of the team, the energy budget per robot, and finally the number of nodes visited. We present efficient algorithms and prove lower bounds on these different measures of optimization. We also show a separation result between exploration with return and exploration without return.

30/11/2018 – Talk by Manali Chakraborty

Title: An Intelligent Framework for Managing Smart Power Grid
Time: 12:00
Location: Meeting Room B, Building Zeta
Type: Research talk
Speaker:  An Intelligent Framework for Managing Smart Power Grid
Abstract: 
The increasing dependability on the communication network makes Smart Grid vulnerable towards several cyber security threats. Advanced metering infrastructure (AMI) is arguably the most important and critical part of Smart Grid. AMI deals with the most sensitive information in the Grid and transmits them through the network. There already exist a good number of security solutions for AMI. However the percentage of security attacks is also increasing day by day and so does the innovative and intelligent ideas behind those attacks. As the inherent characteristics of Smart Grid is quite unique and different from traditional IT networks, the existing solutions fall short to handle these Smart Grid specific problems. Besides, balancing the supply-demand ratio in the Smart Grid considering all these odds, is far from being an easy job and requires additional technological support. Moreover, in order to maximize the benefits of Smart Grid, it is utmost important to connect and manage all the components and devices in the grid. This work in this thesis focuses on the feasibility of improving the security and autonomic functionalities of Advance Metering Infrastructure (AMI) in Smart Grid. The work can be broadly categorized into three parts depending on the concerned functionality of AMI.

23/11/2018 – Talk by Leonardo Maccari

Title: Community Networks, a theme for networking research
Time: 13:00
Location: Meeting Room A, Building Zeta
Type: Research talk
Speaker:  Leonardo Maccari
Abstract: 
In the last few years, thanks to a series of European research projects, the scientific interest in community networks (CNs) raised considerably.
A CN is a wireless mesh network built by a community of people that grows in an unplanned way when the community enlarges.
Due to the improved performance of wireless standards, today we have mesh networks made of hundreds of nodes, or even thousands of nodes, and many stakeholders consider them a key instrument to reduce digital divide (50% of the world population was still disconnected in 2017).
CNs are also a stimulating playground for networking research to be applied to other fields. As an example, in this talk I will describe one of the challenges we tackled, which is the scalability of routing protocols.
The solution we proposed exploits the concept of betweenness centrality to fine-tune routing protocols in an automated and back-compatible way.
While we designed, tested and implemented it in CNs, we also extended the concept to other kinds of networks. Specifically, we are now considering how to apply the same principle to Internet routing, in order improve the convergence of the BGP protocol. In the process, we formalized the first fully distributed exact algorithm for centrality computation on a generic graph, which is needed to compute centrality when the full network graph is unknown. We can now study centrality-based optimizations on BGP but also in other application domains, like sensor networks.
I will conclude with a future step of this research, which is a data-based approach to generate realistic network topologies using several communication technologies. The final goal is to characterize the high level features of the network graph (cost, population coverage, robustness etc.) in order to take informed decisions on the choice of the best technology for a specific context.

The talk is based on the following publications:

1) Leonardo Maccari, Renato Lo Cigno. “Pop-routing: Centrality-based tuning of control messages for faster route convergence”. Proceedings of the International Conference on Computer Communications (INFOCOM), April 2016.
2) Leonardo Maccari, Renato Lo Cigno, “Improving Routing Convergence with Centrality: Theory and Implementation of Pop-Routing”. IEEE Transactions on Networking, vol. 26, pp. 2216–2229, Oct. 2018
3) Leonardo Maccari, Lorenzo Ghiro, Alessio Guerrieri, Alberto Montresor, Renato Lo Cigno, “On the Distributed Computation of Load Centrality and Its Application to DV Routing”. Proceedings of the International Conference on Computer Communications (INFOCOM), April 2018.