Spiridon Bakiras

Spiridon Bakiras
Hamad bin Khalifa University | HBKU

About

64
Publications
11,101
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
1,554
Citations

Publications

Publications (64)
Article
Full-text available
A plethora of contact tracing apps have been developed and deployed in several countries around the world in the battle against COVID-19. However, people are rightfully concerned about the security and privacy risks of such applications. To address these issues, in this paper we provide two main contributions. First, we present an in-depth analysis...
Chapter
Fake news is a serious concern that has received a lot of attention lately due to its harmful impact on society. In order to limit the spread of fake news, researchers have proposed automated ways to identify fake news articles using artificial intelligence and neural network models. However, existing methods do not achieve a high level of accuracy...
Article
In this article, we introduce I Control My Space (ICMS), a novel, fine-grained, and flexible system that allows space owners to define and enforce access restriction and service policies on mobile devices at their premises. This is achieved by enforcing restrictions on the use of applications and even specific permissions on the mobile device (e....
Article
Full-text available
This paper presents a privacy persevering framework for a decentralized stock exchange platform, ensuring anonymity and unlinkability of the investors’ accounts and their respective trading activities. The proposed framework meets these privacy requirements by (i) anonymizing both the unique account identifier (NIN) and balance information through...
Preprint
Full-text available
Contact tracing with mobile applications is an attractive approach for many governments and industry initiatives to address the Covid-19 pandemic. However, many approaches today have severe privacy and security issues, and many of them also fail to offer a sustainable contact tracing infrastructure due to the demanding energy consumption. This work...
Article
Full-text available
Contact tracing is the techno-choice of reference to address the COVID-19 pandemic. Many of the current approaches have severe privacy and security issues and fail to offer a sustainable contact tracing infrastructure. We address these issues introducing an innovative, privacy-preserving, sustainable, and experimentally tested architecture that lev...
Article
Full-text available
Video surveillance on a massive scale can be a vital tool for law enforcement agencies. To mitigate the serious privacy concerns of wide-scale video surveillance, researchers have designed secure and privacy-preserving protocols that obliviously match live feeds against a suspects’ database. However, existing approaches are very expensive in terms...
Article
An energy trading system is essential for the successful integration of Electric Vehicles (EVs) into the smart grid. In this paper, leveraging blockchain technology, we first propose a privacy-preserving charging-station-to-vehicle (CS2V) energy trading scheme. The CS2V scheme is useful in crowded cities where there is a need for a charging infrast...
Article
Full-text available
Intelligent transportation systems necessitate a fine-grained and accurate estimation of vehicular traffic flows across critical paths of the underlying road network. However, such statistics should be collected in a manner that does not disclose the trajectories of individual users. To this end, we introduce a privacy-preserving protocol that leve...
Article
Full-text available
Digital twinning is one of the top ten technology trends in the last couple of years, due to its high applicability in the industrial sector. The integration of big data analytics and artificial intelligence/machine learning (AI-ML) techniques with digital twinning, further enriches its significance and research potential with new opportunities and...
Preprint
Full-text available
Contact tracing via mobile applications is gaining significant traction in the battle against Covid-19. A plethora of contact tracing apps have been developed and deployed in several countries around the world. However, people are rightfully concerned about the security and privacy risks of such applications. To this end, the contribution of this w...
Chapter
Full-text available
Video surveillance on a massive scale can be a vital tool for law enforcement agencies. To mitigate the serious privacy concerns of wide-scale video surveillance, researchers have designed secure and privacy-preserving protocols that obliviously match live feeds against a suspects’ database. However, existing approaches provide stringent privacy gu...
Preprint
Full-text available
Contact tracing promises to help fight the spread of COVID–19 via an early detection of possible contagion events. To this end, most existing solutions share the following architecture: smartphones continuously broadcast random beacons that are intercepted by nearby devices and stored into their local contact logs. In this article, we propose an Io...
Article
Full-text available
Today’s society has a fundamental need for security and anonymity. Well suited, real-life scenarios such as whistleblower reports, intelligence service operations, and the ability to communicate within oppressive governments, call for such fundamental needs. The contribution and focus of this paper is the study of anonymous communications in the co...
Conference Paper
Full-text available
We propose a density-based model to detect communities of users in geo-social networks that are both socially and spatially cohesive. After formally defining the model and the geo-social distance measure it relies on, we present an algorithm that correctly identifies the underlying communities. We assess the effectiveness of our method using novel...
Chapter
Wireless sensor network (WSN) systems often need to support real time periodic queries of physical environments. In this work, we focus on periodic queries with sufficiently long time horizon in duty-cycled sensor networks. For each periodic query issued by a control center in a WSN, after the source sensors produced the sensory data, the data are...
Conference Paper
Full-text available
Online Social Networks (OSNs), such as Facebook and Twitter, are popular platforms that enable users to interact and socialize through their networked devices. The social nature of such applications encourages users to share a great amount of personal data with other users and the OSN service providers, including pictures, personal views, location...
Conference Paper
Full-text available
The proliferation of renewable energy systems and high-capacity batteries has enabled customers to trade their excess energy on the market in a peer-to-peer manner through the smart grid. At the same time, electric vehicles (EVs) are enjoying widespread acceptance, leading to a higher demand for charging stations. In this paper, we propose a system...
Conference Paper
Online Social Networks (OSNs), such as Facebook and Twitter, are popular platforms that enable users to interact and socialize through their networked devices. However, the social nature of such applications forces users to share a great amount of personal data with other users and the OSN service providers, including pictures, location check-ins,...
Article
The exponential growth of connected wireless devices has led to a depletion of the available wireless spectrum. To this end, dynamic spectrum access (DSA) has been proposed as a viable framework for maximizing the usability of the wireless spectrum by allowing some portions of it to be accessed and used in a dynamic manner. Contrary to the legacy f...
Article
Proximity detection is an emerging technology in Geo-Social Networks that notifies mobile users when they are in proximity. Nevertheless, users may be unwilling to participate in such applications if they are required to disclose their exact locations to a centralized server and/or their social friends. To this end, private proximity detection prot...
Article
Dynamic spectrum access (DSA) is a novel communication paradigm that enables wireless clients to utilize statically allocated radio channels that are currently idle. Specifically, in the database-driven DSA model, clients learn their geographic location through a GPS device and use this location to retrieve a list of available channels from a centr...
Conference Paper
Similar document detection is a well-studied problem with important application domains, such as plagiarism detection, document archiving, and patent/copyright protection. Recently, the research focus has shifted towards the privacy-preserving version of the problem, in which two parties want to identify similar documents within their respective da...
Conference Paper
The massive production of digital data and the complexity of the underlying data management, motivate individuals and enterprises to outsource their computational needs to the cloud. While popular cloud computing platforms provide flexible and inexpensive solutions, they do so with minimal support for data security and privacy. As a result, owners...
Conference Paper
Proximity detection is an emerging technology in Geo-Social Networks that notifies mobile users when they are in proximity. Nevertheless, users may be unwilling to participate in such applications if they are required to disclose their exact locations to a centralized server and/or their social friends. To this end, private proximity detection prot...
Article
Full-text available
Computational Private Information Retrieval (cPIR) protocols allow a client to retrieve one bit from a database, without the server inferring any information about the queried bit. These protocols are too costly in practice because they invoke complex arithmetic operations for every bit of the database. In this paper, we present pCloud, a distribut...
Conference Paper
Database queries present a potential privacy risk to users, as they may disclose sensitive information about the person issuing the query. Consequently, privacy preserving query processing has gained significant attention in the literature, and numerous techniques have been proposed that seek to hide the content of the queries from the database ser...
Article
Full-text available
With the popularity of location-based services and the abundant usage of smart phones and GPS-enabled devices, the necessity of outsourcing spatial data has grown rapidly over the past few years. Meanwhile, the fast arising trend of Cloud storage and Cloud computing services has provided a flexible and cost-effective platform for hosting data from...
Conference Paper
Full-text available
With the popularity of location-based services and the abundant usage of smart phones and GPS enabled devices, the necessity of outsourcing spatial data has grown rapidly over the past few years. Nevertheless, in the database outsourcing paradigm, the authentication of the query results at the client remains a challenging problem. In this paper, we...
Article
Full-text available
The tremendous growth of the Internet has significantly reduced the cost of obtaining and sharing information about individuals, raising many concerns about user privacy. Spatial queries pose an additional threat to privacy because the location of a query may be sufficient to reveal sensitive information about the querier. In this paper we focus on...
Article
Full-text available
Wireless data broadcast is a promising technique for information dissemination that leverages the computational capabilities of the mobile devices, in order to enhance the scalability of the system. Under this environment, the data are continuously broadcast by the server, interleaved with some indexing information for query processing. Clients may...
Conference Paper
Full-text available
Recent advances in wireless communications and positioning devices have generated a tremendous amount of interest in the continuous monitoring of spatial queries. However, such applications can incur a heavy burden on the data owner (DO), due to very frequent location updates. Database outsourcing is a viable solution, whereby the DO delegates its...
Article
We study the continuous evaluation of spatial join queries and extensions thereof, defined by interesting combinations of sensor readings (events) that co-occur in a spatial neigh- borhood. An example of such a pattern is "a high temper- ature reading in the vicinity of at least four high-pressure readings". We devise acquisitional and distributed...
Conference Paper
Full-text available
Multiple target tracking (MTT) is a well-studied technique in the field of radar technology, which associates anonymized measurements with the appropriate object trajectories. This technique, however, suffers from combinatorial explosion, since each new measurement may potentially be associated with any of the existing tracks. Consequently, the com...
Article
Fair bandwidth allocation is an important mechanism for traffic management in the Internet. Round robin schedulers, such as Deficit Round Robin (DRR), are well-suited for implementing fair queueing in multi-Gbps routers, as they schedule packets in constant time regardless of the total number of active flows. The main drawback of these schemes, how...
Article
Full-text available
Broadcast-based peer-to-peer (P2P) networks, including flat (for example, Gnutella) and two-layer superpeer implementations (for example, Kazaa), are extremely popular nowadays due to their simplicity, ease of deployment, and versatility. The unstructured network topology, however, contains many cyclic paths, which introduce numerous duplicate mess...
Article
Full-text available
We study the continuous evaluation of spatial join queries and extensions thereof, defined by interesting combinations of sensor readings (events) that co-occur in a spatial neighbor- hood. An example of such a pattern is "a high temperature reading in the vicinity of at least four high-pressure readings". We devise protocols for 'in-network' evalu...
Conference Paper
Full-text available
PDAs, cellular phones and other mobile devices are now capable of supporting complex data manipulation operations. Here, we focus on ad-hoc spatial joins of datasets residing in multiple non-cooperative servers. Assuming that there is no mediator available, the spatial joins must be evaluated on the mobile device. Contrary to common applications th...
Conference Paper
Full-text available
Given a dataset P and a preference function f ,at op-k query retrieves the k tuples in P with the highest scores accord- ing to f . Even though the problem is well-studied in con- ventional databases, the existing methods are inapplicable to highly dynamic environments involving numerous long- running queries. This paper studies continuous monitori...
Article
In distributed web caching architectures, institutional proxies take advantage of their neighbors’ contents in order to reduce the number of requests forwarded to the server. Intuitively, the maximum benefit from this cooperation is expected when the proxies that exhibit similar requests are grouped together. The current practice is to follow a sta...
Article
Full-text available
Assume a set of moving objects and a central server that monitors their positions over time, while processing continuous nearest neighbor queries from geographically distributed clients. In order to always report up-to-date results, the server could constantly obtain the most recent position of all objects. However, this naive solution requires the...
Conference Paper
Full-text available
A top-k OLAP query groups measures with respect to some abstraction level of interesting dimensions and selects the k groups with the highest aggregate value. An example of such a query is “find the 10 combinations of product-type and month with the largest sum of sales”. Such queries may also be applied in a spatial database context, where objects...
Conference Paper
Full-text available
This paper proposes and solves a-autonomy and k-stops shortest path problems in large spatial databases. Given a source s and a destination d ,a na- autonomy query retrieves a sequence of data points connecting s and d, such that the distance between any two consecutive points in the path is not greater than a .A k-stops query retrieves a sequence...
Conference Paper
Server selection is an important function in any replication-based infrastructure, aiming at redirecting client requests to the "best" server according to some predefined metrics. Previous research work has mainly focused on client-side redirection schemes, where the client is responsible for the server selection process. Furthermore, previous work...
Article
Caching and replication have emerged as the two primary techniques for reducing the delay experienced by end-users when downloading web pages. Even though these techniques may benefit from each other, previous research work tends to focus on either one of them separately. In particular, caching has been studied mostly in the context of proxy server...
Conference Paper
Full-text available
Caching and replication have emerged as the two primary techniques for reducing the delay experienced by end users when downloading web pages. Even though these techniques may benefit from each other, previous research work tends to focus on either one of them separately. In this paper we investigate the potential performance gains by using a CDN s...
Conference Paper
Full-text available
The fundamental drawback of unstructured peer-to-peer (P2P) networks is the flooding-based query processing protocol that seriously limits their scalability. As a result, a significant amount of research work has focused on designing efficient search protocols that reduce the overall communication cost. What is lacking, however, is the availability...
Article
The Differentiated Services (DiffServ) architecture has been proposed by the Internet Engineering Task Force as a scalable solution for providing end-to-end Quality of Service (QoS) guarantees over the Internet. While the scalability of the data plane emerges from the definition of only a small number of different service classes, the issue of a sc...
Conference Paper
Full-text available
Mobile devices like PDAs are capable of retrieving informa- tion from various types of services. In many cases, the user requests cannot directly be processed by the service providers, if their hosts have limited query capabilities or the query combines data from vari- ous sources, which do not collaborate with each other. In this paper, we present...
Conference Paper
Full-text available
This paper proposes a general framework for searching large distributed repositories. Examples of such repositories include sites with music/video content, distributed digital libraries, distributed caching systems, etc. The framework is based on the concept of neighborhood; each client keeps a list of the most beneficial sites according to past ex...
Conference Paper
Full-text available
In a generic cooperative caching architecture, web proxies form a mesh network. When a proxy cannot satisfy a request, it forwards the request to the other nodes of the mesh. Since a local cache cannot fulfill the majority of the arriving requests (typical values of the local hit ratio are about 30-50%), the volume of queries diverted to neighborin...
Article
Full-text available
This paper proposes a general framework for searching large distributed repositories. Examples of such repositories include sites with music/video content, distributed digital libraries, distributed caching systems etc. The framework is based on the concept of neighborhood; each client keeps a list of the most beneficial sites according to past exp...
Article
Full-text available
Video prefetching is a technique that has been proposed for the transmission of variable-bit-rate (VBR) videos over packet-switched networks. The objective of these protocols is to prefetch future frames at the customers' set-top box (STB) during light load periods. Experimental results have shown that video prefetching is very effective and it ach...
Conference Paper
Full-text available
The differentiated services (DiffServ) architecture has been proposed as a scalable solution for delivering end-to-end quality of service (QoS) guarantees over the Internet. While the scalability of the data plane emerges from the definition of only a small number of different service classes, the issue of a scalable control plane is still an open...
Conference Paper
Full-text available
During the past few years, new types of Internet applications which require performance beyond the best-effort service that is provided by the current Internet have emerged. These applications include the transmission of voice and video, which require a fixed end-to-end delay bound in order for the end-user to perceive an acceptable level of servic...
Conference Paper
Full-text available
Video prefetching has been proposed previously for the transmission of variable-bit-rate (VBR) video over a packet-switched network. The objective of these protocols is to prefetch future frames to be stored at the customer's set-top box (STB) in periods of low link utilization. Experimental results have shown that video prefetching is very effecti...
Conference Paper
Full-text available
A moving cluster is defined by a set of objects that move close to each other for a long time interval. Real-life examples are a group of migrating animals, a convoy of cars moving in a city, etc. We study the discovery of moving clusters in a database of object trajectories. The difference of this problem compared to clustering trajectories and mi...
Article
Transmission of variable-bit-rate (VBR) video over packet-switched networks is a very challenging problem, and has received much attention in the research community. The burstiness of VBR video makes it very hard to design efficient transmission schemes that will achieve a high level of network utilization. Promising work has been done recently for...

Network

Cited By