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Publicações

Publicações por CRACS

2025

Fast Computation of the Discrete Fourier Transform Square Index Coefficients

Autores
Queiroz, S; Vilela, P; Monteiro, H; Li, X;

Publicação
IEEE SIGNAL PROCESSING MAGAZINE

Abstract
Provides society information that may include news, reviews or technical notes that should be of interest to practitioners and researchers. © 2025 Elsevier B.V., All rights reserved.

2025

Delving Into Security and Privacy of Joint Communication and Sensing: A Survey

Autores
Martins, OG; Akesson, H; Gomes, M; Osorio, DPM; Sen, P; Vilela, JP;

Publicação
IEEE OPEN JOURNAL OF THE COMMUNICATIONS SOCIETY

Abstract
Joint Communication and Sensing (JCAS) systems are emerging as a core technology for next-generation wireless systems due to the potential to achieve higher spectral efficiency, energy savings, and new services beyond communications. This paper provides a review of the state-of-the-art in JCAS systems by focusing on obtrusive passive sensing capabilities and inherent security and privacy challenges that arise from the integration of communication and sensing. From this point of view, we discuss existing techniques for mitigating security and privacy issues, as well as important aspects for the designing of secure and privacy-aware JCAS systems. Additionally, we discuss future research directions by emphasizing on new enabling technologies and their integration on JCAS systems along with their role in privacy and security aspects. We also discuss the required modifications to existing systems and the design of new systems with privacy and security awareness, where the challenging trade-offs between security, privacy and performance of the JCAS system must be considered.

2025

WiFi-Based Location Tracking: A Still Open Door on Laptops

Autores
Cunha, M; Mendes, R; de Montjoye, YA; Vilela, JP;

Publicação
IEEE OPEN JOURNAL OF THE COMPUTER SOCIETY

Abstract
Location privacy is a major concern in the current digital society, due to the sensitive information that can be inferred from location data. This has led smartphones' Operating Systems (OSs) to strongly tighten access to location information in the last few years. The same tightening has, however, not yet happened when it comes to our second most carried around device: the laptop. In this work, we demonstrate the privacy risks resulting from the fact that major laptop OSs still expose WiFi data to installed software, thus enabling to infer location information from WiFi Access Points (APs). Using data collected in a real-world experiment, we show that laptops are often carried along with smartphones and that a large fraction of our mobility profile can be inferred from WiFi APs accessed on laptops, thus concluding on the need to protect the access to WiFi data on laptops.

2025

On the Difficulty of NOT being Unique: Fingerprinting Users from Wi-Fi Data in Mobile Devices

Autores
Cunha, M; Mendes, R; de Montjoye, YA; Vilela, JP;

Publicação
40TH ANNUAL ACM SYMPOSIUM ON APPLIED COMPUTING

Abstract
The pervasiveness of mobile devices has fostered a multitude of services and applications, but also raised serious privacy concerns. In order to avoid users' tracking and/or users' fingerprinting, smartphones have been tightening the access to unique identifiers. Nevertheless, smartphone applications can still collect diverse data from available sensors and smartphone resources. Using real-world data from a field study we performed, this paper demonstrates the possibility of fingerprinting users from Wi-Fi data in mobile devices and the consequent privacy impact. From the performed analysis, we concluded that a single snapshot of a set of scanned Wi-Fi BSSIDs (MAC addresses) per user is enough to uniquely identify about 99% of the users. In addition, the most frequent Wi-Fi BSSID is sufficient to re-identify more than 90% of the users, a percentage that goes up to 97% of the users with the top-2 scanned BSSIDs. The Wi-Fi SSID (network name) also leads to a re-identification risk of about 83% and 97% with 1 and 2 of the strongest Wi-Fi Access Points (APs), respectively.

2025

Blockchain Hybrid-model Scheme for Scalable Cross-domain Authorisation

Autores
Mukhandi, M; Granjal, J; Vilela, JP;

Publicação
Blockchain: Research and Applications

Abstract

2024

Topic Extraction: BERTopic's Insight into the 117th Congress's Twitterverse

Autores
Mendonça, M; Figueira, A;

Publicação
INFORMATICS-BASEL

Abstract
As social media (SM) becomes increasingly prevalent, its impact on society is expected to grow accordingly. While SM has brought positive transformations, it has also amplified pre-existing issues such as misinformation, echo chambers, manipulation, and propaganda. A thorough comprehension of this impact, aided by state-of-the-art analytical tools and by an awareness of societal biases and complexities, enables us to anticipate and mitigate the potential negative effects. One such tool is BERTopic, a novel deep-learning algorithm developed for Topic Mining, which has been shown to offer significant advantages over traditional methods like Latent Dirichlet Allocation (LDA), particularly in terms of its high modularity, which allows for extensive personalization at each stage of the topic modeling process. In this study, we hypothesize that BERTopic, when optimized for Twitter data, can provide a more coherent and stable topic modeling. We began by conducting a review of the literature on topic-mining approaches for short-text data. Using this knowledge, we explored the potential for optimizing BERTopic and analyzed its effectiveness. Our focus was on Twitter data spanning the two years of the 117th US Congress. We evaluated BERTopic's performance using coherence, perplexity, diversity, and stability scores, finding significant improvements over traditional methods and the default parameters for this tool. We discovered that improvements are possible in BERTopic's coherence and stability. We also identified the major topics of this Congress, which include abortion, student debt, and Judge Ketanji Brown Jackson. Additionally, we describe a simple application we developed for a better visualization of Congress topics.

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