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Publicações

2026

Obscura: Enabling Ephemeral Proxies for Traffic Encapsulation in WebRTC Media Streams Against Cost-Effective Censors

Autores
Afonso Vilalonga; Kevin Gallagher; João S. Resende; Henrique Domingos;

Publicação
Proceedings on Privacy Enhancing Technologies

Abstract
Recent research on online censorship has provided valuable insights into common censorship strategies and censors' tolerance for collateral damage. A consistent finding across these studies is that censors tend to favour cost-effective techniques such as proxy enumeration, active probing, and deep packet inspection (DPI), rather than more complex and non-deterministic methods such as deep learning-based traffic analysis. For example, a recent study on the Snowflake censorship evasion system reinforced this finding by demonstrating that authoritarian regimes primarily relied on DPI to target the system. However, as censorship techniques continue to evolve, two critical questions arise: (1) What future attack vectors are likely to emerge based on current research and observed censor capabilities? (2) How can these emerging threats, along with previously utilised censorship methods, be effectively mitigated? In this paper, we present Obscura, a censorship evasion system designed to resist cost-effective, historically grounded censorship techniques while also defending against a class of plausible future attacks within a cost-effective threat model targeting WebRTC-based censorship evasion systems. Obscura is built upon four core features: (1) encapsulation of traffic within WebRTC media streams, (2) the use of a reliability layer, (3) support for both browser-based and Pion-based clients and proxy instances, and (4) the use of ephemeral proxies. Each feature is intended to mitigate either a known attack observed in the wild or a theoretically plausible attack consistent with the capabilities of a cost-effective censor. We provide a security analysis to justify our design choices and a performance evaluation to demonstrate that Obscura maintains reasonable throughput for typical online activities.

2026

A Secure Architecture for Supply-Chain Orders Exchange Between Textile and Clothing Companies

Autores
Torres, N; Chaves, A; Costa, T; Alves, M; Mota, B; Sousa, C; Malta, S; Pinto, P;

Publicação
OPTIMIZATION, LEARNING ALGORITHMS AND APPLICATIONS, OL2A 2025, PT II

Abstract
DIn the digital transformation of industrial sectors, data is a high-value business asset. How companies manage data between systems within the organization or through networks of business partners impacts their competitive factor. Technological maturity may imply several adversities, such as the lack of interoperability standards for simple and transparent data exchange. This paper presents an architecture that enables secure exchanges of supply chain orders between textile and clothing companies. This architecture is based on Electronic Business (eBIZ) 4.0 and International Data Spaces (IDS) frameworks, fostering trust and widespread adoption of platforms in the industry sector, particularly when handling sensitive supply chain information. The architecture was implemented and validated in 3 use cases with Enterprise Resource Plannings (ERPs) from the same vendor, different vendors, and communication from a ERP to a Web portal. Implementing the proposed architecture impacted efficiency, transparency, and accountability within the supply chain network. The lead times for purchases, provisioning, and the number of additional information requests in the ordering were reduced. In subcontracting, a reduction in non-conformities and an overall improvement in delivery times were verified. Moreover, logistics operations and communication with subcontractors were optimized, leading to faster order reception and reducing informal contacts.

2026

Preface

Autores
Proença, J; Fervari, R; Martins, MA; Kahle, R; Pluck, G;

Publicação
Lecture Notes in Computer Science

Abstract
[No abstract available]

2026

Software Engineering and Formal Methods. SEFM 2024 Collocated Workshops - ReacTS 2024 and CIFMA 2024, Aveiro, Portugal, November 4-5, 2024, Revised Selected Papers

Autores
Proença, J; Fervari, R; Martins, MA; Kahle, R; Pluck, G;

Publicação
SEFM

Abstract

2026

Optical Harmonic Vernier Effect: Conditions Required for Effective Sensitivity Amplification

Autores
Robalinho, P; Piaia, V; Ribeiro, AL; Silva, S; Frazao, O;

Publicação
JOURNAL OF LIGHTWAVE TECHNOLOGY

Abstract
This paper presents the conditions required for effective sensitivity amplification in the optical harmonic Vernier effect. Two distinct cases are analyzed: in the first, the sensor cavity is the shortest, while in the second, it is the longest. Based on the proposed theoretical model, supported by experimental results, it is concluded that, in the first case, the sensitivity associated with the spectral extremes increases with the order of the harmonic states. In contrast, in the second case, the sensitivity at the spectral extremes remains constant, regardless of the harmonic order. To evaluate the effectiveness of applying the optical Vernier effect and to differentiate between the two cases, a new formulation of the magnification factor (M-factor) is introduced. This leads to the definition of a novel figure of merit for the optical Vernier effect, denoted as (FoM(Vernier)). In Case 1, where harmonics are generated by increasing the reference cavity, the figure of merit assumes a value of (m + 1). In Case 2, where harmonics are generated by increasing the sensor cavity, the figure of merit remains constant at 1, regardless of the state order (whether fundamental or harmonic). This study also concludes that the observed increase in sensitivity is apparent rather than intrinsic, as the sensitivity curve produced by the optical Vernier effect mirrors that of a conventional interferometer.

2026

Accurate Determination of the Temperature Sensitivity of UV-Induced Fiber Bragg Gratings

Autores
Cosme, M; Pota, M; Preizal, J; Caldas, P; Oliveira, R; Nogueira, R; Araújo, FM; Cruz, JL; Rego, GM;

Publicação
SENSORS

Abstract
Over the past 18 months, we have performed hundreds of temperature characterizations of fiber Bragg gratings inscribed in different germanium-doped silica glass fibers. Under experimental conditions, the main conclusions are as follows: the temperature dependence of the temperature gauge factor or the normalized temperature sensitivity, K-T, was found to be quadratic in the -50-200 degrees C range, while it may be considered linear for the -20-100 degrees C range; K-T values at 20 degrees C vary from 5.176 x 10(-6) K-1, for a B/Ge co-doped fiber up to 6.724 x 10(-6) K-1, for a highly Ge-doped fiber; K-T does not depend on the hydrogen-loading process or the gratings coupling strength; K-T is essentially independent of wavelength in the 1500-1600 nm range, its value being accurately determined with a relative error similar to 0.2%; based on the accurate value of K-T = 6.165 x 10(-6) K-1, at 20 degrees C, obtained for gratings inscribed in the SMF-28 fiber, we calculated a value of 19.4 x 10(-6) K-1 for the thermo-optic coefficient of bulk germanium glass; and gratings produced by femtosecond-laser radiation and UV-laser radiation exhibit comparable values of K-T. The previous achievements allow, by having knowledge of K-T for a single grating, the accurate determination of the temperature dependence of the Bragg wavelength for any other grating inscribed in the same fiber; the presented methodology enables one to determine the unknown gratings' temperature sensitivity, typically with an error of 0.01 pm/degrees C, being, therefore, very useful in research labs and computer simulations. Thus, expressions for the temperature dependence of K-T for gratings inscribed in several fibers are given, as well as an expression for K-T as a function of the effective refractive index. We have also fully analyzed the potential sources of error in K-T determination.

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