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About

I've received my MsC (2009) and PhD (2017) in Informatics Engineering from the University of Porto. I'm a researcher at the Centre for Telecommunications and Multimedia (CTM). I'm also an Invited Assistant Professor at the Department of Informatics Engineering (DEI) from the Faculty of Engineering of the Univeristy of Porto (FEUP). My reasearch interests include wireless networks, network simulation, and security.

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Publications

2017

Mistrustful P2P: Deterministic privacy-preserving P2P file sharing model to hide user content interests in untrusted peer-to-peer networks

Authors
da Silva, PM; Dias, J; Ricardo, M;

Publication
COMPUTER NETWORKS

Abstract
P2P networks endowed individuals with the means to easily and efficiently distribute digital media over the Internet, but user legal liability issues may be raised as they also facilitate the unauthorized distribution and reproduction of copyrighted material. Traditional P2P file sharing systems focus on performance and scalability, disregarding any privacy or legal issues that may arise from their use. Lacking alternatives, and unaware of the privacy issues that arise from relaying traffic of insecure applications, users have adopted anonymity systems for P2P file sharing. This work aims at hiding user content interests from malicious peers through plausible deniability. The Mistrustful P2P model is built on the concept of mistrusting all the entities participating in the P2P network, hence its name. It provides a deterministic and configurable privacy protection that relies on cover content downloads to hide user content interests, has no trust requirements, and introduces several mechanisms to prevent user legal liability and reduce network overhead while enabling timely content downloads. We extend previous work on the Mistrustful P2P model by discussing its legal and ethical framework, assessing its feasibility for more use cases, providing a security analysis, comparing it against a traditional P2P file sharing model, and further defining and improving its main mechanisms.

2016

Mistrustful P2P: Privacy-preserving File Sharing Over Untrustworthy Peer-to-Peer Networks

Authors
da Silva, PM; Dias, J; Ricardo, M;

Publication
2016 IFIP NETWORKING CONFERENCE (IFIP NETWORKING) AND WORKSHOPS

Abstract
Peer-to-Peer networks are extensively used for largescale file sharing. As more information flows through these networks, people are becoming increasingly concerned about their privacy. Traditional P2P file sharing systems provide performance and scalability at the cost of requiring peers to publicly advertise what they download. Several P2P privacyenhancing systems have been proposed but they still require peers to advertise, either fully or partially, what they download. Lacking alternatives, users have adopted anonymity systems for P2P file sharing, misunderstanding the privacy guarantees provided by such systems, in particular when relaying traffic of insecure applications such as BitTorrent. Our goal is to prevent any malicious peer(s) from ascertaining users' content interests so that plausible deniability always applies. We propose a novel P2P file sharing model, Mistrustful P2P, that (1) supports file sharing over open and untrustworthy P2P networks, (2) requires no trust between users by avoiding the advertisement of what peers download or miss, and (3) still ensures deterministic protection of user's interests against attacks of size up to a configured privacy protection level. We hope that our model can pave the ground for a new generation of privacyenhancing systems that take advantage of the new possibilities it introduces. We validate Mistrustful P2P through simulation, and demonstrate its feasibility.

2015

Storm: Rateless MDS erasure codes

Authors
da Silva, PM; Dias, J; Ricardo, M;

Publication
Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering, LNICST

Abstract
Erasure codes have been employed in a wide range of applications to increase content availability, improve channel reliability, or to reduce downloading time. For several applications, such as P2P file sharing, MDS erasure codes are more suitable as the network is typically the most constrained resource, not the CPU. Rateless MDS erasure codes also enable to adjust encoding and decoding algorithms as function of dynamic variables to maximize erasure coding gains. State-of-the-art MDS erasure codes are either fixed-rate or have practical limitations. We propose Storm erasure codes, a rateless MDS construction of Reed- Solomon codes over the finite field (formula presented), where p is a Mersenne prime. To the best of our knowledge, we are the first to propose a rateless construction (n can be increased in steps of k) with (formula presented) encoding time complexity and min (formula presented) upper bound for decoding time complexity. We provide the complexity analysis of encoding and decoding algorithms and evaluate Storm’s performance.

2015

CIDRarchy: CIDR-based ns-3 routing protocol for large scale network simulation

Authors
da Silva, PM; Dias, J; Ricardo, M;

Publication
SIMUTOOLS 2015 - 8th EAI International Conference on Simulation Tools and Techniques

Abstract
ns-3 is the successor of ns-2, the most popular network simulator. Network simulators such as ns-3 play an important role on understanding, designing, and building Internet systems. But simulations are only as good as their models, and the simulation of large scale Internet systems using accurate and complex models is a challenging task. ns-3 simulates realistically the network stack but the scale and complexity of the Internet topology is, from our point of view, limited by the IP forwarding operations. This work proposes CIDRarchy, an IPv4 routing protocol for ns-3 that uses CIDR as the base to create an hierarchical Internet-like network topology that enables (1) IP forwarding with constant time complexity and automatic IPv4 address assignment, and (2) the implementation of an ns-3 helper to ease network topology creation. We implemented CIDRarchy, evaluated its performance, and obtained simulation time reduction over existing ns-3 routing protocols implementations that can reach over one order of magnitude. Copyright © 2015 ICST.

2010

Securing Webmail using S/MIME and Cryptographic Timestamps

Authors
Pedro Miguel Silva; Jaime Sousa Dias; Manuel Ricardo

Publication
CRC 2010 - 10ª Conferência sobre Redes de Computadores, Braga, Portugal

Abstract