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About

I am a senior researcher at INESC TEC (HASLab research unit) and invited assistant professor at the Department of Informatics of University of Minho, Braga, Portugal. I hold a PhD from the University of Toulouse, advised by Jean-Paul Bahsoun and mentored by Rachid Guerraoui. I've spent some time at IRIT (France), INSA de Lyon (France), and EPFL (Switzerland) twice in the past.

I am interested in understanding and building correct, scalable, available, resilient, secure, and efficient distributed systems. 
Currently, I am working Edge Computing (based on Conflict-free Replicated DataTypes), and Blockchain and Cryptocurrencies (PoW,PoX, and BFT).

Interest
Topics
Details

Details

001
Publications

2017

Sustainable blockchain through proof of exercise

Authors
Shoker, A;

Publication
16th IEEE International Symposium on Network Computing and Applications, NCA 2017, Cambridge, MA, USA, October 30 - November 1, 2017

Abstract

2015

Efficient State-Based CRDTs by Delta-Mutation

Authors
Almeida, PS; Shoker, A; Baquero, C;

Publication
Networked Systems - Third International Conference, NETYS 2015, Agadir, Morocco, May 13-15, 2015, Revised Selected Papers

Abstract
CRDTs are distributed data types that make eventual consistency of a distributed object possible and non ad-hoc. Specifically, state-based CRDTs ensure convergence through disseminating the entire state, that may be large, and merging it to other replicas; whereas operation-based CRDTs disseminate operations (i.e., small states) assuming an exactly-once reliable dissemination layer. We introduce Delta State Conflict-Free Replicated Datatypes (d-CRDT) that can achieve the best of both worlds: small messages with an incremental nature, disseminated over unreliable communication channels. This is achieved by defining d-mutators to return a delta-state, typically with a much smaller size than the full state, that is joined to both: local and remote states. We introduce the d-CRDT framework, and we explain it through establishing a correspondence to current state-based CRDTs. In addition, we present an anti-entropy algorithm that ensures causal consistency, and two d-CRDT specifications of well-known replicated datatypes. © Springer International Publishing Switzerland 2015.

2015

Making BFT Protocols Really Adaptive

Authors
Bahsoun, JP; Guerraoui, R; Shoker, A;

Publication
2015 IEEE International Parallel and Distributed Processing Symposium, IPDPS 2015, Hyderabad, India, May 25-29, 2015

Abstract
Many state-machine Byzantine Fault Tolerant (BFT) protocols have been introduced so far. Each protocol addressed a different subset of conditions and use-cases. However, if the underlying conditions of a service span different subsets, choosing a single protocol will likely not be a best fit. This yields robustness and performance issues which may be even worse in services that exhibit fluctuating conditions and workloads. In this paper, we reconcile existing state-machine BFT protocols in a single adaptive BFT system, called ADAPT, aiming at covering a larger set of conditions and use-cases, probably the union of individual subsets of these protocols. At anytime, a launched protocol in ADAPT can be aborted and replaced by another protocol according to a potential change (an event) in the underlying system conditions. The launched protocol is chosen according to an 'evaluation process' that takes into consideration both: protocol characteristics and its performance. This is achieved by applying some mathematical formulas that match the profiles of protocols to given user (e.g., service owner) preferences. ADAPT can assess the profiles of protocols (e.g., throughput) at run-time using Machine Learning prediction mechanisms to get accurate evaluations. We compare ADAPT with well known BFT protocols showing that it outperforms others as system conditions change and under dynamic workloads. © 2015 IEEE.

Supervised
thesis

2016

Optimizing Operation-based Conflict-free Replicated Data Types

Author
Georges Younes

Institution
UM

2016

Extending Conflict free Replicated DataTypes fault models

Author
Houssam Yactine

Institution
UM