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I hold a Masters degree in Informatics and Telecommunications from Arts, Sciences and Technology University, Lebanon.I hold Bachelor degree in Informatics and Technology from ULF University, Lebanon.I am a PhD Student at MAPi (A joint Doctoral Programme in Computer Science of the University of Minho, the University of Aveiro and the University of Porto), I am also a researcher at HASLab/INESC TEC located in Minho University, Braga, Portugal.

I am interested in the domain of distributed systems. I am working on my thesis now, the subject is: “Extending Conflict-free Replicated Data Types Fault Models".

The thesis aims to extend the fault model of CRDTs to address Byzantine faults, rational behaviors, etc.This work aims at extending the fault model addressed in literature for CRDTs by suggestions considering Byzantine faults as it represents the strongest fault model, it exists in practice, and it has been studied very well in literature.

My supervisors are: Dr. Ali Shoker and Prof. José Bacelar Almeida.

Hosting Research Unit : High-Assurance Software Lab (HASLab)/INESC TEC & Univ. of Minho.

External Monitor : Prof. Alysson Bessani, universidade de Lisboa



  • Name

    Houssam Ahmad Yactin
  • Cluster

    Computer Science
  • Role

    External Student
  • Since

    15th March 2016


As Secure as Possible Eventual Consistency: Work in Progress

Shoker, A; Yactine, H; Baquero, C;

Proceedings of the 3rd International Workshop on Principles and Practice of Consistency for Distributed Data, PaPoC@EuroSys 2017, Belgrade, Serbia, April 23 - 26, 2017

Eventual consistency (EC) is a relaxed data consistency model that, driven by the CAP theorem, trades prompt consistency for high availability. Although, this model has shown to be promising and greatly adopted by industry, the state of the art only assumes that replicas can crash and recover. However, a Byzantine replica (i.e., arbitrary or malicious) can hamper the eventual convergence of replicas to a global consistent state, thus compromising the entire service. Classical BFT state machine replication protocols cannot solve this problem due to the blocking nature of consensus, something at odd with the availability via replica divergence in the EC model. In this work in progress paper, we introduce a new secure highly available protocol for the EC model that assumes a fraction of replicas and any client can be Byzantine. To respect the essence of EC, the protocol gives priority to high availability, and thus Byzantine detection is performed off the critical path on a consistent data offset. The paper concisely explains the protocol and discusses its feasibility. We aim at presenting a more comprehensive and empirical study in the future. © 2017 ACM.