35 research outputs found
Digital Sovereignty Strategies for Every Nation
Digital Sovereignty must be on the agenda of every modern nation. Digital
technology is becoming part of our life details, from the vital essentials,
like food and water management, to transcendence in the Metaverse and Space.
Protecting these digital assets will, therefore, be inevitable for a modern
country to live, excel and lead. Digital Sovereignty is a strategic necessity
to protect these digital assets from the monopoly of friendly rational states,
and the threats of unfriendly Malicious states and behaviors. In this work, we
revisit the definition and scope of digital sovereignty through extending it to
cover the entire value chain of using, owning, and producing digital assets. We
emphasize the importance of protecting the operational resources, both raw
materials and human expertise, in addition to research and innovation necessary
to achieve sustainable sovereignty. We also show that digital sovereignty by
autonomy is often impossible, and by mutual cooperation is not always
sustainable. To this end, we propose implementing digital sovereignty using
Nash Equilibrium, often studied in Game Theory, to govern the relation with
Rational states. Finally, we propose a digital sovereignty agenda for different
country's digital profiles, based on their status quo, priorities, and
capabilities. We survey state-of-the-art digital technology that is useful to
make the current digital assets sovereign. Additionally, we propose a roadmap
that aims to develop a sovereign digital nation, as close as possible to
autonomy. Finally, we draw attention to the need of more research to better
understand and implement digital sovereignty from different perspectives:
technological, economic, and geopolitical
BFT Selection
International audienceOne-size-fits-all protocols are hard to achieve in Byzantine fault tolerance (BFT). As an alternative, BFT users, e.g., enterprises, need an easy and efficient method to choose the most convenient protocol that matches their preferences best. The various BFT protocols that have been proposed so far differ significantly in their characteristics and performance which makes choosing the `preferred' protocol hard. In addition, if the state of the deployed system is too fluctuating, then perhaps using multiple protocols at once is needed; this requires a dynamic selection mechanism to move from one protocol to another. In this paper, we present the first BFT selection model and algorithm that can be used to choose the most convenient protocol according to user preferences. The selection algorithm applies some mathematical formulas to make the selection process easy and automatic. The algorithm operates in three modes: Static, Dynamic, and Heuristic. The Static mode addresses the cases where a single protocol is needed; the Dynamic mode assumes that the system conditions are quite fluctuating and thus requires runtime decisions, and the Heuristic mode is similar to the Dynamic mode but it uses additional heuristics to improve user choices. We give some examples to describe how selection occurs. We show that our approach is automated, easy, and yields reasonable results that match reality. To the best of our knowledge, this is the first work that addresses selection in BFT
Byzantine fault tolerance from static selection to dynamic switching
La Tolérance aux pannes Byzantines (BFT) est de plus en plus crucial avec l'évolution d'applications et en raison de la croissance de l'innovation technologique en informatique. Bien que des dizaines de protocoles BFT aient été introduites dans les années précédentes, leur mise en œuvre ne semble pas satisfaisant. Pour faire face à cette complexité, due à la dependence d'un protocol d'une situation, nous tentons une approche qui permettra de sélectionner un protocole en fonction d'une situation. Ceci nous paraît, en s'inspirant de tout système d'encrage, comme une démarche nécessaire pour aborder la problématique de la BFT. Dans cette thèse, nous introduisons un modèle de sélection ainsi que l'algorithme qui permet de simplifier et d'automatiser le processus d'élection d'un protocole. Ce mécanisme est conçu pour fonctionner selon 3 modes : statique, dynamique et heuristique. Les deux derniers modes, nécessitent l'introduction d'un système réactif, nous ont conduits à présenter un nouveau modèle BFT : Adapt. Il réagit à tout changement et effectue, d'une manière adaptée, la commutation entre les protocoles d'une façon dynamique. Le mode statique permet aux utilisateurs de BFT de choisir un protocole BFT en une seule fois. Ceci est très utile dans les services Web et les " Clouds " où le BFT peut être fournit comme un service inclut dans le contrat (SLA). Ce mode est essentiellement conçu pour les systèmes qui n'ont pas trop d'états fluctuants. Pour ce faire, un processus d'évaluation est en charge de faire correspondre, à priori, les préférences de l'utilisateur aux profils du protocole BFT nommé, en fonction des critères de fiabilité et de performance. Le protocole choisi est celui qui réalise le meilleur score d'évaluation. Le mécanisme est bien automatisé à travers des matrices mathématiques, et produit des sélections qui sont raisonnables. D'autres systèmes peuvent cependant avoir des conditions flottantes, il s'agit de la variation des charges ou de la taille de message qui n'est pas fixe. Dans ce cas, le mode statique ne peut continuer à être efficace et risque de ne pas pouvoir s'adapter aux nouvelles conditions. D'où la nécessité de trouver un moyen permettant de répondre aux nouvelles exigences d'une façon dynamique. Adapt combine un ensemble de protocoles BFT ainsi que leurs mécanismes de commutation pour assurer l'adaptation à l'évolution de l'état du système. Par conséquent, le "Meilleur" protocole est toujours sélectionné selon l'état du système. On obtient ainsi une qualité optimisée de service, i.e., la fiabilité et la performance. Adapt contrôle l'état du système grâce à ses mécanismes d'événements, et utilise une méthode de "Support Vecor Regrssion" pour conduire aux prédictions en temps réel pour l'exécution des protocoles (par exemple, débit, latence, etc.). Ceci nous conduit aussi à un mode heuristique. En utilisant des heuristiques prédéfinies, on optimise les préférences de l'utilisateur afin d'améliorer le processus de sélection. L'évaluation de notre approche montre que le choix du "meilleur" protocole est automatisé et proche de la réalité de la même façon que dans le mode statique. En mode dynamique, Adapt permet toujours d'obtenir la performance optimale des protocoles disponibles. L'évaluation démontre, en plus, que la performance globale du système peut être améliorée de manière significative. Explorer d'autres cas qui ne conduisent pas de basculer entre les protocoles. Ceci est rendu possible grâce à la réalisation des prévisions d'une grande precision qui peuvent atteindre plus de 98% dans de nombreux cas. La thèse montre que cette adaptabilité est rendue possible grâce à l'utilisation des heuristiques dans un mode dynamique.Byzantine Fault Tolerance (BFT) is becoming crucial with the revolution of online applications and due to the increasing number of innovations in computer technologies. Although dozens of BFT protocols have been introduced in the previous decade, their adoption by practitioners sounds disappointing. To some extant, this indicates that existing protocols are, perhaps, not yet too convincing or satisfactory. The problem is that researchers are still trying to establish 'the best protocol' using traditional methods, e.g., through designing new protocols. However, theoretical and experimental analyses demonstrate that it is hard to achieve one-size-fits-all BFT protocols. Indeed, we believe that looking for smarter tac-tics like 'fasten fragile sticks with a rope to achieve a solid stick' is necessary to circumvent the issue. In this thesis, we introduce the first BFT selection model and algorithm that automate and simplify the election process of the 'preferred' BFT protocol among a set of candidate ones. The selection mechanism operates in three modes: Static, Dynamic, and Heuristic. For the two latter modes, we present a novel BFT system, called Adapt, that reacts to any potential changes in the system conditions and switches dynamically between existing BFT protocols, i.e., seeking adaptation. The Static mode allows BFT users to choose a single BFT protocol only once. This is quite useful in Web Services and Clouds where BFT can be sold as a service (and signed in the SLA contract). This mode is basically designed for systems that do not have too fuctuating states. In this mode, an evaluation process is in charge of matching the user preferences against the profiles of the nominated BFT protocols considering both: reliability, and performance. The elected protocol is the one that achieves the highest evaluation score. The mechanism is well automated via mathematical matrices, and produces selections that are reasonable and close to reality. Some systems, however, may experience fluttering conditions, like variable contention or message payloads. In this case, the static mode will not be e?cient since a chosen protocol might not fit the new conditions. The Dynamic mode solves this issue. Adapt combines a collection of BFT protocols and switches between them, thus, adapting to the changes of the underlying system state. Consequently, the 'preferred' protocol is always polled for each system state. This yields an optimal quality of service, i.e., reliability and performance. Adapt monitors the system state through its Event System, and uses a Support Vector Regression method to conduct run time predictions for the performance of the protocols (e.g., throughput, latency, etc). Adapt also operates in a Heuristic mode. Using predefined heuristics, this mode optimizes user preferences to improve the selection process. The evaluation of our approach shows that selecting the 'preferred' protocol is automated and close to reality in the static mode. In the Dynamic mode, Adapt always achieves the optimal performance among available protocols. The evaluation demonstrates that the overall system performance can be improved significantly too. Other cases explore that it is not always worthy to switch between protocols. This is made possible through conducting predictions with high accuracy, that can reach more than 98% in many cases. Finally, the thesis shows that Adapt can be smarter through using heursitics
As secure as possible eventual consistency: Work in progress
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.The research leading to these results has received funding from the European Union’s Horizon2020 - The EU Framework Programme for Research and Innovation 2014-2020, under Grant agreement No. 732505, Light Kone project.Project “TEC4 Growth- Pervasive Intelligence, Enhancers and Proofs of Concept with Industrial Impact / NORTE-01-0145-FEDER-000020” is financed by the NorthPortugal Regional Operational Programme(NORTE2020), under the PORTUGAL 2020 Partnership Agreement, and through the European Regional Development Fund (ERDF).info:eu-repo/semantics/publishedVersio
Exactly-once quantity transfer
Strongly consistent systems supporting distributed transactions can be prone to high latency and do not tolerate partitions. The present trend of using weaker forms of consistency, to achieve high availability, poses notable challenges in writing applications due to the lack of linearizability, e.g., to ensure global invariants, or perform mutator operations on a distributed datatype. This paper addresses a specific problem: the exactly-once transfer of a "quantity" from one node to another on an unreliable network (coping with message duplication, loss, or reordering) and without any form of global synchronization. This allows preserving a global property (the sum of quantities remains unchanged) without requiring global linearizability and only through using pairwise interactions between nodes, therefore allowing partitions in the system. We present the novel quantity-transfer algorithm while focusing on a specific use-case: a redistribution protocol to keep the quantities in a set of nodes balanced; in particular, averaging a shared real number across nodes. Since this is a work in progress, we briefly discuss the correctness of the protocol, and we leave potential extensions and empirical evaluations for future work.This work is financed by the FCT Fundação para a Ciência e a Tecnologia (Portuguese Foundation for Science and Technology) within project UID/EEA/50014/2013; and by the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement 609551, SyncFree project.info:eu-repo/semantics/publishedVersio
Efficient state-based CRDTs by decomposition
Eventual consistency is a relaxed consistency model used in large-scale distributed systems that seek better availability when consistency can be delayed. CRDTs are distributed data types that make eventual consistency of a distributed object possible and non ad-hoc. Specifically, state-based CRDTs achieve this through shipping the entire replica state that is, eventually, merged to other replicas ensuring conver- gence. This imposes a large communication overhead when the replica size or the number of replicas gets larger. In this work, we introduce a decomposable version of state-based CRDTs, called Delta State-based CRDTs (δ-CRDT). A δ-CRDT is viewed as a join of multiple fine-grained CRDTs of the same type, called deltas (δ). The deltas are produced by applying δ-mutators, on a replica state, which are mod- ified versions of the original CRDT mutators. This makes it possible to ship small deltas (or batches) instead of ship- ping the entire state. The challenges are to make the join of deltas equivalent to the join of the entire object in clas- sical state-based CRDTs, and to find a way to derive the δ-mutators. We address this challenge in this work, and we explore the minimal requirements that a communication al- gorithm must offer according to the guarantees provided by the underlying messaging middleware.Project Norte-01-0124-FEDER-000058 is co-financed by the North Portugal Regional Operational Program (ON.2 - O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF). Funding from the European Union Seventh Framework Program (FP7/2007-2013) with grant agreement 609551, SyncFree project.info:eu-repo/semantics/publishedVersio
Improving Independence of Failures in BFT
International audienceIndependence of failures is a basic assumption for the correctness of BFT protocols. In literature, this subject was addressed by providing N-version like abstractions. Though this can provide a good level of obfuscation against semantic- based attacks, if the replicas know each others identities then non-semantic attacks like DoS can still compromise all replicas together. In this paper, we address the obfuscation problem in a different way by keeping replicas unaware of each other. This makes it harder for attackers to sneak from one replica to another and reduces the impact of simultaneous attacks on all replicas. For this sake, we present a new obfuscated BFT protocol, called OBFT, where the replicas remain unaware of each other by exchanging their messages through the clients. Thus, OBFT assumes honest, but possibly crash-prone clients. We show that obfuscation in our context could not be achieved without this assumption, and we give possible applications where this assumption can be accepted. We evaluated our protocol on an Emulab cluster with a wide area topology. Our experiments show that the scalability and throughput of OBFT remain comparable to existing BFT protocols despite the obfuscation overhead
Exon: An oblivious exactly-once messaging protocol
TCP is typically the default transport protocol of choice for its supposed reliability, even for message-oriented middleware (e.g., ZeroMQ) or inter-actor communication (e.g., distributed Erlang). However, under network issues, TCP con-nections can fail, which requires ensuring both at-least-once and at-most-once delivery at the upper middleware layer. Moreover, the use of TCP at scale, in highly concurrent systems, can lead to drastic performance loss due to the need for TCP connection multiplexing and the resulting head-of-line blocking. This paper introduces Exon, an oblivious exactly-once messaging protocol, and a corresponding lightweight library implementation. Exon uses a novel strategy of a per-message four-way protocol to ensure oblivious exactly-once messaging, with on-demand protocol-level 'soft half-connections' that are established when needed and safely discarded. This achieves correctness, obliviousness, and performance, through merging and pipelining basic protocol mes-sages. The empirical evaluation of Exon demonstrates significant improvements in throughput and latency under packet loss, while maintaining a negligible overhead over TCP in healthy networks.Partially funded by project AIDA – Adaptive, Intelligent and Distributed Assurance Platform (POCI-01-0247-FEDER045907) co-financed by the European Regional Development Fund (ERDF) through the Operational Program for Competitiveness and Internationalisation (COMPETE 2020) and by the Portuguese Foundation for Science and Technology (FCT) under CMU Portugal
The Path to Fault- and Intrusion-Resilient Manycore Systems on a Chip
The hardware computing landscape is changing. What used to be distributed
systems can now be found on a chip with highly configurable, diverse,
specialized and general purpose units. Such Systems-on-a-Chip (SoC) are used to
control today's cyber-physical systems, being the building blocks of critical
infrastructures. They are deployed in harsh environments and are connected to
the cyberspace, which makes them exposed to both accidental faults and targeted
cyberattacks. This is in addition to the changing fault landscape that
continued technology scaling, emerging devices and novel application scenarios
will bring. In this paper, we discuss how the very features, distributed,
parallelized, reconfigurable, heterogeneous, that cause many of the imminent
and emerging security and resilience challenges, also open avenues for their
cure though SoC replication, diversity, rejuvenation, adaptation, and
hybridization. We show how to leverage these techniques at different levels
across the entire SoC hardware/software stack, calling for more research on the
topic