Game Theoretical Framework for Analyzing Blockchains Robustness

In this paper we propose a game theoretical framework in order to formally characterize the robustness of blockchains systems in terms of resilience to rational deviations and immunity to Byzantine behaviors. Our framework includes necessary and sufficient conditions for checking the immunity and resilience of games and an original technique for composing games that preserves the robustness of individual games. We prove the practical interest of our formal framework by characterizing the robustness of various blockchain protocols: Bitcoin (the most popular permissionless blockchain), Tendermint (the first permissioned blockchain used by the practitioners), Lightning Network, a side-chain protocol and a cross-chain swap protocol. For each one of the studied protocols we identify upper and lower bounds with respect to their resilience and immunity (expressed as no worse payoff than the initial state) face to rational and Byzantine behaviors

Brief Announcement: Game Theoretical Framework for Analyzing Blockchains Robustness

Blockchains systems evolve in complex environments that mix classical patterns of faults (e.g crash faults, transient faults, Byzantine faults, churn) with selfish, rational or irrational behaviors typical to economical systems. In this paper we propose a game theoretical framework in order to formally characterize the robustness of blockchains systems in terms of resilience to rational deviations and immunity to Byzantine behaviors. Our framework includes necessary and sufficient conditions for checking the immunity and resilience of games and a new technique for composing games that preserves the robustness of individual games. We prove the practical interest of our formal framework by characterizing the robustness of three different protocols popular in blockchain systems: a HTLC-based payment scheme (a.k.a. Lightning Network), a side-chain protocol and a cross-chain swap protocol

Analyse via la théorie des jeux sur les comportements des utilisateurs blockchain

The disruptive technology born in 2008 with Bitcoin and known as blockchain represents a significant quality leap from the distributed database technology. Distributed systems theory provides then models and techniques to analyze some protocols characterizing the technology, however in order to analyze a blockchain system additional considerations on its users need to be done. This thesis aims at analyzing the different behaviors of the users operating in blockchains or more in general in DLTs (i.e., Distributed Ledger Technologies).The latter are considered as rational agents, fully aware of all actions available to them and capable of choosing the one they feel is the best for themselves. Game theory is then used to model situations where users are called to choose and perform certain actions within the DLT environment. This thesis analyzes different users as well as different blockchains with the scope of providing a general overview on the topic and formal results on their behaviors ; users may indeed be honest vis-à-vis of other users or they may behave maliciously (as Byzantine nodes) attacking the blockchain system.La technologie disruptive née en 2008 avec Bitcoin et connue sous le nom de blockchain représente un saut qualitatif important par rapport à la technologie des bases de données distribuées. La théorie des systèmes distribués fournit alors des modèles et des techniques pour analyser certains protocoles caractérisant la technologie, cependant afin d’analyser un système blockchain des considérations supplémentaires sur ses utilisateurs doivent être faites. Cette thèse vise à analyser les différents comportements des utilisateurs opérant dans les blockchains ou plus largement dans les DLTs (i.e., Distributed Ledger Technologies). Ces derniers sont considérés comme des agents rationnels, pleinement conscients de toutes les actions à leur disposition et capables de choisir celle qui leur semble la meilleure pour eux-mêmes. La théorie des jeux est alors utilisée pour modéliser des situations o`u les utilisateurs sont appelés à choisir et à effectuer certaines actions dans l’environnement DLT. Cette thèse analyse différents utilisateurs ainsi que différentes blockchains dans le but de fournir une vue d’ensemble sur le sujet et des résultats formels sur leurs comportements ; les utilisateurs peuvent en effet être honnêtes vis-`a-vis des autres utilisateurs ou se comporter de manière malveillante (comme des noeuds byzantins) en attaquant le système blockchain

Analyse via la théorie des jeux sur les comportements des utilisateurs blockchain

The disruptive technology born in 2008 with Bitcoin and known as blockchain represents a significant quality leap from the distributed database technology. Distributed systems theory provides then models and techniques to analyze some protocols characterizing the technology, however in order to analyze a blockchain system additional considerations on its users need to be done. This thesis aims at analyzing the different behaviors of the users operating in blockchains or more in general in DLTs (i.e., Distributed Ledger Technologies).The latter are considered as rational agents, fully aware of all actions available to them and capable of choosing the one they feel is the best for themselves. Game theory is then used to model situations where users are called to choose and perform certain actions within the DLT environment. This thesis analyzes different users as well as different blockchains with the scope of providing a general overview on the topic and formal results on their behaviors ; users may indeed be honest vis-à-vis of other users or they may behave maliciously (as Byzantine nodes) attacking the blockchain system.La technologie disruptive née en 2008 avec Bitcoin et connue sous le nom de blockchain représente un saut qualitatif important par rapport à la technologie des bases de données distribuées. La théorie des systèmes distribués fournit alors des modèles et des techniques pour analyser certains protocoles caractérisant la technologie, cependant afin d’analyser un système blockchain des considérations supplémentaires sur ses utilisateurs doivent être faites. Cette thèse vise à analyser les différents comportements des utilisateurs opérant dans les blockchains ou plus largement dans les DLTs (i.e., Distributed Ledger Technologies). Ces derniers sont considérés comme des agents rationnels, pleinement conscients de toutes les actions à leur disposition et capables de choisir celle qui leur semble la meilleure pour eux-mêmes. La théorie des jeux est alors utilisée pour modéliser des situations o`u les utilisateurs sont appelés à choisir et à effectuer certaines actions dans l’environnement DLT. Cette thèse analyse différents utilisateurs ainsi que différentes blockchains dans le but de fournir une vue d’ensemble sur le sujet et des résultats formels sur leurs comportements ; les utilisateurs peuvent en effet être honnêtes vis-`a-vis des autres utilisateurs ou se comporter de manière malveillante (comme des noeuds byzantins) en attaquant le système blockchain

Analyse via la théorie des jeux sur les comportements des utilisateurs blockchain

La technologie disruptive née en 2008 avec Bitcoin et connue sous le nom de blockchain représente un saut qualitatif important par rapport à la technologie des bases de données distribuées. La théorie des systèmes distribués fournit alors des modèles et des techniques pour analyser certains protocoles caractérisant la technologie, cependant afin d’analyser un système blockchain des considérations supplémentaires sur ses utilisateurs doivent être faites. Cette thèse vise à analyser les différents comportements des utilisateurs opérant dans les blockchains ou plus largement dans les DLTs (i.e., Distributed Ledger Technologies). Ces derniers sont considérés comme des agents rationnels, pleinement conscients de toutes les actions à leur disposition et capables de choisir celle qui leur semble la meilleure pour eux-mêmes. La théorie des jeux est alors utilisée pour modéliser des situations o`u les utilisateurs sont appelés à choisir et à effectuer certaines actions dans l’environnement DLT. Cette thèse analyse différents utilisateurs ainsi que différentes blockchains dans le but de fournir une vue d’ensemble sur le sujet et des résultats formels sur leurs comportements ; les utilisateurs peuvent en effet être honnêtes vis-`a-vis des autres utilisateurs ou se comporter de manière malveillante (comme des noeuds byzantins) en attaquant le système blockchain.The disruptive technology born in 2008 with Bitcoin and known as blockchain represents a significant quality leap from the distributed database technology. Distributed systems theory provides then models and techniques to analyze some protocols characterizing the technology, however in order to analyze a blockchain system additional considerations on its users need to be done. This thesis aims at analyzing the different behaviors of the users operating in blockchains or more in general in DLTs (i.e., Distributed Ledger Technologies).The latter are considered as rational agents, fully aware of all actions available to them and capable of choosing the one they feel is the best for themselves. Game theory is then used to model situations where users are called to choose and perform certain actions within the DLT environment. This thesis analyzes different users as well as different blockchains with the scope of providing a general overview on the topic and formal results on their behaviors ; users may indeed be honest vis-à-vis of other users or they may behave maliciously (as Byzantine nodes) attacking the blockchain system

Analyse via la théorie des jeux sur les comportements des utilisateurs blockchain

The disruptive technology born in 2008 with Bitcoin and known as blockchain represents a significant quality leap from the distributed database technology. Distributed systems theory provides then models and techniques to analyze some protocols characterizing the technology, however in order to analyze a blockchain system additional considerations on its users need to be done. This thesis aims at analyzing the different behaviors of the users operating in blockchains or more in general in DLTs (i.e., Distributed Ledger Technologies).The latter are considered as rational agents, fully aware of all actions available to them and capable of choosing the one they feel is the best for themselves. Game theory is then used to model situations where users are called to choose and perform certain actions within the DLT environment. This thesis analyzes different users as well as different blockchains with the scope of providing a general overview on the topic and formal results on their behaviors ; users may indeed be honest vis-à-vis of other users or they may behave maliciously (as Byzantine nodes) attacking the blockchain system.La technologie disruptive née en 2008 avec Bitcoin et connue sous le nom de blockchain représente un saut qualitatif important par rapport à la technologie des bases de données distribuées. La théorie des systèmes distribués fournit alors des modèles et des techniques pour analyser certains protocoles caractérisant la technologie, cependant afin d’analyser un système blockchain des considérations supplémentaires sur ses utilisateurs doivent être faites. Cette thèse vise à analyser les différents comportements des utilisateurs opérant dans les blockchains ou plus largement dans les DLTs (i.e., Distributed Ledger Technologies). Ces derniers sont considérés comme des agents rationnels, pleinement conscients de toutes les actions à leur disposition et capables de choisir celle qui leur semble la meilleure pour eux-mêmes. La théorie des jeux est alors utilisée pour modéliser des situations o`u les utilisateurs sont appelés à choisir et à effectuer certaines actions dans l’environnement DLT. Cette thèse analyse différents utilisateurs ainsi que différentes blockchains dans le but de fournir une vue d’ensemble sur le sujet et des résultats formels sur leurs comportements ; les utilisateurs peuvent en effet être honnêtes vis-`a-vis des autres utilisateurs ou se comporter de manière malveillante (comme des noeuds byzantins) en attaquant le système blockchain

Rewarding miners: bankruptcy situations and pooling strategies

International audienceIn Proof-of-Work (PoW) based blockchains (e.g., Bitcoin), mining is the procedure through which miners can gain money on regular basis by finding solutions to mathematical crypto puzzles (i.e., full solutions) which validate blockchain transactions. In order to reduce the uncertainty of the remuneration over time, miners cooperate and form pools.Each pool receives rewards which have to be split among pool’s participants. The objective of this paper is to find an allocation method, for a mining pool, aimed at redistributing the rewards among cooperating miners and, at the same time, preventing some malicious behaviours of the miners.Recently, Schrijvers et al. (2017) have proposed a rewarding mechanism that is incentive compatible, ensuring that miners have an advantage to immediately report full solutions to the pool. However, such a mechanism encourages a harmful inter-pool behaviour (i.e., pool hopping) when the reward results insufficient to remunerate pool miners, determining a loss in terms of pool’s computational power.By reinterpreting the allocation rules as outcomes of bankruptcy situations, we define a new rewarding system based on the well-studied Constrained Equal Losses (CEL) rule that maintains the incentive compatible property while making pool hopping less advantageous

Bitcoin Pool-Hopping Detection

International audienceIn the Bitcoin blockchain, rewarding methods for remunerating miners participating in a pool have to meet certain requirements in order to guarantee the proper functioning of the cryptocurrency ecosystem. In particular, these allocation rules reward pool participants in proportion to their contribution in the transaction validation process. Deployed rewarding methods met fairness concerns at the expense of vulnerability to miners exploiting pools' attractiveness for deciding when to mine for a pool and when to 'hop' to another one resulting more attractive: a phenomenon called pool-hopping. The most used score-based methods are designed to prevent this practice, but are not completely hopping proof. In this work, we propose a methodology to analyze the pool-hopping phenomenon, focusing on the detection of pool-hoppers. Analyzing those Bitcoin transactions that pools create for rewarding its participants, it is possible to determine time epochs where miners worked. Thus, we analyze those miners that have worked intermittently for pools adopting a rewarding system which pays out for each validated block. This evaluation leads us qualifying the miners that have hopped along with their hopping behavior and financial performance

A Vademecum on Blockchain Technologies: When, Which and How

International audienceBlockchain is a technology making the shared registry concept from distributed systems a reality for a number of application domains, from the cryptocurrency one to potentially any industrial system requiring decentralized, robust, trusted and automated decision making in a multi-stakeholder situation. Nevertheless, the actual advantages in using blockchain instead of any other traditional solution (such as centralized databases) are not completely understood to date, or at least there is a strong need for a vademecum guiding designers toward the right decision about when to adopt blockchain or not, which kind of blockchain better meets use-case requirements, and how to deploy it. In this article we aim at providing the community with such a vademecum, while giving a general presentation of blockchain that goes beyond its usage in Bitcoin, surveying a selection of the vast literature that emerged in the last few years. We draw the key requirements and their evolution when passing from permissionless to permissioned blockchains, presenting the differences between proposed and experimented consensus mechanisms, and describing existing blockchain platforms

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