Publications de Vincent Gramoli

Blockchain Double Spending with Low Mining Power and Network Delays

Traditional blockchain systems offer a secure way of tracking the ownership of digital assets as long as the attacker does not control a large portion of the overall computational or mining power. They typically require participants to generate a proof-of- ...

2024

Byzantine consensus is Θ(n^2): the Dolev-Reischuk bound is tight even in partial synchrony!

Rachid Guerraoui, Seth Gilbert, Vincent Gramoli, Manuel José Ribeiro Vidigueira, Jovan Komatovic, Pierre Philippe Civit

The Dolev-Reischuk bound says that any deterministic Byzantine consensus protocol has (at least) quadratic (in the number of processes) communication complexity in the worst case: given a system with n processes and at most f < n/3 failures, any solution t ...

2023

As easy as ABC: Optimal (A)ccountable (B)yzantine (C)onsensus is easy!

Rachid Guerraoui, Seth Gilbert, Vincent Gramoli, Jovan Komatovic, Pierre Philippe Civit

In a non-synchronous system with n processes, no t(0)-resilient (deterministic or probabilistic) Byzantine consensus protocol can prevent a disagreement among correct processes if the number of faulty processes is > n - 2t(0). Therefore, the community defi ...

ACADEMIC PRESS INC ELSEVIER SCIENCE2023

Leaderless consensus

Rachid Guerraoui, Vincent Gramoli, Mihail Igor Zablotchi, Karolos Antoniadis, Antoine Philippe Matthieu Desjardins, Gauthier Jérôme Timothée Voron

Classic synchronous consensus algorithms are leaderless in that processes exchange proposals, choose the maximum value and decide when they see the same choice across a couple of rounds. Indulgent consensus algorithms are typically leader-based. Although t ...

ACADEMIC PRESS INC ELSEVIER SCIENCE2023

DIABLO: A Benchmark Suite for Blockchains

Rachid Guerraoui, Vincent Gramoli, Andrei Lebedev, Gauthier Jérôme Timothée Voron

With the recent advent of blockchains, we have witnessed a plethora of blockchain proposals. These proposals range from using work to using time, storage or stake in order to select blocks to be appended to the chain. As a drawback it makes it difficult fo ...

ASSOC COMPUTING MACHINERY2023

Cross-chain payment protocols with success guarantees

Vincent Gramoli

In this paper, we consider the problem of cross-chain payment whereby customers of different escrows-implemented by a bank or a blockchain smart contract-successfully transfer digital assets without trusting each other. Prior to this work, cross-chain paym ...

SPRINGER2023

As easy as ABC: Optimal (A)ccountable (B)yzantine (C)onsensus is easy!

Rachid Guerraoui, Seth Gilbert, Vincent Gramoli, Jovan Komatovic, Pierre Philippe Civit

It is known that the agreement property of the Byzantine consensus problem among n processes can be violated in a non-synchronous system if the number of faulty processes exceeds t0 = ┌n/3┐ − 1 [10], [19]. In this paper, we investigate the accountable Byza ...

IEEE2022

Crime and Punishment in Distributed Byzantine Decision Tasks

Rachid Guerraoui, Zarko Milosevic, Seth Gilbert, Vincent Gramoli, Jovan Komatovic, Pierre Philippe Civit

A decision task is a distributed input-output problem in which each process starts with its input value and eventually produces its output value. Examples of such decision tasks are broad and range from consensus to reliable broadcast to lattice agreement. ...

IEEE COMPUTER SOC2022

Byzantine Consensus is Θ(n^2): The Dolev-Reischuk Bound is Tight even in Partial Synchrony!

Rachid Guerraoui, Seth Gilbert, Vincent Gramoli, Manuel José Ribeiro Vidigueira, Jovan Komatovic, Pierre Philippe Civit

The Dolev-Reischuk bound says that any deterministic Byzantine consensus protocol has (at least) quadratic communication complexity in the worst case. While it has been shown that the bound is tight in synchronous environments, it is still unknown whether ...

Dagstuhl Publishing2022

Federated Learning Over Wireless Networks: Convergence Analysis and Resource Allocation

Vincent Gramoli

There is an increasing interest in a fast-growing machine learning technique called Federated Learning (FL), in which the model training is distributed over mobile user equipment (UEs), exploiting UEs' local computation and training data. Despite its advan ...

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC2021

Leaderless Consensus

Rachid Guerraoui, Vincent Gramoli, Mihail Igor Zablotchi, Karolos Antoniadis, Antoine Philippe Matthieu Desjardins

Classical synchronous consensus algorithms are leaderless: processes exchange their proposals, retain the maximum value and decide when they see the same choice across a couple of rounds. Indulgent consensus algorithms are more robust in that they only req ...

IEEE COMPUTER SOC2021

Rational Agreement in the Presence of Crash Faults

Vincent Gramoli, Alejandro Ranchal Pedrosa

Blockchain systems need to solve consensus despite the presence of rational users and failures. The notion of (k, t)-robustness is key to derive impossibility results with k rational players and t faulty players. However, these t faulty players are always ...

IEEE2021

The Performance of Byzantine Fault Tolerant Blockchains

Vincent Gramoli

Blockchains have captured the attention of many, resulting in an abundance of new systems available for use. However, selecting an appropriate blockchain for an application is challenging due to the lack of comparative information discussing core metrics s ...

IEEE2020

TM 2 C: a software transactional memory for many-cores

Rachid Guerraoui, Vincent Gramoli, Vasileios Trigonakis

2018

Elastic transactions

Pascal Felber, Rachid Guerraoui, Vincent Gramoli

This paper presents elastic transactions, an appealing alternative to traditional transactions, in particular to implement search structures in shared memory multicore architectures. Upon conflict detection, an elastic transaction might drop what it did so ...

Academic Press Inc Elsevier Science2017

Special issue on NETYS selected papers

Rachid Guerraoui, Vincent Gramoli

Springer Wien2015

Democratizing Transactional Programming

Rachid Guerraoui, Vincent Gramoli

Association for Computing Machinery2014

Composing Relaxed Transactions

Rachid Guerraoui, Vincent Gramoli, Mihai Letia

As the classic transactional abstraction is sometimes considered too restrictive in leveraging parallelism, a lot of work has been devoted to devising relaxed transactional models with the goal of improving concurrency. Nevertheless, the quest for improvin ...

IEEE Computer Society2013

A Speculation-Friendly Binary Search Tree

Vincent Gramoli

We introduce the first binary search tree algorithm designed for speculative executions. Prior to this work, tree structures were mainly designed for their pessimistic (non-speculative) accesses to have a bounded complexity. Researchers tried to evaluate t ...

Assoc Computing Machinery2012

Why STM can be more than a Research Toy

Pascal Felber, Rachid Guerraoui, Aleksandar Dragojevic, Vincent Gramoli

Software Transactional Memory (STM) promises to simplify concurrent programming without requiring specific hardware support. Yet, STM’s credibility lies on the extent to which it enables to leverage multicores and outperform sequential code. A recent CACM ...

2011