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--- education [2022/02/25 11:01]
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   * **[[cryptocurrencies|Cryptocurrencies]]**: We have several project openings as part of our ongoing research on designing new cryptocurrency systems. Please contact [[rachid.guerraoui@epfl.ch|Prof. Rachid Guerraoui]].
-  * **On the design and implementation of scalable and secure blockchain algorithms**: Consensus has recently gained in popularity with the advent of blockchain technologies. Unfortunately, most blockchains do not scale due, in part, to their centralized (leader-based) limitation. We recently designed a promising fully decentralised (leader-less) algorithm that promises to scale to large networks. The goal of this project is to implement it in rust and compare its performance on AWS instances against a traditional leader-based alternative like BFT-Smart whose code will be provided. Contact [[https://people.epfl.ch/vincent.gramoli|Vincent Gramoli]] for more information.
-  * **Making Blockchain Accountable**: Abstract: One of the key drawback of blockchain is its lack of accountability. In fact, it does not hold participants responsible for their actions. This is easy to see as a malicious or Byzantine user typically double spends in a branch of blocks that disappears from the system, hence remaining undetected. Accountability is often thought to be communication costly: to detect a malicious participants who has sent deceitful messages to different honest participants for them to disagree, one may be tempted to force each honest participant to exchange all the messages they receive and cross-check them. However, we have recently designed an algorithm that shares the same communication complexity as the current consensus algorithms of existing blockchains. The goal of this project is to make blockchains accountable by implementing this accountable consensus algorithm and comparing it on a distributed set of machines against a baseline implementation. Contact [[https://people.epfl.ch/vincent.gramoli|Vincent Gramoli]] for more information.
+  * **Proof systems for Byzantine systems**: Cryptographic proof systems enable the rapid verification of computation between mutually distrustful parties. Recent advances in proof systems include (1) recursive proofs, transition proofs and accumulators which are of prime interest to shrink long chains of computation and/or their associated storage, and (2) zero-knowledge scalable proofs useful for privacy-preserving systems. Motivated by cryptocurrencies, the goal of this project is to devise and implement Byzantine-resilient systems that incorporate new cryptographic proof systems for efficiency and/or privacy. Contact Pierre-Louis Roman <pierre-louis.roman@epfl.ch> for more information.
+  * **Topology-aware mempool for cryptocurrencies**: The mempool is a core component of cryptocurrency systems. It disseminates user transactions to the miner nodes before they reach consensus.Current mempools assume an homogeneous network topology where all machines have the same bandwidth and latency.This unrealitic assumption forces the system to progress at the same speed as the slowest node in the system. This project aims at implementing a mempool which exploits the heterogeneity of the network to speed up data dissemination for cryptocurrency systems. This is a practical project which requires good knowledge in network programming, either Go or C++, distributed algorithms. Contact Gauthier Voron <gauthier.voron@epfl.ch> for more information.
   * **Robust mean estimation**: In recent years, many algorithms have been proposed to perform robust mean estimation, which has been shown to be equivalent to robust gradient-based machine learning. A new concept has been proposed to define the performance of a robust mean estimator, called the [[https://arxiv.org/abs/2008.00742|averaging constant]] (along with the Byzantine resilience). This research project consists of computing the theoretical averaging constant of different proposed robust mean estimators, and to study their empirical performances on randomly generated vectors. Contact [[https://people.epfl.ch/sadegh.farhadkhani?lang=en|Sadegh Farhadkhani]] for more information.
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   * **Accelerate Byzantine collaborative learning**: [[https://arxiv.org/abs/2008.00742|Our recent NeurIPS paper]] proposed algorithms for collaborative machine learning in the presence of Byzantine nodes, which have been proved to be near optimal with respect to optimality at convergence. However, these algorithms require all-to-all communication at every round, which is suboptimal. This research consists of designing a practical solution to Byzantine collaborative learning, based on the idea of a random communication network at each round, with both theoretical guarantees and practical implementation. Contact [[https://people.epfl.ch/sadegh.farhadkhani?lang=en|Sadegh Farhadkhani]] for more information.
-  * **Decentralize Tournesol’s learning algorithms**: The [[https://tournesol.app/|Tournesol platform]] leverages the contributions of its community of contributors to assign a « should be more recommended » score to YouTube videos rated by the contributors, using a learning algorithm. Currently, the computations are performed on a central server. But as Tournesol’s user base grows, and as more sophisticated learning algorithms are considered for deployment, there is a growing need to decentralize the computations of the learning algorithm. This project aims to build a framework, which will enable Tournesol users to run part of the computations of Tournesol’s scores directly in their browsers. Contact [[https://people.epfl.ch/le.hoang/?lang=en|Lê Nguyên Hoang]] for more information.
-  * **Listening to the silent majority**: Vanilla machine learning from user-generated data inevitably favors those who generated the most amounts of data. But this means that learning algorithms will be optimized for these users, rather than for the silent majority. This research aims to correct for this bias, by trying to infer what data the majority would have likely generated, and by inferring what the models would have learned if the silent majority’s data was included in the training of the models. It involves both designing algorithms, proving correctness and implementing them. This research is motivated by the [[https://tournesol.app/|Tournesol project]]. Contact [[https://people.epfl.ch/le.hoang/?lang=en|Lê Nguyên Hoang]] for more information.
-  * **Should experts be given more voting rights?**: This is a question that Condorcet tackled in 1785, through what is now known as the jury problem. However, his model was crude and does not apply to many critical problems, e.g. determining if a video on vaccines should be largely recommended. This research aims to better understand how voting rights should be allocated, based not only on how likely voters are to be correct, but also on the correlations between the voters’ judgments. So far, it involves mostly a theoretical analysis. This research is motivated by the [[https://tournesol.app/|Tournesol project]]. Contact [[https://people.epfl.ch/le.hoang/?lang=en|Lê Nguyên Hoang]] for more information.
   * **Probabilistic Byzantine Resilience**:  Development of high-performance, Byzantine-resilient distributed systems with provable probabilistic guarantees. Two options are currently available, both building on previous work on probabilistic Byzantine broadcast: (i) a theoretical project, focused the correctness of probabilistic Byzantine-tolerant distributed algorithms; (ii) a practical project, focused on numerically evaluating of our theoretical results. Please contact [[matteo.monti@epfl.ch|Matteo Monti]] to get more information.
-  * **Distributed coordination using RDMA.** RDMA (Remote Direct Memory Access) allows accessing a remote machine's memory without interrupting its CPU. This technology is gaining traction over the last couple of years, as it allows for the creation of real-time distributed systems. RDMA allows for communication to take place close to the μsec scale, which enables the design and implementation of systems that process requests in only tens of μsec. Current research focuses on achieving real-time failure detection through a combination of novel algorithm design, latest hardware and linux kernel customization. Fast failure detection over RDMA brings the notion of availability to a new level, essentially allowing modern systems to enter the era of 7 nines of availability. Contact [[https://people.epfl.ch/athanasios.xygkis|Athanasios Xygkis]] and [[https://people.epfl.ch/antoine.murat|Antoine Murat]] for more information.
+  * **Microsecond-scale dependable systems.** Modern networking technologies such as RDMA (Remote Direct Memory Access) allow for sub-microsecond communication latency. Combined with emerging data center architectures, such as disaggregated resources pools, they open the door to novel blazing-fast and resource-efficient systems. Our research focuses on designing such microsecond-scale systems that can also tolerate faults. Our vision is that tolerating network asynchrony as well as faults (crash and/or Byzantine) is a must, but that it shouldn't affect the overall performance of a system. We achieve this goal by devising and implementing novel algorithms tailored for new hardware and revisiting theoretical models to better reflect modern data centers. Previous work encompasses microsecond-scale (BFT) State Machine Replication, Group Membership Services and Key-Value Stores (OSDI'20, ATC'22 and ASPLOS'23). Overall, if you are interested in making data centers faster and safer, contact [[https://people.epfl.ch/athanasios.xygkis|Athanasios Xygkis]] and [[https://people.epfl.ch/antoine.murat|Antoine Murat]] for more information.
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-  * **Hijacking proof-of-work to make it useful: distributed gradient-free learning approach**: Proof-of-work blockchains - notably Bitcoin and Ethereum - reach a probabilistic consensus about the contents of the blockchain by a mechanism of probabilistic leader election. Every contributor to the consensus tries to solve a puzzle, and the first one to succeed is elected a leader, allowed to create the next block and publicly add information to it. The puzzle needs to be hard to solve and easy to verify, solvable only by random guessing and not allowing for any shortcuts and allow for its difficulty to be tuned so that nodes don't find answers to it simultaneously and take different leaderships forking the chain in two. Partial cryptographic hash reversal has traditionally been a perfect candidate for such puzzle, but it has no interest outside being a challenge for blockchain. And with 100-300 PetaFLOP/s (drawing 100 TWh/y) of general purpose computational power being tied into Ethereum blockchain alone as of early 2022, the waste of computational resources and energy is colossal. While the interest of blockchains and the suitability of proof-of-work as a mechanism to run them is widely debated, it's at this day the mechanism for the two largest ones. We try to at least use some of that challenge useful by injecting a "try" step of a (1,λ)-ES evolutionary search algorithm into the hash computation loop, slowing it down and making it do something useful in during the slowdown period. This class of evolutionary search algorithm achieves a good performance on black-bock optimization tasks (sometimes exceeding RL approaches in traditionally RL problems), is embarrassingly parallel, fits well the requirements for a proof-of-work function and can be empirically optimized to minimize the waste of computational resources during a training run.
+  * **Hijacking proof-of-work to make it useful: distributed gradient-free learning approach**: Proof-of-work blockchains - notably Bitcoin and Ethereum - reach a probabilistic consensus about the contents of the blockchain by a mechanism of probabilistic leader election. Every contributor to the consensus tries to solve a puzzle, and the first one to succeed is elected a leader, allowed to create the next block and publicly add information to it. The puzzle needs to be hard to solve and easy to verify, solvable only by random guessing and not allowing for any shortcuts and allow for its difficulty to be tuned so that nodes don't find answers to it simultaneously and take different leaderships forking the chain in two. Partial cryptographic hash reversal has traditionally been a perfect candidate for such puzzle, but it has no interest outside being a challenge for blockchain. And with 100-300 PetaFLOP/s (drawing 100 TWh/y) of general purpose computational power being tied into Ethereum blockchain alone as of early 2022, the waste of computational resources and energy is colossal. While the interest of blockchains and the suitability of proof-of-work as a mechanism to run them is widely debated, it's at this day the mechanism for the two largest ones. We try to at least use some of that challenge useful by injecting a "try" step of a (1,λ)-ES evolutionary search algorithm into the hash computation loop, slowing it down and making it do something useful in during the slowdown period. This class of evolutionary search algorithm achieves a good performance on black-bock optimization tasks (sometimes exceeding RL approaches in traditionally RL problems), is embarrassingly parallel, fits well the requirements for a proof-of-work function and can be empirically optimized to minimize the waste of computational resources during a training run. However, in its current state the (1,λ)-ES-based useful proof-of-work has been proven to work in cases where the data used for the training tasks can be fully replicated among the nodes. For numerous applications, it is not an option. Finding ways to solve that problem, both from a theoretical and an experimental perspective will be the goal of this project. You will need solid skills in Python (Rust and WebAssembly are a plus), basic understanding of distributed algorithms and of machine learning concepts. Some familiarity with blockchains and black box optimization is a plus, but is not a requirement. Contact [[https://people.epfl.ch/andrei.kucharavy|Andrei Kucharavy]] for more information.
-However, in its current state the (1,λ)-ES-based useful proof-of-work has been proven to work in cases where the data used for the training tasks can be fully replicated among the nodes. For numerous applications, it is not an option. Finding ways to solve that problem, both from a theoretical and an experimental perspective will be the goal of this project.
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-You will need solid skills in Python (Rust and WebAssembly are a plus), basic understanding of distributed algorithms and of machine learning concepts. Some familiarity with blockchains and black box optimization is a plus, but is not a requirement. Contact Andrei Kucharavy (andrei.kucharavy@epfl.ch) for more information.
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