# Ethereum Protocol Fellowship Cohort 4 Recap

**TL;DR: The EPF concluded the fourth cohort and is preparing for a fifth cohort. Applications will be open soon. In the meantime, explore the new [EPF.wiki](http://epf.wiki/eps) and [sign up](https://groups.google.com/a/ethereum.org/g/protocol-fellowship-group) to get notified when they open.**

The Ethereum Protocol Fellowship recently completed its fourth successful cohort, culminating with EPF Day at Devconnect in Istanbul. Its completion marked 4 months of immersive learning, research and contribution to the Ethereum core ecosystem from a group of talented and dedicated fellows. To learn more about EPF, take a look at some of the [past posts](https://blog.ethereum.org/2023/05/10/ethereum-protocol-fellowship-third-recap) and [repos](https://github.com/eth-protocol-fellows).

### EPF4 Stats
Applications for the fourth cohort opened on June 2nd, 2023. After reviewing over 400 applications, 35 participants were awarded a stipend. Additionally, 5 retroactive stipends were awarded to permissionless participants. During the 4-month period, fellows had the opportunity to work with 27 core developer mentors from various client and research teams within the ecosystem. Their work was regularly reported in almost 600 weekly updates.

### EPF4 Projects
Altogether, fellows proposed and contributed to 35 projects, some of which are still active. These projects not only represent a valuable learning experience but also meaningful contributions to the Ethereum ecosystem.

| Project | Description |
| -------- | -------- |
| [Consensus Client in Elixir](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/LambdaClass-Ethereum-Elixir-Consensus-Client.md) | New open-source CL client written in Elixir created by Lambdaclass |
| [Verkle Implementation in Nim](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/verkle-tree-nim.md) | Contributions to verkle tree implementation in Nimbus |
| [JSON RPC - REST Wrapper](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/JSON_RPC_wrapper.md) | Middleware application enabling access to JSON-RPC via REST |
| [Node Crawler](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/node-crawler.md) | Refactoring, adding features, frontend and maintaining EL crawler |
| [PEP-C Boost PoC](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/pepc-boost.md) | PEP-C Boost proof of concept on Goerli |
| [Portal Network Validator](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/portal-network-validator.md) | Research to enable validators to run a Portal network client |
| [Verkle in Circuit](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/verkle-tries-in-circuit.md) | Benchmarks Pedersen and Keccak hashes in ZK circuits |
| [Lighthouse Slasher and Beacon Node Backend](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/lighthouse-slasher-and-beacon-node-backend.md) | Adds support for additional database backends in Lighthouse |
| [Prysm ePBS Support](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/epbs-with-inclusion-list.md) | Proof of concept for ePBS implementation in Prysm |
| [Eth Deb Packages](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/eth-deb-repository.md) | Creates reproducible builds and automatic configuration of nodes on Debian systems |
| [Optimal ZK Prover Mechanisms](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/prover-mechanism-in-zk-rollups.md) | Analysis and simulation of the mechanisms governing zk-rollup provers |
| [EOF Implementation in ETK](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/etk-eof-implementation.md) | Implements EOF in EVM Toolkit |
| [Nimbus Contributions](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/nimbus-consensus-client-enhancements.md) | Implements a novel append-only database for the Nimbus beacon node |
| [EIP-7212 in Reth](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/Reth_contributor.md) | Implements EIP-7212 in Reth |
| [Lighthouse Attestation Packing](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/attestation-aggregation-and-packing-optimisation-lighthouse.md) | Optimises attestation aggregtion in Lighthouse |
| [Post-Verkle State Expiry](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/post-verkle-state-expiry.md) | Introduces a new state expiry scheme that utilizes the Verkle Tree |
| [Ephemery Testnet Implementations](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/Ephemery-genesis-Lighthouse-Reth.MD) | Native Ephemery integration for Lodestar and Lighthouse |
| [Adding Lighthouse Metrics](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/improve-metrics-and-performance-lighthouse.md) | Exposes missed block and staking metrics |
| [Glados Improvements](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/Glados-PortalNetwork.md) | Monitors and visualises the health of the Portal Network |
| [Single Slot Finality Research](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/SSF-overview.md) | Academic overview of the SSF research and upgrades to consensus layer |
| [Stateless Account Abstraction](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/EIP-x-Efficient%20Light%20Client%20for%20Stateless%20Verification.md) | Stateless light client that consumes ZK proofs |
| [Poseidon Hash Cost Analysis](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/Computational_Cost_Analysis_of_Poseidon_Hash_as_an_EVM_Precompile.md) | Implements and benchmarks potential Poseidon precompile |
| [FHE-DKSAP](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/FHE-DKSAP.md) | Stealth address protocol with Fully Homomorphic Encryption |
| [Fuzzing the EVM](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/fuzzing-ethereum-network.md) | Enhances existing fuzzers based on Geth |
| [Optimism Sequencer Support](https://github.com/eth-protocol-fellows/cohort-four/blob/master/projects/Optimism-Sequencer-Support-for-ERC-4337-Bundlers.md) | Adds support for ERC-4337 bundlers in Optimism |

All resources of the program can be found in the [EPF4 repository](https://github.com/eth-protocol-fellows/cohort-four). You can follow all activity in the cohort there, checkout projects resources, development updates and fellows' notes. Projects are not only FOSS contributions but all of the work done within the cohort is fully open, being an actual part of Ethereum's open research and resources.

But it's not all about work and contributions. One of the crucial aspects of the EPF is the opportunity to meet many of the inspirational people who participate in core development. During Devconnect in Istanbul, over half of the cohort gathered to participate in EPF Day, a full day of programming with [project presentations](https://streameth.org/archive?event=epf_day), panel discussions and social time.

### Ethereum Protocol Fellowship Study Group
We learned some important feedback at the end of cohort 4. Despite the focus on protocol development education during EPF, the learning curve for aspiring core developers is still very steep. Based on this feedback, we started a pre-cursor program to the EPF called the [EPF study group](https://blog.ethereum.org/2024/02/07/epf-study-group), a 10-week deep dive into the various aspects of the protocol as well as a collaborative knowledge base for developers at [epf.wiki](https://epf.wiki/eps). EPF.wiki has become the place for aspiring core developers to learn about the technical aspects of Ethereum and contribute to the wiki to reinforce their knowledge.

### Next Cohort Soon™️
As the study group is coming to an end, we are gearing up for the fifth cohort of the Ethereum Protocol Fellowship. For anyone interested in diving into Ethereum core development, stay tuned for the application announcement in early May. To get notified, join the EPF [mailing list](https://groups.google.com/a/ethereum.org/g/protocol-fellowship-group).

Meanwhile, you can prepare your application by ensuring a foundational understanding of the Ethereum protocol (the EPF study group is a great place to start), contributing to open-source projects through your GitHub account, especially contributions to existing projects in the Ethereum ecosystem, and giving some thought to the type of project you may like to work on.