Lighthouse: an Ethereum 2.0 client

A work-in-progress, open-source implementation of the Ethereum 2.0 Beacon Chain, maintained by Sigma Prime.

Introduction

Lighthouse is an open-source Ethereum 2.0 client, in development. It is an Ethereum 2.0-only client, meaning it won't re-implement the present proof-of-work protocol. This will help it stay focussed on 2.0 without reproducing the work that other clients are already doing very well.

This readme is split into two major sections:

• Lighthouse Client: information about this implementation.
• What is Ethereum 2.0: an introduction to Ethereum 2.0.

If you'd like some background on Sigma Prime, please see the Lighthouse Update #00 blog post.

Lighthouse Client

Goals

We aim to contribute to the research and development of a secure, efficient and decentralised Ethereum protocol through the development of an open-source Ethereum 2.0 client.

We aim to provide a secure and efficient open-source client. As well as building an implementation, we seek to help maintain and improve the protocol wherever possible.

Components

Lighthouse is presently focussed on the Beacon Chain implementation. Here are some of the components actively under development by the team:

• BLS cryptography: we presently use the Apache Milagro cryptography library to create and verify BLS aggregate signatures. These signatures are core to Eth 2.0 and allow the signatures of many validators to be compressed into a constant 96 bytes and verified efficiently. We're presently maintaining our own BLS aggregates library, gratefully forked from @lovesh.
• DoS-resistant block pre-processing: processing blocks in proof-of-stake is more resource intensive than proof-of-work. As such, clients need to ensure that bad blocks can be rejected as efficiently as possible. We can presently process a block with 10 million ETH staked in 0.006 seconds and reject valid blocks even quicker. See the issue on ethereum/beacon_chain .
• P2P networking: Eth 2.0 is likely to use the libp2p framework, lighthouse hopes to work alongside Parity to get libp2p-rust fit-for-purpose.
• Validator duties : providing "validator" services to users who wish to stake ETH. This involves maintaining a consistent view of the chain and voting upon shard and beacon chain blocks.
• New serialization formats: lighthouse is working alongside the EF researchers to develop "simpleserialize" a purpose-built serialization format for sending information across the network. Check our our SSZ implementation and our research on serialization formats.
• Casper FFG fork-choice: the Casper FFG fork-choice rules allow the chain to select a canonical chain in the case of a fork.
• Efficient state transition logic: "state transition" logic deals with updating the validator set as validators log in/out, penalising/rewarding validators, rotating validators across shards, and many other core tasks.
• Fuzzing and testing environments: we are preparing to implement lab environments with CI work-flows to provide automated security analysis.

On top of these components we're also working on database schemas, RPC frameworks, specification development, database optimizations (e.g., bloom-filters) and tons of other interesting stuff (at least we think so).

Contributing

Lighthouse welcomes contributors with open-arms.

Layer-1 infrastructure is a critical component of the ecosystem and relies heavily on community contribution. Building Ethereum 2.0 is a huge task and we refuse to "do an ICO" or charge licensing fees. Instead, we fund development through grants and support from Sigma Prime.

If you would like to learn more about Ethereum 2.0 and/or Rust, we would be more than happy to on-board you and assign you to some tasks. We aim to be as accepting and understanding as possible; we are more than happy to up-skill contributors in exchange for their help on the project.

Alternatively, if you an ETH/Rust veteran we'd love to have your input. We're always looking for the best way to do things and will always consider any respectfully presented criticism.

If you'd like to contribute, try having a look through the open issues (tip: look for the good first issue tag) and ping us on the gitter. We need your support!

Running

NOTE: the cryptography libraries used in this implementation are experimental and as such all cryptography should be assumed to be insecure.

The code-base is still under-development and does not provide any user-facing functionality. However, there are a lot of tests and some benchmarks if that sort of thing interests you.

To run the tests, use

$ cargo test --all

To run benchmarks, use

$ cargo bench --all

Lighthouse presently runs on Rust stable, however benchmarks require the nightly version.

Engineering Ethos

Lighthouse aims to produce many small, easily-tested components, each separated into individual crates wherever possible.

Generally, tests can be kept in the same file, as is typical in Rust. Integration tests should be placed in the tests directory in the crates root. Particularity large (line-count) tests should be separated into another file.

A function is not complete until it is tested. We produce tests to help ourselves and others understand others code and to provide protection from regression (breaking stuff accidentally).

Each PR is to be reviewed by at-least one "core developer" (i.e., someone with write-access to the repository). This helps to detect bugs, improve consistency and relieves any one individual of the responsibility of an error.

Discussion should be respectful and intellectual. Have fun, make jokes but respect other people's limits.

Directory Structure

Here we provide an overview of the directory structure:

• \beacon_chain: contains logic derived directly from the specification. E.g., shuffling algorithms, state transition logic and structs, block validation, BLS crypto, etc.
• \lighthouse: contains logic specific to this client implementation. E.g., CLI parsing, RPC end-points, databases, etc.
• \network-libp2p: contains a proof-of-concept libp2p implementation. Will be replaced once research around p2p has been finalized.

Contact

The best place for discussion is the sigp/lighthouse gitter. Ping @paulhauner or @AgeManning to get the quickest response.

What is Ethereum 2.0

Ethereum 2.0 is the name that has been given to a new blockchain being developed by the Ethereum Foundation and the Ethereum community. Ethereum 2.0 consists of 1,025 proof-of-stake blockchains; the "beacon chain" and 1,024 "shard chains".

Beacon Chain

The Beacon Chain is a little different to more common blockchains like Bitcoin and present-Ethereum in that it doesn't process "transactions", per say. Instead, it maintains a set of bonded (staked) validators and co-ordinates them to provide services to a static set of "sub-blockchains" (shards). These shards then process the normal "5 ETH from A to B" transactions in parallel whilst deferring consensus to the Beacon Chain.

Here are some of the major services that the beacon chain provides to its shards:

• A source of entropy, likely using a RANDAO + VDF scheme.
• Validator management, including:
  • Inducting and ejecting validators.
  • Delegating randomly-shuffled subsets of validators to validate shards.
  • Penalising and rewarding validators.
• Proof-of-stake consensus for shard chain blocks.

Shard Chains

Shards can be thought of like CPU cores, they're a lane where transactions can execute in series (one-after-another). Presently, Ethereum is single-core and can only fully process one transaction at a time. Sharding allows multiple transactions to happen in parallel, greatly increasing the per-second transaction capacity of Ethereum.

Each shard is proof-of-stake and shares its validators (stakers) with the other shards as the beacon chain rotates validators pseudo-randomly across shards. Shards will likely be the basis of very interesting layer-2 transaction processing schemes, however we won't get into that here.

The Proof-of-Work Chain

The proof-of-work chain will hold a contract to allow addresses to deposit 32 ETH, a BLS public key and some other parameters to allow them to become Beacon Chain validators. Each Beacon Chain will reference a PoW block hash allowing PoW clients to use the Beacon Chain as a source of Casper FFG finality, if they desire.

Ethereum 2.0 Progress

Ethereum 2.0 is not fully specified and there's no working implementation. Some teams have demos available, however these demos indicate progress, not completion. We look forward to providing user functionality once we are ready to provide a minimum-viable user experience.

The work-in-progress specification lives here in the ethereum/eth2.0-specs repository. It is still in a draft phase, however there are several teams already implementing it. This spec is being developed by Ethereum Foundation researchers, most notably Vitalik Buterin. There is active discussion about the spec in the ethereum/sharding gitter channel. There is a proof-of-concept implementation in Python at ethereum/beacon_chain.

Presently, the spec almost exclusively defines the Beacon Chain as it is the focus of present development efforts. Progress on shard chain specification will soon follow.