# Ethereum Proof-of-Stake Consensus Specifications

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To learn more about proof-of-stake and sharding, see the [PoS FAQ](https://eth.wiki/en/concepts/proof-of-stake-faqs), [sharding FAQ](https://eth.wiki/sharding/Sharding-FAQs) and the [research compendium](https://notes.ethereum.org/s/H1PGqDhpm).

This repository hosts the current Ethereum proof-of-stake specifications. Discussions about design rationale and proposed changes can be brought up and discussed as issues. Solidified, agreed-upon changes to the spec can be made through pull requests.


## Specs

[![GitHub release](https://img.shields.io/github/v/release/ethereum/eth2.0-specs)](https://github.com/ethereum/eth2.0-specs/releases/) [![PyPI version](https://badge.fury.io/py/eth2spec.svg)](https://badge.fury.io/py/eth2spec)

Core specifications for Ethereum proof-of-stake clients can be found in [specs](specs/). These are divided into features.
Features are researched and developed in parallel, and then consolidated into sequential upgrades when ready.

The current features are:

### Phase 0

* [The Beacon Chain](specs/phase0/beacon-chain.md)
* [Beacon Chain Fork Choice](specs/phase0/fork-choice.md)
* [Deposit Contract](specs/phase0/deposit-contract.md)
* [Honest Validator](specs/phase0/validator.md)
* [P2P Networking](specs/phase0/p2p-interface.md)
* [Weak Subjectivity](specs/phase0/weak-subjectivity.md)

### Altair

* [Beacon chain changes](specs/altair/beacon-chain.md)
* [Altair fork](specs/altair/fork.md)
* [Light client sync protocol](specs/altair/sync-protocol.md)
* [Honest Validator guide changes](specs/altair/validator.md)
* [P2P Networking](specs/altair/p2p-interface.md)

### Bellatrix (also known as The Merge)

The Bellatrix protocol upgrade is still actively in development. The exact specification has not been formally accepted as final and details are still subject to change.

* Background material:
  * An [ethresear.ch](https://ethresear.ch) post [describing the basic mechanism of the CL+EL merge](https://ethresear.ch/t/the-eth1-eth2-transition/6265)
  * [ethereum.org](https://ethereum.org) high-level description of the CL+EL merge [here](https://ethereum.org/en/eth2/docking/)
* Specifications:
  * [Beacon Chain changes](specs/bellatrix/beacon-chain.md)
  * [Bellatrix fork](specs/bellatrix/fork.md)
  * [Fork Choice changes](specs/bellatrix/fork-choice.md)
  * [Validator additions](specs/bellatrix/validator.md)
  * [Client settings](specs/bellatrix/client-settings.md)
  * [P2P Networking](specs/bellatrix/p2p-interface.md)

### Sharding

Sharding follows Bellatrix, and is divided into three parts:

* Sharding base functionality - In early engineering phase
  * [Beacon Chain changes](specs/sharding/beacon-chain.md)
  * [P2P Network changes](specs/sharding/p2p-interface.md)
* Custody Game - Ready, dependent on sharding
  * [Beacon Chain changes](specs/custody_game/beacon-chain.md)
  * [Validator custody work](specs/custody_game/validator.md)
* Data Availability Sampling - In active R&D
  * Technical details [here](https://hackmd.io/@HWeNw8hNRimMm2m2GH56Cw/B1YJPGkpD).
  * [Core types and functions](specs/das/das-core.md)
  * [P2P Networking](specs/das/p2p-interface.md)
  * [Fork Choice](specs/das/fork-choice.md)
  * [Sampling process](specs/das/sampling.md)

### Accompanying documents can be found in [specs](specs) and include:

* [SimpleSerialize (SSZ) spec](ssz/simple-serialize.md)
* [Merkle proof formats](ssz/merkle-proofs.md)
* [General test format](tests/formats/README.md)

## Additional specifications for client implementers

Additional specifications and standards outside of requisite client functionality can be found in the following repos:

* [Beacon APIs](https://github.com/ethereum/beacon-apis)
* [Beacon Metrics](https://github.com/ethereum/beacon-metrics/)

## Design goals

The following are the broad design goals for the Ethereum proof-of-stake consensus specifications:
* to minimize complexity, even at the cost of some losses in efficiency
* to remain live through major network partitions and when very large portions of nodes go offline
* to select all components such that they are either quantum secure or can be easily swapped out for quantum secure counterparts when available
* to utilize crypto and design techniques that allow for a large participation of validators in total and per unit time
* to allow for a typical consumer laptop with `O(C)` resources to process/validate `O(1)` shards (including any system level validation such as the beacon chain)

## Useful external resources

* [Design Rationale](https://notes.ethereum.org/s/rkhCgQteN#)
* [Phase 0 Onboarding Document](https://notes.ethereum.org/s/Bkn3zpwxB)
* [Combining GHOST and Casper paper](https://arxiv.org/abs/2003.03052)

## For spec contributors

Documentation on the different components used during spec writing can be found here:
* [YAML Test Generators](tests/generators/README.md)
* [Executable Python Spec, with Py-tests](tests/core/pyspec/README.md)

## Consensus spec tests

Conformance tests built from the executable python spec are available in the [Ethereum Proof-of-Stake Consensus Spec Tests](https://github.com/ethereum/consensus-spec-tests) repo. Compressed tarballs are available in [releases](https://github.com/ethereum/consensus-spec-tests/releases).