# 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)

### Merge

The merge 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](https://ethresear.ch/t/the-eth1-eth2-transition/6265)
  * [ethereum.org](https://ethereum.org) high-level description of the merge [here](https://ethereum.org/en/eth2/docking/)
* Specifications:
  * [Beacon Chain changes](specs/merge/beacon-chain.md)
  * [Merge fork](specs/merge/fork.md)
  * [Fork Choice changes](specs/merge/fork-choice.md)
  * [Validator additions](specs/merge/validator.md)

### Sharding

Sharding follows the merge, 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).