# Ethereum 2.0 Specifications

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To learn more about sharding and Ethereum 2.0 (Serenity), see the [sharding FAQ](https://github.com/ethereum/wiki/wiki/Sharding-FAQ) and the [research compendium](https://notes.ethereum.org/s/H1PGqDhpm).

This repository hosts the current Eth2 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

Core specifications for Eth2 clients be found in [specs/](specs/). These are divided into phases. Each subsequent phase depends upon the prior. The current phases specified are:

### Phase 0
* [The Beacon Chain](specs/phase0/beacon-chain.md)
* [Fork Choice](specs/phase0/fork-choice.md)
* [Deposit Contract](specs/phase0/deposit-contract.md)
* [Honest Validator](specs/phase0/validator.md)

### Phase 1
* [Custody Game](specs/phase1/custody-game.md)
* [Shard Data Chains](specs/phase1/shard-data-chains.md)
* [Misc beacon chain updates](specs/phase1/beacon-chain-misc.md)
* [Light client syncing protocol](specs/phase1/light-client-sync.md)

### Phase 2

Phase 2 is still actively in R&D and does not yet have any formal specifications.

See the [Eth2 Phase 2 Wiki](https://hackmd.io/UzysWse1Th240HELswKqVA?view) for current progress, discussions, and definitions regarding this work.

### 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:

* [Eth2 APIs](https://github.com/ethereum/eth2.0-apis)
* [Eth2 Metrics](https://github.com/ethereum/eth2.0-metrics/)
* [Interop Standards in Eth2 PM](https://github.com/ethereum/eth2.0-pm/tree/master/interop)

## Design goals

The following are the broad design goals for Ethereum 2.0:
* 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)


## 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)