fjrojasgarcia / prysm

Go implementation of Ethereum 2.0 - casper & sharding

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Prysmatic Labs Ethereum 2.0 Implementation

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This is the main repository for the beacon chain and sharding implementation for Ethereum 2.0 Prysmatic Labs.

Before you begin, check out our Contribution Guidelines and join our active chat room on Discord or Gitter below:

Discord Gitter

Also, read our Sharding Reference Implementation Doc. This doc provides a background on the sharding implementation we follow at Prysmatic Labs.

Table of Contents


Create a folder in your $GOPATH and navigate to it

mkdir -p $GOPATH/src/ && cd $GOPATH/src/

Note: it is not necessary to clone to the gopath if you're only building with Bazel.

Clone our repository:

git clone

Download the Bazel build tool by Google here and ensure it works by typing

bazel version

Bazel manages all of the dependencies for you (including go and necessary compilers) so you are all set to build prysm.

Sharding Instructions

To get started with running the project, follow the instructions to initialize your own private Ethereum blockchain and geth node, as they will be required to run before you can begin running our system

Running a Local Geth Node

To start a local Geth node, you can create your own genesis.json file similar to:

    "config": {
        "chainId": 12345,
        "homesteadBlock": 0,
        "eip155Block": 0,
        "eip158Block": 0
    "difficulty": "200",
    "gasLimit": "210000000000",
    "alloc": {
        "826f3F66dB0416ea82033aE917A611bfBF4D98b6": { "balance": "300000" }

The alloc portion specifies account addresses with prefunded ETH when the Ethereum blockchain is created. You can modify this section of the genesis to include your own test address and prefund it with 100ETH.

Then, you can build and init a new instance of a local, Ethereum blockchain as follows:

$ geth init /path/to/genesis.json -datadir /path/to/your/datadir
$ geth --nodiscover console --datadir /path/to/your/datadir --networkid 12345

It is important to note that the --networkid flag must match the chainId property in the genesis file.

Then, the geth console can start up and you can start a miner as follows:

> personal.newAccount()
> miner.setEtherbase(eth.accounts[0])
> miner.start(1)

Now, save the passphrase you used in the geth node into a text file called password.txt. Then, once you have this private geth node running on your local network, we will need to generate test, pending transactions that can then be processed into collations by proposers. For this, we have created an in-house transaction generator CLI tool.

Sharding Minimal Protocol

NOTE: This section is in flux: will be deprecated in favor of a beacon chain)

Build our system first

$ bazel build //client/...

Becoming a Attester

Make sure a geth node is running as a separate process. Then, to deposit ETH and join as a attester in the Sharding Manager Contract, run the following command:

bazel run //client -- \
   --actor "attester" \
   --deposit \
   --datadir /path/to/your/datadir \
   --password /path/to/your/password.txt \
   --networkid 12345

This will extract 1000ETH from your account balance and insert you into the SMC's attesters. Then, the program will listen for incoming block headers and notify you when you have been selected as to vote on proposals for a certain shard in a given period. Once you are selected, your sharding node will download collation information to check for data availability on vote on proposals that have been submitted via the addHeader function on the SMC.

Concurrently, you will need to run another service that is tasked with processing transactions into collations and submitting them to the SMC via the addHeader function.

Running a Collation Proposal Node

bazel run //client -- \
   --actor "proposer" \
   --datadir /path/to/your/datadir \
   --password /path/to/your/password.txt \
   --shardid 0 \
   --networkid 12345

This node is tasked with processing pending transactions into blobs within collations by serializing data into collation bodies. It is responsible for submitting proposals on shard 0 (collation headers) to the SMC via the addHeader function.

Running via Docker

To run the client within a docker container, use the //client:image target.

bazel run //client:image

INFO: Build options have changed, discarding analysis cache.
INFO: Analysed target //client:image (306 packages loaded).
INFO: Found 1 target...
Target //client:image up-to-date:
INFO: Elapsed time: 8.568s, Critical Path: 0.22s
INFO: 0 processes.
INFO: Build completed successfully, 1 total action
INFO: Build completed successfully, 1 total action
37fd88e7190b: Loading layer  22.42MB/22.42MB
Loaded image ID: sha256:89b233de1a026eddeeff010fa1ef596ce791cb3f26488150aac72a91b80734c1
Tagging 89b233de1a026eddeeff010fa1ef596ce791cb3f26488150aac72a91b80734c1 as bazel/client:image

TODO: Add container_push targets for the container images such that they can be pulled from GCR or dockerhub.

Making Changes

Rebuilding the Sharding Manager Contract Bindings

The Sharding Manager Contract is built in Solidity and deployed to a running geth node upon launch of the sharding node if it does not exist in the network at a specified address. If there are any changes to the SMC's code, the Golang bindigs must be rebuilt with the following command.

go generate
# OR
cd client/contracts && go generate


To run the unit tests of our system do:

$ bazel test //...

To run our linter, make sure you have gometalinter installed and then run

$ gometalinter ./...


We have put all of our contribution guidelines into! Check it out to get started.



GNU General Public License v3.0

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Go implementation of Ethereum 2.0 - casper & sharding

License:GNU General Public License v3.0


Language:Go 86.7%Language:Python 10.6%Language:Solidity 2.4%Language:Shell 0.3%