coincoin is a cryptocurrency proof-of-concept implemented in Elixir. It's an umbrella project that focuses on the 2 main components of (most of) the existing cryptocurrencies: the blockchain and digital transactions.

It's goal is to be as simple as possible but complete enough to technically understand what's going on behind Bitcoin or Ethereum for example.

Blockchains are P2P softwares. To start using coincoin, we need to setup multiple nodes and connect them together.

You need Elixir installed. Clone this repository and go to the root of the project.

Then pull the dependencies using mix deps.get

To setup a 3 nodes blockchain, spawn 3 tabs in your terminal (node1, node2 and node3) and run:

• node1: iex -S mix phx.server (defaults: PORT=4000 P2P_PORT=5000)
• node2: PORT=4001 P2P_PORT=5001 iex -S mix phx.server
• node3: PORT=4002 P2P_PORT=5002 iex -S mix phx.server

Then connect the nodes to create a P2P network:

$node2> Blockchain.connect("localhost:5000") # connect node2 to node1

$node3> Blockchain.connect("localhost:5001") # connect node3 to node2

This will setup a simple network:

node1 <--> node2 <--> node3

You can also use the robinmonjo/coincoin docker image available on the docker hub:

docker run -it robinmonjo/coincoin

If you use Docker, in the Blockchain.connect/1 call make sure to pass your container IP address and that this address is reachable.

Notes:

• if you don't want to interact with the REST API, you can skip the PORT env var and use iex -S mix instead of iex -S mix phx.server
• Blockchain.connect(5000) is equivalent to Blockchain.connect("localhost:5000")
• for releases use make release

When started, coincoin will start 3 apps:

• blockchain: a minimal blockchain
• token: a minimal cryptocurrency implemented on top of the blockchain
• blockchain_web: a web interface to manage nodes of the blockchain

To manipulate the blockchain and store random data in it using the iex console checkout the blockchain app. To do the same using a REST API, checkout the blockchain_web app. And finally to play with a cryptocurrency and use the blockchain as a distributed ledger, checkout the token app.

Lately I heard a lot about:

1. how Elixir is awesome and is the future of complex system / web development
2. how blockchain technology will be the next big thing

So what about building a cryptocurrency proof-of-concept in Elixir ?

As I'm sure about 1, I still have some doubts about 2 eventough technologies behind cryptocurrencies are exciting.

Also "coin-coin" in french is the noise of a duck (hence Scrooge McDuck)

Issues, suggestions and pull requests are very welcome 😊