The purpose of this project is to demonstrate the ability to record identity-related transactions on a private blockchain. The idea is to record actions or events associated with resources with which an identity may interact, typically called entitlements.

I started with the Ethereum Project since it supports so called “smart contracts” and was designed for uses other than pure digital cash transactions as is the case with Bitcoin. I chose the Golang implementation, go-ethereum.

Running in Docker

In order to get up and running quickly, I used a Docker container with go-ethereum already installed. The first step is to retrieve the image from DockerHub.

docker pull ethereum/client-go

Start a node with the JSON-RPC interface listening on port 8545.

docker run -it -p 8545:8545 -p 30303:30303 ethereum/client-go --rpc --rpcaddr "0.0.0.0"

https://github.com/ethereum/go-ethereum/wiki/Running-in-Docker

Docker Compose

Create a docker-compose file with the settings above.

# docker-compose up -d

geth:
    container_name: client-go
    image: ethereum/client-go
    ports:
        - "8545:8545"
        - "30303:30303"
    command: --rpc --rpcaddr "0.0.0.0" --rpcapi "db,eth,net,web3" --rpccorsdomain "*" --testnet --nodiscover

Bring the container up: docker-compose up -d.

~\src\ethereum [master ≡ +1 ~0 -0 !]> docker ps
CONTAINER ID        IMAGE                COMMAND             CREATED              STATUS              PORTS                                              NAMES
21189ed24134        ethereum/client-go   "/geth"             About a minute ago   Up About a minute   0.0.0.0:8545->8545/tcp, 0.0.0.0:30303->30303/tcp   client-go
~\src\ethereum [master ≡ +1 ~0 -0 !]> docker exec -it 21189ed24134 /bin/bash
root@21189ed24134:/# ls
bin  boot  dev  etc  geth  home  lib  lib64  media  mnt  opt  proc  root  run  sbin  srv  sys  tmp  usr  var

Confirm the server is running with the intended switches.

root@20c354e83cf1:/# ps aux
USER        PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root          1  0.3  3.0 326624 61820 ?        Ssl  19:09   0:01 /geth --rpc --rpcaddr 0.0.0.0 --rpcapi db,eth,net,web3
root         13  0.0  0.1  18240  3388 ?        Ss   19:11   0:00 /bin/bash
root         41  0.0  0.1  34424  2760 ?        R+   19:14   0:00 ps aux

Attach to the console.

root@21189ed24134:/# ./geth attach
Welcome to the Geth JavaScript console!

instance: Geth/v1.5.8-stable-f58fb322/linux/go1.6.2
 modules: admin:1.0 debug:1.0 eth:1.0 miner:1.0 net:1.0 personal:1.0 rpc:1.0 txpool:1.0 web3:1.0

>

Ethereum Quick Start

Below is a quick bash script to start go-ethereum. The default ports are fine.

RPC Port: default: 8545
Port default: 30303

# geth.sh
# Fetch local IP address into a variable.
MY_IP=$(ip addr list enp0s25 | grep "inet " | cut -d' ' -f6 | cut -d/ -f1)

# --testnet and --dev are mutually exclusive
~/src/ethereum/go-ethereum/build/bin/geth \
  --testnet --identity "IGBlock" \
  --rpc --rpcaddr "$MY_IP" --rpccorsdomain "*" \
  --nodiscover --rpcapi "db,eth,net,web3" console

This creates a blockchain on the Ethereum TEST-NET. It is possible to create a private blockchain as well using the --networkid 1999 switch. See Setting up a local private testnet for more detail.

REST Client

Since go-ethereum supports a JSON-RPC interface, I use the Chrome DHC extension (similar to Postman) as a RESTful client.

Mist

Ethereum also supports a rich, native client based on Meteor called Mist. You may recognize Meteor as the Rocket.Chat native application is based on it as well.

To get Mist to connect to your private blockchain, use the --rpc command line switch, e.g.

Mist.exe --rpc http://10.45.14.31:8545

Windows users may set up a shortcut for the Mist application.

Here you can see the blockchain and the Ether that has been “mined” so far.