Create your first permissioned blockchain

Multichain a is open source, bitcoin forked, permissioned blockchain solution.

• Rather than public blockchain, like Ethereum or bitcoin, the transactions and activities are kept private to the selected participants.

• Admin/Admins can make sure, which participants can connect to the blockchain and even read or write on the platform.

• With all these goodies, although PoW is optional here, we can also include wallets, assets and create our own currency.

Objectives

In this article, using multichain, we will create a permissioned blockchain solution.

• Create two nodes
• Each node will have a copy of chain
• We tweak some permission between these nodes
• Create a block data in the first node chain and Make sure, that block data is available in the sibling node chain

Prerequisites:

• Two ubuntu instances (AWS EC2 is used here)

Before we start, please create 2 ubuntu instances under same network. Let's call the first one origin_node and the second one sibling_1 node.

• origin_node
  • Genesis node will be created here, Admin node

• sibling_1
  • Has permission to connect and write to the chain

For creating instance, please consider the following criteria

• Use ubuntu 16.04 server

• Use a security group that allows
  • HTTPS 443
  • SSH 22
  • Custom TCP 8333

Prepare origin_node:

Objective of this section is create a genesis node and run the chain. SSH to your origin_node.

ssh ubuntu@origin_node_public_ip -i key

Become a root user

sudo su

Download multichain

wget https://www.multichain.com/download/multichain-2.0-alpha-5.tar.gz

Extract files:

tar -xvzf multichain-2.0-alpha-5.tar.gz

Move files to binary directory

cd multichain-2.0-alpha-5
mv multichaind multichain-cli multichain-util /usr/local/bin

Return to home directory

cd ~

Create a genesis node

multichain-util create my-blockchain

Update default network and rpc port to 8333 and 8332

nano /root/.multichain/my-blockchain/params.dat

You can use the default network port. But you have to ensure to put the port explicitly in next command.

Now run the node

multichaind my-blockchain -daemon

You will get response like,

Other nodes can connect to this node using:
multichaind my-blockchain@origin_node_ip:8333

Now configure HTTPS and default network port firewall.

HTTPS for syncing and interacting other nodes and default network port to connect with other nodes.

ufw allow OpenSSH
ufw allow in 443/tcp
ufw allow in 8333/tcp
ufw enable
ufw status

We successfully run a multichain node.

Prepare a sibling node:

Just like the previous origin_node install multichain.

ssh ubuntu@origin_node_public_ip -i key
sudo su
wget https://www.multichain.com/download/multichain-2.0-alpha-5.tar.gz
tar -xvzf multichain-2.0-alpha-5.tar.gz
cd multichain-2.0-alpha-5
mv multichaind multichain-cli multichain-util /usr/local/bin
cd ~

Initialize chain from origin_node

multichaind my-blockchain@private_ip_of_origin_node:8333

Now you should get a wallet address for further transaction.

Great, one sibling node is initialized.

Right now it's chain is initialized. But it does not have any permission for connect or write to the chain.

Grant Permission from origin_node:

We will grant Permission of sibling_node for connect and write to the chain.

From the origin_node, grant permission to connect and write,

multichain-cli my-blockchain grant sibling_1_node_wallet_address connect,send,receive,mine,create

Since permission is granted, now we can connect and write data to the chain from sibling_1 node.

Write Some Data From Sibling Node

Go to your sibling_1 and connect to the chain,

multichaind my-blockchain -daemon

To write some json data, go to interactive mode,

multichain-cli my-blockchain

Create a stream to mine some block,

create stream my-blockchain-stream true

Write data through the stream

publish my-blockchain-stream "json" '{"json":{"myKey":"myValue"}}'

Make sure, there is no space between the colon, cottation or brackets

It's time to check, chain is synced among all the nodes.

Verify Chain Data in origin_node

Now the chain data should synced through all the nodes. To check this, Go to the origin_node and check if the data block exists in the chain. In the origin_node, Go to interactive mode,

multichain-cli my-blockchain

Subscribe to the stream

subscribe my-blockchain-stream true

Now your data should be displayed

liststreamitems my-blockchain-stream

You will get output something like this,

[
  {
    "publishers": ["1aokp3bti15AuRs51wPemtBuiqAdRDFaGYnRQw"],
    "keys": ["json"],
    "offchain": false,
    "available": true,
    "data": {
      "json": {
        "myKey": "myValue"
      }
    },
    "confirmations": 4,
    "blocktime": 1571709550,
    "txid": "transaction_id"
  }
]

Wrap Up:

References:

• Video Course: https://www.udemy.com/course/build-blockchain-deploy-private-blockchain/
• Official Getting Started: https://www.multichain.com/getting-started/

• Permissions: https://www.multichain.com/developers/permissions-management/
• Runtime Parameters: https://www.multichain.com/developers/runtime-parameters/

Exercise:

• Create 2nd sibling with read permission and read chain
• Create 3rd sibling with write permission and verify chain
• Integrate a express server