Introduction to Web 3

Blockchains, DApps and smart contracts

What is blockchain?
- Block structure
- Block time
- Transaction
- Ethereum
What are DApps?
- Why DApps
- Decentralized Vs Federated
What is a smart contract?
- Structure
- Environment
- Solidity
Create your first Smart contract!

Blockchain

Block

A block is a Node in a blockchain where information is stored and encrypted.

Block #
Nonce
Data
Hash

Mining is the process where we try to fit the 'nonce' to get a signed block.

Block #
Nonce
Prev
Data
Hash

A blockchain is a series of blocks, where prev refers to the block# of previous node.

Replace Data with transactions

Block #
Nonce
Prev
Tx : $10->Bill
$20->Clive
Hash

Add Coinbase to keep track of transaction amount in the account

Block #
Nonce
Prev
Cb: $70
Tx : $10->Bill
$20->Clive
Hash

Block time

The amount of time that it takes to check the hash and find a nonce which is less than the target value

The average block time gets compared with the expected block time, and if the average block time is higher, then the difficulty is decreased in the block header. If the average block time is smaller, then the difficulty in the block header will be increased.

Transaction

Message
- amount
- from
- to
private key
message signature

signed message = message + private key

verify = message + public key + signed message

A record that describes one account sending money to another.

Nonce
to
value
gas price
start gas
v
r
s

private key => v+r+s

v+r+s => sender's address

We create a transaction object and submit to a network

Ethereum

The ultimate smart contract and decentralized application platform

Its white paper introduces the idea of 'smart contracts' as an entity that can send and receive money beyond just humans

When we interact with a node in Ethereum network for a transaction, our transaction along with other transactions happening in the network are put together as a "block" in the block chain

Decentralized Apps

Digital applications or programs that exist and run on a blockchain or peer-to-peer (P2P) network of computers instead of a single computer.

They are outside the control of a single authority. DApps—which are often built on the Ethereum platform—can be developed for a variety of purposes including gaming, finance, and social media.

Smart Contracts

Structure

Rinkeby

Contract Instance

deployment

Contract Source

Solidity

Contract definition

|

solidity compiler

|

Byte code for deployment | Application Binary Interface(ABI)

JS -> ABI -> Byte code preview

Invented specifically for authoring smart contracts
.sol files
strongly typed

Solidity - v4

pragma solidity ^0.4.12

contract Inbox{
  string public message;

  function Inbox(string initialMessage) public{
    message = initial message;
  }

  function setMessage(string newMessage) public{
    message = newMessage;
  }

  function getMessage() public view returns(string){
    return message;
  } 
}

Solidity - v8

// SPDX-License-Identifier: GPL-3.0

pragma solidity >=0.7.0 <0.9.0;
pragma abicoder v2;

contract Message {
    string message;

    constructor(string memory initialMessage) {
        message = initialMessage;
    }

    function setMessage (string memory newMessage) public{
        message = newMessage;
    }
    
    function getMessage() public view returns(string memory){
    	return message;
    }

}