Book Image

Blockchain Quick Start Guide

By : Xun (Brian) Wu, Weimin Sun
Book Image

Blockchain Quick Start Guide

By: Xun (Brian) Wu, Weimin Sun

Overview of this book

Blockchain is a technology that powers the development of decentralized applications.This technology allows the construction of a network with no single control that enables participants to make contributions to and receive benefits from the network directly. This book will give you a thorough overview of blockchain and explain how a blockchain works.You will begin by going through various blockchain consensus mechanisms and cryptographic hash functions. You will then learn the fundamentals of programming in Solidity – the defacto language for developing decentralize, applications in Ethereum. After that, you will set up an Ethereum development environment and develop, package, build, and test campaign-decentralized applications.The book also shows you how to set up Hyperledger composer tools, analyze business scenarios, design business models, and write a chain code. Finally, you will get a glimpse of how blockchain is actually used in different real-world domains. By the end of this guide, you will be comfortable working with basic blockchain frameworks, and develop secure, decentralized applications in a hassle-free manner.
Table of Contents (14 chapters)
Title Page
Copyright and Credits
About Packt

Common smart contract patterns

In this section, we will discuss some common design and programming patterns for the smart contract programming language.

Access restriction

Access restriction is a solidity security pattern.  It only allows authorized parties to access certain functions. Due to the public nature of the blockchain, all data on the blockchain is visible to anyone. It is critical to declare your contract function, state with restricted access control, and provide security against unauthorized access to smart contract functionality.

pragma solidity ^0.4.24;
contract Ownable {
 address owner;
 uint public initTime = now;
 constructor() public {
 owner = msg.sender;
 //check if the caller is the owner of the contract
 modifier onlyOwner {
 require(msg.sender == owner,"Only Owner Allowed." );
 //change the owner of the contract
 //@param _newOwner the address of the new owner of the contract.
 function changeOwner(address _newOwner) public onlyOwner {
 owner = _newOwner;