MSc Project

• Marinos Iliadis
• University of Southampton 2017-2018
• MSc Data Science

Project Title

Maintaining Privacy in Database and Data exchange using Blockchain Mechanisms and Smart Contract

How to import the project into Eclipse

• Open Eclipse -> Go to File -> Open Project From File System -> Show other specialised import wizard-> Gradle -> Existing Gradle -> sample-project-gradle-master
• Import this project to Eclipse (I use Eclipse Oxygen 3A) as an existing Gradle project.
• Our eclipse project uses the web3j library. Java library to interact with Ethereum blockchain and solidity smart contracts
• Run the "Application.java"

Functionality

This decentralised application shows an Access control mechanism in order to increase the privacy in data exchange using smart contract and blockchain technology

• Communicate and Interact from Java dapp
• Connecting to nodes on the Ethereum network
• Load our Ethereum wallet file
• Send Wei(ether) from our address to another address (based functionality).
• Deploy our smart contract to the blockchain netwrok
• Creating Access Control List for authorised user (add, delete users) using their Ethereum adresses
• Validate user using the ACL (isUser)
• Insert, get, update, delete, count users in the data storage of our smart contract
• Updating a value in our smart contract
• Viewing events logged in the smart contract

Ethereum wallet

• To use our java dapp need to have an Ethereum wallet. Set up a password.
• This can be generated using the web3j command line tool.
• https://docs.web3j.io/command_line.html

OR

• Using the MyEtherWallet website to create an Ethereum wallet file
• https://www.myetherwallet.com/

Manage account

• By using MetaMask Google Chrome Extension
• Check how it works here:
• https://metamask.io/

OR

• By visiting Etherscan's website and add the address to the search bar
• https://etherscan.io/

Request some Ether from Faucet

• Import the wallet file into the MetaMask account.
• Change from Main Netwotk to Ropsten Network and click the Buy button.
• Then, click Ropsten test Faucet.
• Request Ether several times.
• Ether are required for the deployment and the interaction with the functions of our smart contract

Smart contracts

• There are several smart contracts in this dapp, the most updated one is the "Acladv.java".
• You can find all smart contracts of my project in the folder src/main/resources insolidity type (.sol)
• You can test them in https://remix.ethereum.org/ as well

Infura

• Cloud-based ethereum clients. Need to sign in and create a auto generated token in order to use our java dapp.
• https://infura.io/register.html

Testnet

In this prototype java dapp we deploy our contract on the Ropsten Test Network

Solidity compiler and Java wrappers

A. Compiling Solidity source code - 1. npm install -g solc - 2. solc or solcjs .sol --bin --abi --optimize -o /

• Links:
  • https://web3j.readthedocs.io/en/latest/smart_contracts.html
  • https://www.npmjs.com/package/solc
  • http://solidity.readthedocs.io/en/develop/installing-solidity.html

B. Auto generated Java wrapper for solidity smart contract - Need first to save your solidity code into a Notepad++ file with extention .sol

C. Solidity smart contract wrappers - 3. web3j solidity generate [--javaTypes|--solidityTypes] /path/to/.bin /path/to/.abi -o /path/to/src/main/java -p com.your.organisation.name

• Link:
  • https://docs.web3j.io/smart_contracts.html#smart-contract-wrappers

Viewing logs on blockchain

• Logback configuration is provided in the project dependencies giving the opportunity to logging of protocol messages.
• To enable this need to change the following line in the logback config:

<logger name="org.web3j.protocol" level="DEBUG"/>

Extra Dependencies for the project (check build.grandle)

• Assert java 3.10.0
• Javatuples 1.2
• JUnit 4.12 for testing