Udacity Blockchain Developer Nanodegree Program - Capstone: Real Estate Marketplace

The capstone will build upon the knowledge gained in the course in order to build a decentralized housing product.

Getting Started

These instructions will get you a copy of the project up and running on your local machine for development and testing purposes.

Prerequisites

Please make sure you've already installed ganache-cli, Truffle and enabled the MetaMask extension in your browser.

Installing

A step by step series of examples that tell you have to get a development environment running.

Clone this repository and install all requisite npm packages (as listed in package.json):

npm install

Change into the contracts folder:

cd eth-contracts

Launch Ganache:

ganache-cli -m "tattoo endless undo gold uniform deny era mean spot width execute impose"

In a separate terminal window, compile the smart contracts:

truffle compile

This will create the smart contract artifacts in folder build/contracts.

Migrate smart contracts to the locally running blockchain, ganache-cli:

truffle migrate

Test the smart contracts:

truffle test

All 11 tests should pass and your terminal should look something like this:

ZoKrates

The code repository already contains 10 pre-generated proofs that have been used to mint 10 tokens. The following instructions explain how the proofs have been generated.

• Step 1: Run Docker

  sudo systemctl start docker
  
  # In case SELinux prevents access to the local drive
  sudo su -c "setenforce 0"
  

• Step 2: Run ZoKrates

  docker run -v `pwd`/zokrates/code/:/home/zokrates/code -ti zokrates/zokrates /bin/bash
  

  Change into the square directory

  cd code/square/
  

• Step 3: Compile the program written in ZoKrates DSL

  ~/zokrates compile -i square.code
  

• Step 4: Generate the trusted setup

  ~/zokrates setup
  

• Step 5: Compute witness

  ~/zokrates compute-witness -a 3 9
  

• Step 6: Generate proof

  ~/zokrates generate-proof
  

• Step 7: Export verifier

  ~/zokrates export-verifier
  

Re-run steps 5 and 6 with different arguments, e.g. 2 4, to generate additional proofs for minting tokens.

Deploy smart contracts on a public test network (Rinkeby)

Create the following files in the eth-contracts folder:

• .infura-key: Your Infura key
• .mnemonic: Your MetaMask seed phrase (mnemonic)

Execute the following command deploy the contracts to Rinkeby:

truffle migrate --network rinkeby --reset

The smart contracts are deployed on the Ethereum Rinkeby test network:

• NipaHutERC721Token: 0x255837801Cd69aEd704Da884aF5BC2e2E14013db
• SquareVerifier: 0xB8a0dc165DECF0e5a28a5EB8F9b7e6605235eBD3
• SolnSquareVerifier: 0xC74013ee20CeD12A2D531594D71585E22168b9e2

Minting tokens

Before tokens can be minted, a new solution for the given token ID needs to be submitted, e.g.:

node submit-solution.js ../zokrates/code/square/proofs/5/proof.json 5

Now the token can be minted, e.g.:

node mint-token.js 5

Generate OpenSea marketplace

Use the OpenSea Rinkeby environment to list the SolnSquareVerifier token (0xC74013ee20CeD12A2D531594D71585E22168b9e2).

After listing, the marketplace should look like this:

Check out the Nipa Hut Token assets on OpenSea: https://rinkeby.opensea.io/category/nipahuttoken

Requirements

Graded according to the Project Rubric.

Project Resources

• Remix - Solidity IDE
• Visual Studio Code
• Truffle Framework
• Ganache - One Click Blockchain
• Open Zeppelin
• Interactive zero knowledge 3-colorability demonstration
• Docker
• ZoKrates

Versions

• Truffle v5.0.18 (core: 5.0.18)
• Solidity - ^0.5.2 (solc-js)
• Node v10.15.3
• Web3.js v1.0.0-beta.37

License

• MIT license
• Copyright 2019 © Thomas Weibel.