Final Project for Blockchain NanoDegree that requires to mint own tokens to represent the title to the properties. Before minting the token, the owner needs to verify she/she owns the property. A zk-SNARKs (zoKrates) mechanism will be used to create a verification system which can prove the ownership of title to the property without revealing that specific information on the property. Once the token has been verified it will be placed on a blockchain market place (OpenSea) for others to purchase.

Although is is optional, a UI has been provided in order to help viewing and minting tokens (with or without approved solution) The optional front-end of the application runs on the client's machine, powered by a lite-server. Using web3/metamask , it communicates with the deployed smart contract from Rinkeby.

   > transaction hash:    0xebbbfe20ac43b0d13f1ff771a4b1b504a4267ae6e23c7f82b104a2c432a07366
   > Blocks: 0            Seconds: 9
   > contract address:    0x976148e0616bb79496EFc35B2721074304851FbF
   > block number:        4416748
   > block timestamp:     1558380765
   > account:             0x4FdA5baf52B8ff93399673F3f89A93ef31066AD8

   > transaction hash:    0x32be17f14f0119265795a113fd551839855f2682c36a865313b320a6817f9cd1
   > Blocks: 0            Seconds: 5
   > contract address:    0xcA11214d11F50FC700Ee18a68102bD5EdC9A84B6
   > block number:        4416749
   > block timestamp:     1558380780
   > account:             0x4FdA5baf52B8ff93399673F3f89A93ef31066AD8

Can be found on eth-contracts/build/contracts folder on github cloned repository

• Original minter : https://rinkeby.opensea.io/accounts/0x4fda5baf52b8ff93399673f3f89a93ef31066ad8
• Buyer : https://rinkeby.opensea.io/accounts/0x15e542f44d1f0811ec4453fa5493eff1859f89b6

• Deployed SolnSquareVerifier Contract Owner The address of the owner who deployed the contract. Can be acquired via using Get Contract Owner button
• View token details allows to input a token id and upon using Get Token details button, Token Owner & Token URI fields will be populated
• Token Owner & Token URI displays the basic info about the token id
• Token balance for address Allows to input an address and upon selecting Get token balance will populate the field Balance
• Balance - gets populated with the number of tokens owner by Token balance for address after pressing Get Token Balance

• Get Contract Owner Reads and populates Deployed SolnSquareVerifier Contract Owner field with the address of the contract owner
• Get Token Details - Returns the basic token details for the token id of View token details field
• Get Token Balance Populates the Balance field with the number of tokens owned by Token balance for address

• Proof A [0], Proof A [1], ..input The values generated by Zokrates in the proof.json. Defaulted to the values generated when running 3 9 as solution. This token is already registered!

• Approve Solution Attempts to approve the inserted solution. MetaMask will reject the transaction if proof cannot be verified.

• Input [0] & Input [1] Attempts to mint a token with a previous validated/approved solution. The two inputs are the inputs from proof.json
• Address To The address to who the token should be given to

• Mint with solution Attempts to mint a token using the Inputs[] and address. If the solution is already used OR unverified, an exception will be thrown. No Token Id is needed as it will use the previously approved solution's autogenerated index as tokenId.

• To To who should the token be given to
• Token ID The Token ID. Will throw exception if token exists already

• Mint Attempts to mint the token. This procedure does not need an approved solution.

Listens and displays several important events emitted by the contract.

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

• NodeJS (The install will also include the npm node package manager)
• ganache-cli Fast Ethereum RPC client for testing and development
• truffle Development environment, testing framework and asset pipeline for Ethereum
• MetaMask extension installed in your browser and few ethers on Rinkeby Test Network.
• Docker Enterprise Container Platform for High-Velocity Innovation

node -v
npm -v
npm i ganache-cli -g
npm i truffle -g

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

Clone this repository:

git clone https://github.com/StefanelStan/Blockchain-Capstone-Real-Estate-Marketplace.git

Change directory to P8 folder and install all requisite npm packages (as listed in package.json):

cd P8
npm install

1. Start a local ganache-cli instance

ganache-cli

2. In a separate terminal window, Compile the contracts: This will create the smart contract artifacts in folder build\contracts.

cd eth-contracts
truffle compile

3. Run the test command

cd eth-contracts
truffle.cmd test

All 36 tests should pass.

1. Launch Ganache-cli: It is important to use a mnemonic for the ganache-cli and the given arguments. The same mnemonic will be used in Metamask to import the accounts

ganache-cli -m "word1 word2 word3 ....word12"

2. Compile & Deploy the contracts: In a separate terminal window deploy the contracts on ganache development network. Make sure you fill in your infuraKey and mnemonic into eth-contracts/config/

cd eth-contracts
truffle.cmd migrate --network development

3. In the same (or a new terminal) launch the dapp

cd P8
npm run dev

1. Navigate to project folder cd P8\zokrates\code\

2. Run the zokrates docker image docker run -v $(pwd):/home/zokrates/code -ti zokrates/zokrates:0.3.0 /bin/bash

3. Compile the program

cd code
~/zokrates compile -i square/square.code

4. Generate the trusted setup ~/zokrates setup

5. Compute witness for your desired pair of number - square (the project already contains proof for [3,9] , [4-16] squares) ~/zokrates compute-witness -a number square

6. Generate proof ~/zokrates generate-proof At this point there should be a proof.json file that contains the ProofA[], ProofB[] fields that can be used to Approve Solution as described in the document UI

7. (Optional) Generate verifier.sol ~/zokrates export-verifier

Truffle v5.0.15 (core: 5.0.15)
Solidity - 0.5.2 (solc-js)
Node v10.15.3
Web3.js v1.0.0-beta.37

• Chai- BDD / TDD assertion library for node. It provides easy to read asserts and expects as well at matchers (greater, between, before, contains etc)
• truffle-assertions - Additional assertions and utilities for testing Ethereum smart contracts in Truffle unit tests. Used to listen for events

• Ethereum - Ethereum is a decentralized platform that runs smart contracts. The SupplyChain contract is deployed on Rinkeby Test Network
• Truffle Framework - Truffle is the most popular development framework for Ethereum with a mission to make your life a whole lot easier. Used for development and testing.
• ganache-cli Ganache CLI, part of the Truffle suite of Ethereum development tools, is the command line version of Ganache. Used to kickstart a a evm and personal blockchain to deploy and test the contract locally.
• web3js Ethereum JavaScript API.
• truffle-hdwallet-provider - HD Wallet-enabled Web3 provider. Use it to sign transactions for addresses. Used in truffle.cmd for deployment of contracts
• Visual Studio Code - Web editor
• lite-server - Lightweight development node server for serving a web app. Used to kickstart the http server to deploy the html and js to interract with the dapp.
• Open Zeppelin
• Interactive zero knowledge 3-colorability demonstration
• Docker
• ZoKrates

• Stefanel Stan - Stefanel Stan Github

• Author wishes to thank Stackoverflow for providing great free services and to the three online resources listed below for sharing their helpful knowledge
• Udacity Blockchain ND very helpful mentors Alvaro and DanielA

This project is licensed under the MIT License