B9Lab Community Blockstars 2019 - Ethereum Developer Course

Remittance Project

You will create a smart contract named Remittance whereby:

there are three people: Alice, Bob & Carol.
Alice wants to send funds to Bob, but she only has ether & Bob does not care about Ethereum and wants to be paid in local currency.
luckily, Carol runs an exchange shop that converts ether to local currency.
Therefore, to get the funds to Bob, Alice will allow the funds to be transferred through Carol's exchange shop. Carol will collect the ether from Alice and give the local currency to Bob.

The steps involved in the operation are as follows:

Alice creates a Remittance contract with Ether in it and a puzzle.
Alice sends a one-time-password to Bob; over SMS, say.
Alice sends another one-time-password to Carol; over email, say.
Bob treks to Carol's shop.
Bob gives Carol his one-time-password.
Carol submits both passwords to Alice's remittance contract.
Only when both passwords are correct does the contract yield the Ether to Carol.
Carol gives the local currency to Bob.
Bob leaves.
Alice is notified that the transaction went through.
Since they each have only half of the puzzle, Bob & Carol need to meet in person so they can supply both passwords to the contract. This is a security measure. It may help to understand this use-case as similar to a 2-factor authentication.

Stretch goals:

did you implement the basic specs airtight, without any exploit, before ploughing through the stretch goals?
add a deadline, after which Alice can claim back the unchallenged Ether
add a limit to how far in the future the deadline can be
add a kill switch to the whole contract
plug a security hole (which one?) by changing one password to the recipient's address
make the contract a utility that can be used by David, Emma and anybody with an address
make you, the owner of the contract, take a cut of the Ethers smaller than what it would cost Alice to deploy the same contract herself
did you degrade safety in the name of adding features?

Clone this repository locally:

git clone https://github.com/theTechRebel/remittance.git

Install dependencies with npm :

npm install

Build the App with webpack-cli:

(for windows)

.\node_modules\.bin\webpack-cli --mode development

(for unix):

./node_modules/.bin/webpack-cli --mode development

Start Ganache and launch a quickstart testnet

Deploy the smart contract onto your Ganache blockchain:

truffle migrate

Fire up an http server for development

npx http-server ./build/app/ -a 0.0.0.0 -p 8000 -c-1

Open the app in your browser with a Meta Mask plugin installed (preferably)