Project - ECDSA Node

NOTE: the base code for this project is cloned from the following repo: https://github.com/alchemyplatform/ecdsa-node

Challenge Summary:

The best way to deeply understand blockchain is to put yourself into development mode. What would it be like to build your own blockchain? Let's start by applying our knowledge of hashes and digital signatures to our very first project: ECDSA Node.

In this project you'll have a simple react front-end which will communicate with a single server. This server will be responsible for transferring balances between accounts. Since it's a single server, it is centralized, so we'll need to trust that the server operator is not malicious for this exercise (more on this later!).

🏁 Your Goal: ECDSA

This project begins with a client that is allowed to transfer any funds from any account to another account. That's not very secure. By applying digital signatures we can require that only the user with the appropriate private key can create a signature that will allow them to move funds from one account to the other. Then, the server can verify the signature to move funds from one account to another.

Incorporate Public Key Cryptography so transfers can only be completed with a valid signature
The person sending the transaction should have to verify that they own the private key corresponding to the address that is sending funds

🤔 While you're working through this project consider the security implications of your implementation decisions. What if someone intercepted a valid signature, would they be able to replay that transfer by sending it back to the server?

ECDSA Node

This project is an example of using a client and server to facilitate transfers between different addresses. Since there is just a single server on the back-end handling transfers, this is clearly very centralized. We won't worry about distributed consensus for this project.

However, something that we would like to incorporate is Public Key Cryptography. By using Elliptic Curve Digital Signatures (ECDSA) we can make it so the server only allows transfers that have been signed for by the person who owns the associated address.

Video instructions

For an overview of this project as well as getting started instructions, check out the following video:

https://www.loom.com/share/0d3c74890b8e44a5918c4cacb3f646c4

Project:

UI & API Details

Server:
- There are 3 pre-defined wallet addresses and balances for you to use in ./server/index.js that get specified from ./server/.env:
  - Address: ${process.env.KEY_CARD_ONE_ADDRESS} - Balance: 100
  - Address: ${process.env.KEY_CARD_TWO_ADDRESS} - Balance: 50
  - Address: ${process.env.KEY_CARD_THREE_ADDRESS} - Balance: 75
Client:
- The left-hand side of the UI (titled "Your Wallet") shows you the wallet and account balance.
  - Type in one of the wallet address privateKey's from ./server/.env
- The right-hand side of the UI (titled "Send Transaction") is where you can send an amount to a specified wallet address.

Tips

Helpful Resources

We're going to be incorporating the concepts we learned from this week into the final project. Here are a few resources you'll find helpful when working on this project:

Public Key Exercises in the Digital Signatures lesson (Recover Keys, Sign Message, Hash Messages)
The Ethereum Cryptography library (specifically random private key generation)

Optimal Solutions

As with all open-ended projects, there are multiple solutions we can build here, a few are better than others. We recommend watching the video walk-through to understand what the optimal solutions are and tradeoffs that come with each path.

Setup:

Clone the repository to your machine, then setup both the Client and Server using the following steps:

Client

The client/ folder contains a react app using vite.

To get started, follow these steps:

Open up a terminal in the ./client folder
Run npm install to install all the dependencies
Run npm run dev to start the application
Now you should be able to visit the app at http://localhost:5173/

Server

The server/ folder contains a node.js server using express.

To run the server, follow these steps:

Open a terminal within the ./server folder
Install dependencies
```
npm i
```
Duplicate .env-sample to .env and setup the ENV variables:
```
cp .env-sample .env
node scripts/generateTestAddresses.js
```
- Copy the outputs from the generateTestAddresses.js script to the correct .env variables
Run the project locally:
```
npm run dev
```
The application should connect to the default server port 3042 automatically!

(http://127.0.0.1:3042/)

skplunkerin / ecdsa-node--alchemy_university-week1-projects