• 1. Introduction
• 2. Getting Started
  • 2.1. Requirements
  • 2.2. Directory structure
  • 2.3. Configuration
  • 2.4. Start the Application
• 3. End-to-end communication
  • 3.1. User Registration
  • 3.2. User Login
  • 3.3. Friend request
  • 3.4. Chat
• 4. Future Improvements

Introduction

This project consists of a real-time chat application where registered users can send messages to their friends using end-to-end communication.

Getting Started

Requirements

You should have installed:

• Node
• Yarn (or NPM)
• MongoDB

Directory structure

• api contains all of the API server's files directory;
  • api/socketio-server is the Socket.io server directory for real-time communication;
  • api/src contains all of the Server core files;
  • api/.env.example contains all of the NestJS Server's configuration supported variables.
• client Vue client application folder;
  • client/src contains all of the Vue client's core files;
  • client/.env.example stores all of the client's configuration supported variables.

Configuration

If you have already installed Mongo and you're running an instance of it, you can configure the API server enviroment variables in order to start it correctly. Move inside api directory, copy the .env.example file, rename it .env and edit it with your custom values.

# JWT secret used from the server to sign generated tokens
JWT_SECRET=create a complex string without spaces
# Expiry time of the generated tokens
JWT_EXPIRY_IN_SECONDS=180
# Rounds to compute for every single generated BCrypt hash.
BCRYPT_SALT_ROUNDS=10
# Your Mongo connection string
MONGO_DB_URL=mongodb://localhost/<db_name>

Start the application

Open 3 terminals:

# start the API server
# make sure you have Mongo running first
cd api

# or npm install
yarn

# or npm run start
yarn start



# start the socket.io server for real-time communication
cd api/socketio-server

# or npm install
yarn

# or npm run start
yarn start



# start vue client
cd client

# or npm install
yarn

# or npm run dev
yarn dev

End-to-end communication

User Registration

During registration, the user needs to create a strong password that will be used to encrypt a just generated RSA Private key which, with the Public one can chat togheter. one will be stored with the user's information.

User Login

When a user logs in, the client fetches from the server all the user's data including the encrypted Private key and uses the just insert password to decrypt the key and save it into the localStorage of the browser. It will be fundamental to decrypt all chat messages.

Friend request

In order to message with a registered user, you need to send a friend request first. If the invited user accepts your request, you will both receive each other's Public key and can chat togheter.

⚠️ The Public key will never be encrypted and can also be published because it only encrypts all the messages to send.

Chat

You can chat with your friends because you know their Public key. When you want to send a message, the client prepares two messages to send to the server:

• a message encrypted with your Public key;
• a message encrypted with your friend/receiver Public key.

Therefore for each message sent, one copy can be read only by you and the other only by your friend.

Future Improvements

• Create a secret key shared between sender and receiver for each conversation to save 50% of the space when storing messages and eliminate the need to save two copies for each message.