User Authentication System

This is a basic C program that implements a simple registration and login system. It allows users to register with a unique username, password, email, and phone number. The system also includes basic login functionality with username and password validation.

Features

• User Registration:

  • Ensures each user has a unique username.
  • Passwords, email, and phone number are stored securely.
  • A simple verification system using a placeholder function (send_verification_code).

• User Login:

  • Checks user credentials against registered users.
  • Allows for up to 3 login attempts before locking out the user.

Code Structure

The project is made up of a single source file:

• source.c: Contains the main program logic, user registration, and login functionality.

Main Functions

• register_user(): Handles user registration. It ensures a unique username and stores the user details in memory. Also includes a placeholder for verification code handling.
• login(): Allows users to log in by validating their credentials (username and password) against previously registered users.
• valid_username(): Checks if the entered username already exists.
• valid_credentials(): Verifies if the provided username and password match any registered user.
• send_verification_code(): Placeholder function to simulate sending a verification code to the user's email and phone.
• valid_verification_code(): Placeholder function to validate a user's verification code.

How to Use

1. Clone the repository:

   git clone https://github.com/yourusername/your-repo-name.git

   cd your-repo-name

2. Compile the code:

   gcc source.c -o login_system

3. Run the program:

   ./login_system

4. The program provides a simple menu where you can:

   Register a new user.

   Log in using an existing username and password.

   Exit the application.

Example Usage

1. Register
2. Login
3. Exit

Enter your choice: 1

Enter a new username: john_doe

Enter a new password: securePass123

Enter your email: john@example.com

Enter your phone number: 123-456-7890

Verification code sent to email: john@example.com and phone: 123-456-7890

Enter the verification code sent to your email and phone: 1234

Registration successful!

1. Register
2. Login
3. Exit Enter your choice: 2

Enter username: john_doe

Enter password: securePass123

Access granted!

Future Enhancements

Password Strength Validation: Implement checks to ensure passwords meet security criteria (minimum length, inclusion of special characters, etc.).

Email and Phone Verification: Add actual functionality for sending and validating verification codes.

Persistent Storage: Store user data in a file or database for persistence.

Contributing

Contributions are welcome! If you find any issues or have suggestions for improvements, feel free to submit a pull request or open an issue.

Happy coding! 😊

This README.md provides a clear overview of the project, instructions on how to use it, and suggestions for future improvements. You can adjust the repository URL, project name, and other details as needed.