The program simulates a stock market with user accounts, portfolios, and trading capabilities. It also includes features such as encrypted data storage to protect user information and market data. Here's a breakdown of the main components and their functions:

Key Management: The program generates and manages a secret key for encryption. This key is used to encrypt and decrypt data files to ensure that sensitive information remains secure. Data Storage: User information, portfolios, and market data are saved to and loaded from encrypted files. The files include: users_data.pkl for storing user credentials and portfolio references. {username}_portfolio.pkl for storing individual user portfolios. market_data.pkl for storing market stock information.

Stock Represents a stock in the market. Each stock has:

Symbol: A unique identifier for the stock (e.g., "AAPL"). Price: The current trading price of the stock. Quantity: The number of shares available in the market. History: A record of price changes over time. Portfolio Represents a user's collection of stocks and their financial balance. It includes:

Stocks: A dictionary of stocks owned by the user, with quantities. Balance: The amount of money available for trading. Transaction Fee: A fixed fee applied to each transaction (buy or sell). Methods include:

buy_stock: Allows the user to buy a specified quantity of a stock if sufficient balance and quantity are available. sell_stock: Allows the user to sell a specified quantity of a stock if sufficient shares are owned. get_portfolio_value: Calculates the total value of the portfolio, including the balance and the current value of owned stocks. Market Represents the stock market. It contains:

Stocks: A dictionary of available stocks in the market. Methods include:

add_stock: Adds a new stock to the market with an initial price and quantity. get_stock: Retrieves information about a specific stock. update_market: Updates stock prices based on simulated market fluctuations. User Represents an individual user, including their credentials and portfolio.

UserManager Manages user registration and login. It provides:

register: Registers a new user. login: Authenticates a user and retrieves their portfolio.

Main Menu: Users can view the market, register, log in, or exit the program. User Menu: After logging in, users can: View their portfolio. Buy or sell stocks. Add new stocks to the market. Update market prices. Check the transaction fee.

Serialization: Converts Stock, Portfolio, and Market objects into a format suitable for saving to a file (using pickle). Deserialization: Converts saved data back into objects when loading from a file.

The program includes basic error handling for scenarios such as insufficient balance, insufficient stock quantity, and invalid user actions.