Cryptora - Offline Text Encryption System

Cryptora is a secure offline text encryption system that allows users to:

• Register and manage user accounts with RSA key pairs.
• Encrypt and send messages securely to other users.
• Import public keys to communicate with external users.
• Decrypt messages received from other users.

This system ensures that users' private keys and public keys are persistently stored for future use, eliminating the need for key regeneration.

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Features

1. User Registration

   • Create a new user account with an RSA key pair.
   • Automatically logs in after successful registration.

2. Login

   • Log in as an existing user to access their private key and messages.

3. Add/Import Public Key

   • Add a new user's public key to communicate securely.

4. List Users and Public Keys

   • View all registered users and their public keys.

5. Send Encrypted Message

   • Encrypt and send a message to a recipient using their public key.

6. Decrypt Message

   • Decrypt messages using the logged-in user's private key.

7. Persistent Storage

   • User data (keys and public keys) is stored in a file (userKeys.dat) for reuse across sessions.

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How to Run

Prerequisites

• Java 8 or higher installed.
• A code editor or terminal to compile and run the program.

Steps

1. Clone or Download the Repository

   git clone https://github.com/your-repo/Cryptora.git
   cd Cryptora

2. Compile the Program

   javac Cryptora.java

3. Run the Program

   java Cryptora

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File Structure

1. Cryptora.java: The main application file.
2. userKeys.dat: Stores user data (keys and public keys).

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Usage

1. Register a User Select option 1 to register a new user. Provide a unique username to generate an RSA key pair.

2. Login Select option 2 to log in to an existing account.

3. Add Public Key Select option 3 to import a public key. You'll need the username and Base64-encoded public key.

4. List Users Select option 4 to view all registered users and their public keys.

5. Send Message Select option 5 to encrypt and send a message. Choose a recipient by username.

6. Decrypt Message Select option 6 to decrypt a received encrypted message.

7. Exit Select option 7 to save all data and exit the application.

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Example Workflow

User A registers and generates an RSA key pair. User B registers and generates their own RSA key pair. User A adds User B's public key using the "Add Public Key" option. User A sends an encrypted message to User B. User B decrypts the message using their private key.

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Persistent Storage

User accounts and their respective keys are saved in the userKeys.dat file. This file ensures that users' data persists across program restarts.

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Notes

Always ensure the userKeys.dat file is kept secure, as it contains sensitive key data. The encryption is performed using the RSA algorithm with a key size of 2048 bits

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Contributing

Feel free to fork the repository and submit pull requests for new features or bug fixes.

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License

This project is licensed under the MIT License.