File Encryption and Decryption Tool

Introduction

This Python tool provides a flexible way to encrypt and decrypt files. It supports two methods of key management:

1. Stored Key Method: Uses a securely generated key saved to a file (secret.key).
2. Password-Based Key Derivation: Derives the encryption key from a user-provided password using PBKDF2 HMAC-SHA256 with a unique, random salt.

By combining both methods into a single script, users can choose the approach that best fits their needs, balancing convenience and security.

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Features

• Flexible Key Management: Choose between a stored key or password-derived key.
• Strong Encryption: Utilizes the Fernet symmetric encryption, which is built on AES 128 in CBC mode and uses HMAC for authentication.
• Password Strength Enforcement: Ensures that passwords meet complexity requirements for enhanced security.
• Unique Salt Generation: For password-based encryption, a new random salt is generated for each file.
• Password Confirmation: Prevents accidental typos by requiring password confirmation during encryption.
• Cross-Platform: Works on any system with Python 3.x installed.
• Error Handling: Provides informative messages for common errors and issues.

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Requirements

• Python 3.x
• cryptography Library

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Installation

1. Clone the repository

   git clone https://github.com/Vikranth3140/Encryption-Decryption-Tool.git

2. Install Required Libraries

   Install the cryptography library using pip:

   pip install cryptography

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Usage Instructions

The script is executed via the command line and supports the following operations:

• Generate a key (for the stored key method)
• Encrypt a file
• Decrypt a file

Command-Line Options

• -g: Generate a Fernet key and save it to secret.key.
• -e: Encrypt a file.
• -d: Decrypt a file.
• -k: Use the stored key method.
• -p: Use the password-based key derivation method.

1. Generate a Fernet Key (Stored Key Method)

Before encrypting files using the stored key method, you need to generate a key.

python script.py -g

Output:

Encryption key generated and saved to 'secret.key'.

• Note: Keep the secret.key file secure. If it's lost or compromised, encrypted data cannot be decrypted or may be at risk.

2. Encrypt a File

Using Stored Key Method

python script.py -e -k <filename>

• <filename>: The path to the file you want to encrypt.
• The script uses the key stored in secret.key.

Using Password-Based Key Derivation

python script.py -e -p <filename>

• The script will prompt you to enter and confirm a password.

Password Strength Requirements

• At least 8 characters long.
• Contains at least one uppercase letter (A-Z).
• Contains at least one lowercase letter (a-z).
• Contains at least one digit (0-9).
• Contains at least one special character (e.g., !@#$%^&*()).
• If the password doesn't meet these requirements, the script will prompt you to enter a stronger password.
• A unique, random salt is generated and prepended to the encrypted file.

Example:

python script.py -e -p confidential.txt

Output:

Enter password for encryption:
Password must be at least 8 characters long.
Please choose a stronger password.
Enter password for encryption:
Confirm password:
File 'confidential.txt' encrypted successfully as 'confidential.txt.encrypted' using password-based key derivation.

3. Decrypt a File

Using Stored Key Method

python script.py -d -k <filename>.encrypted

• <filename>.encrypted: The path to the encrypted file.
• The script uses the key stored in secret.key.

Using Password-Based Key Derivation

python script.py -d -p <filename>.encrypted

• The script will prompt you to enter the password used during encryption.
• The salt is read from the encrypted file.

Example:

python script.py -d -p confidential.txt.encrypted

Output:

Enter password for decryption:
File 'confidential.txt.encrypted' decrypted successfully as 'confidential.txt.decrypted' using password-based key derivation.

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Examples

Encrypting and Decrypting with Stored Key

1. Generate a Key

   python script.py -g

2. Encrypt a File

   python script.py -e -k report.pdf

3. Decrypt the File

   python script.py -d -k report.pdf.encrypted

Encrypting and Decrypting with Password

1. Encrypt a File

   python script.py -e -p notes.txt

   • Enter and confirm your password when prompted.
   • Ensure your password meets the complexity requirements.

2. Decrypt the File

   python script.py -d -p notes.txt.encrypted

   • Enter the password used during encryption.

Graphics User Interface Options

The GUI provides the following features:

• Browse Files:

  • Easily browse your system to select the file you wish to encrypt or decrypt.

• Encrypt Button:

  • If you click Encrypt, the application will check if a secret.key exists in the root directory.
  • If no secret.key is found, the system will automatically generate one and place it in the root directory.
  • The selected file will then be encrypted using the generated or existing key.

• Decrypt Button:

  • Clicking Decrypt will require the encrypted file and the secret.key or password used during encryption.

• Password-Based Encryption:

  • Users can opt to encrypt files using a password rather than a key. A password dialog box will appear when encrypting, ensuring a secure and user-friendly encryption process.

Secret Key Generation

• When encrypting a file via the GUI:

  • If a secret.key is not already present in the root directory, the application will automatically generate a new one and save it there.
  • This secret key is essential for decrypting files later.

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Security Considerations

• Stored Key Method:

  • Key Security: The secret.key file must be kept secure. If an unauthorized person accesses this file, they can decrypt any files encrypted with it.
  • Key Backup: Losing the secret.key file means losing access to all encrypted data. Ensure you have a secure backup.

• Password-Based Key Derivation:

  • Password Strength Enforcement: The script enforces strong passwords to enhance security.
    • Passwords must meet the complexity requirements outlined above.
    • This reduces the risk of unauthorized access due to weak passwords.
  • Password Recovery: If you forget your password, the encrypted data cannot be recovered.
  • Salt Usage: A unique 16-byte random salt is generated for each encryption operation, enhancing security.

• General Recommendations:

  • Data Backup: Always keep backups of your original files before encryption.
  • Test the Script: Try encrypting and decrypting test files to familiarize yourself with the process.
  • Legal Compliance: Ensure that you comply with all relevant laws and regulations regarding data encryption in your jurisdiction.

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Limitations

• Large Files: The script reads the entire file into memory. Encrypting very large files may lead to high memory usage.
• Single-File Processing: The script processes one file at a time. Batch processing is not implemented.
• No Integrity Verification: The script does not include a mechanism to verify the integrity of the decrypted data (e.g., checksums or MACs).

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Future Enhancements

• Chunked File Processing:

  • Modify the script to handle files in chunks, reducing memory usage and allowing encryption of large files.

• Integrity Verification:

  • Include a Message Authentication Code (MAC) or checksum to verify data integrity upon decryption.

• Graphical User Interface (GUI):

  • Develop a user-friendly GUI using frameworks like Tkinter or PyQt5.

• Batch Processing:

  • Add functionality to encrypt or decrypt multiple files or entire directories.

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Troubleshooting

• "Password must contain at least one uppercase letter.":

  • Ensure your password includes at least one uppercase letter (A-Z).

• "Password must be at least 8 characters long.":

  • Enter a password that is at least 8 characters in length.

• "Passwords do not match":

  • Re-enter the same password during the confirmation prompt to avoid typos.

• "Incorrect password or corrupted file":

  • Ensure you're using the correct password.
  • Verify that the file was not altered or corrupted.

• "Decryption failed. Invalid key or corrupted file":

  • Confirm that you're using the correct key file.
  • Check if the encrypted file is intact and was not modified.

• "Key file 'secret.key' not found":

  • Ensure you've generated the key using python script.py -g before encrypting or decrypting with the stored key method.

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License

This script is licensed under the MIT License.

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Acknowledgments

• Cryptography Library: Utilizes the cryptography library for secure encryption and key management.
• Fernet Encryption: Implements Fernet symmetric encryption, ensuring that data is encrypted and authenticated.

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Thank you for using this encryption tool. Your feedback and contributions are welcome!