greedann / assymetric-file-encryption

File encryption app

Asymmetric file encryption

Introduction

This repository contains several Python scripts that implement various cryptographic functions. Most of the functions are cross-platform, but some are only available for Linux.

Features

• Digital signature generation
• Private key sharing
• Encrypting files with digital signature
• Encrypting files with a password
• File decryption with a private key or password
• Disk encryption/decryption (Linux only)
• Recovery of private key with a preset number of parts

Installation

Dependencies

Python3

To run the application locally you need to clone the repository.

git clone https://github.com/greedann/Assymetric-file-encryption.git 
cd Asymmetric-file-encryption

Create virtual environment and install requirements

python3 -m venv venv
source venv/bin/activate
pip install -r requirements.txt

Now you ready to go

Usage

Generate certificate

First, to use the cryptographic functions, you need to generate your digital signature and its private key. This can be done as follows:

python generate_certificate.py

You now have your own certificate that you can use to encrypt your data.

Encrypt file

To encrypt a file, run the command below

python encrypt_file.py <filename>

Where filename is the name of the file in the current directory or the full path to the file. After the command is executed, an encrypted file with the format .bin will appear.

Encrypt drive

To encrypt a drive, run the command below

python encrypt_drive.py <device>

Where device is the name of the disk you want to encrypt. After running the command, your disk will be encrypted.

Decrypt file/drive

For decryption the procedure is very similar, but you need to change encrypt to decrypt in the commands for encryption. The arguments remain the same.

Private key restore

If you split your private key into several parts when creating a digital signature, it is possible to restore it. To do this, you need to collect the minimum number of parts (specified at creation) and place them in the certificate directory. And then execute the command

python restore_private_key.py

If the parts of the key were correct and were sufficient, the private_key.pem file will appear in the certificate directory, containing your original private key.

Technical details

File encryption

Files are encrypted using RSA symmetric encryption algorithm and session key. The session key in turn is encrypted using the public key and AES algorithm in GCM mode and stored in the encrypted file. To decrypt the file, a private key is used to decrypt the session key, and then the session key decrypts the file itself.

Disk encryption

For disk encryption “full disk encryption” is used. That is, not only the data itself is encrypted, but also the partition data. First all data is copied from the disk and then encrypted as a file. After encryption, the data is written back to the disk. When decrypting, the process is reversed.

Key recovery

The possibility of data recovery in case of private key loss is realized in 2 ways:

1. Through private key recovery from parts using Shamir's scheme
2. By restoring a file using a password. The session key is encrypted using a password when encrypting a file and is saved with the file. When decrypting the file, the user must enter the password that will be used to decrypt the session key.