CppCrypt

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Description

This is a learning project about the Diffie-Hellman (DH) key-exchange and Advanced Encryption Standard (AES).

Goal of the project is to implement following Features

• Encrypt and save text files in an encrypted state, as well as vice versa
• Send text files via TCP using (EC) DH for key exchange followed up by AES for encryption

Content description

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The subdirectory prim_roots contains a module named primitive_roots for verification of prime numbers and calculation of their primitive roots and is used for DH.

The subdirectory aes contains a module named pyaes which contains function definitions for key-expansion from key to round keys, as well as encryption and decryption of sixteen bytes, formatted as 4x4 matrix.

The aesify.py script encrypts and decrypts textfiles.

The ecdhify.py script exchanges keys per ECDH and sends a via AES encrypted file from host to client afterwards.

Development Environment

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• Operating System: Fedora Linux 41 (Workstation Edition)
• Python: 3.12.3
• g++ (GCC): 14.2.1 (Red Hat 14.2.1-7)

Dependencies

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build           1.2.2.post1
numpy           2.2.4
packaging       24.2
pip             25.0.1
pybind11        2.13.6
pyproject_hooks 1.2.0
setuptools      78.0.1

Installation

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To install dependencies for building the C++ extensions (on Fedora) run

sudo dnf install python3-devel

To install the necessary packages from the Python package index run

pip install -r requirements.txt

To build the C++ extensions run

python -m build cryptology/aes/ -n -w

To install the extensions as Python packages run

pip install cryptology/aes/dist/*.whl

Usage of aesify.py

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Given a textfile called lore.txt containing plaintext

Encryption

After running

python aesify.py -en lore.txt crypted_lore.txt 

you will be prompted to enter a passkey, which is expected to be expected to be 16 hexadecimal numbers in the range between 0 and FF separated by commas, like for example

0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f

Decryption

Print

To just print the contents of a previously encrypted file into the terminal run

python aesify.py -de crypted_lore.txt -p

Save to txt

To save the contents of a previously encrypted file as plaintext run

python aesify.py -de crypted_lore.txt decrypted_lore.txt

Usage of ecdhify.py

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Run as host:

python ecdhify.py h

Run as client:

python ecdhify.py c

License

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This project is licensed under the MIT license.