🔐 RSA Digital Signature Generator and Verifier

This project implements a complete RSA-based digital signature system using OAEP padding and SHA3-256 hashing, fully written in Python 3 and without external cryptography libraries.
It includes both a command-line interface and a Tkinter GUI, designed for educational and academic use.

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🧠 Overview

The system can:

• Generate RSA key pairs (2048 bits);
• Encrypt and decrypt files using OAEP and SHA3-256;
• Digitally sign and verify text or binary files;
• Operate through GUI or terminal menu;
• Optimize decryption using the Chinese Remainder Theorem (CRT).

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⚙️ Project Structure

├── key_generator.py # Prime generation (Miller-Rabin + trial division) ├── rsa_keypair.py # RSA key generation and CRT optimization ├── rsa_oaep.py # OAEP padding and RSA operations ├── signature.py # Digital signature and verification ├── interface.py # Graphical interface (Tkinter) ├── main.py # Command-line interface └── README.md

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💻 Requirements

• OS: Linux (Ubuntu 20.04+ recommended)
• Python: Version 3.10 or newer
• Standard libraries used: hashlib, math, secrets, base64, tkinter

No external libraries are required.

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🚀 How to Run

1. Clone the repository

bash git clone https://github.com/Isaaacsc/P2_Seg.comp.git cd rsa-signature-tool 2. Run with graphical interface bash python3 interface.py 3. Or use the command-line menu bash python3 main.py 🔧 Features Key Generation: 2048-bit RSA with Miller–Rabin primality test

OAEP Padding: Secure against chosen-ciphertext attacks

SHA3-256 Hashing: Ensures strong message integrity

CRT Optimization: ~75% faster RSA decryption

Error Handling: Detects invalid keys, corrupted or tampered files

🧪 Example Usage Generate keys:

bash python3 main.py → Select option 1 to create public_key.txt and private_key.txt.

Sign a file:

bash python3 main.py → Choose option 4 and enter the file name (e.g., document.txt).

Verify signature:

bash python3 main.py → Choose option 5 to confirm authenticity.

👥 Authors Name ID Role Isaac Silva - Isaaacsc Gabriela Costa

📚 References RFC 8017 — PKCS #1: RSA Cryptography Specifications (v2.2)

Python Docs — hashlib module

Wikipedia — RSA cryptosystem, OAEP, Miller–Rabin test

🧾 License Developed for the course CIC0201 – Computer Security. Free for academic and research purposes.