A Simulation-Driven BB84 Key Derivation Framework for Authenticated File Transmission over ESP32-Based LoRa Networks

The hybrid cryptographic file transfer uses BB84 Quantum Key Distribution (QKD) simulation, SHA-256-based key derivation, AES-256-GCM cryptography, and Long Range (LoRa) radio frequency communication. The BB84 simulation is carried out using IBM’s Qiskit with an Aer QASM simulator for quantum key distribution, basis reconciliation, and QBER calculation. This key is then converted to a 256-bit key using the SHA-256 technique and sent to Android phones via QR code scanning. Physical radio frequency communication is achieved using two ESP32 boards and LoRa RA-02 chips operating at 433 MHz. A Flutter application encrypts files using AES-256-GCM mode of operation with a 12-byte initialization vector and a 16-byte authentication tag, meaning each file has a fixed 28-byte overhead due to encryption. Encrypted data is sent in 200-byte blocks, utilizing sequence numbers, acknowledgements, retransmissions, and hardware CRC. Functional testing of message, text, image, and audio files demonstrates successful transfer and decryption. Testing with an incorrect key and altered ciphertext shows proper rejection of data based on authentication.