S17 Secure Wireless Protocol

A secure, encrypted wireless communication protocol for embedded systems. Built for STM32F103 + NRF24L01+ with AES encryption and intelligent networking.

What is S17?

S17 is a secure tactical data link system providing encrypted wireless communication between embedded devices. It features time-slotted access, frequency hopping, and military-grade security for applications requiring reliable, secure communications.

Integration

Project Structure

your_project/
├── S17/                 # This library (as submodule)
├── hermes/             # NOC device (master)
├── homa/               # Tactical node (slave) 
├── belfhym/            # Tactical node (slave)
└── shared_libs/        # Common utilities

Adding to Your Project

1. Add as submodule:

   git submodule add <repo> S17

2. Include in Makefile:

   include S17/Makefile

3. Create configuration (S17_config.h):

   #define S17_DEVICE_ID         S17_NOC_HERMES
   #define S17_DEVICE_ROLE       S17_TIMING_MASTER
   #define S17_NETWORK_KEY       {0x4A, 0x75, /* ... */}

4. Initialize in main:

   s17_init(&config);
   s17_start();

Basic API

• s17_init() - Initialize with device configuration
• s17_start() - Begin secure communications
• s17_send() - Send encrypted message to device
• s17_broadcast() - Broadcast to all devices

Security Model

S17 implements a multi-layer security architecture:

Encryption: AES-128 with CTR mode for all messages Authentication: Message authentication codes prevent tampering
Replay Protection: Sequence numbers prevent replay attacks Key Management: Hierarchical key system (RMK → NMK → TEK) Perfect Forward Secrecy: Session keys rotate every 15 minutes

All communications are encrypted by default - no insecure modes available.

Device Types

NOC (Network Operations Controller): Master device controlling network timing and key distribution TN (Tactical Node): Field devices receiving commands and sending telemetry

Network Architecture

Time-divided access prevents collisions:

• Slot 0: NOC beacon and commands
• Slot 1-2: Node telemetry slots
• Slot 3: Shared/emergency slot

Frequency hopping across 5 channels provides anti-jamming capability.