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Messages are framed with CRC-16, AES-256 encrypted, and exchanged using an RTS/CTS handshake to maximize link reliability.\n\n---\n\n## Table of Contents\n\n1. [Overview](#overview)  \n2. [Features](#features)  \n3. [Architecture \u0026 Design](#architecture--design)  \n4. [Requirements \u0026 Dependencies](#requirements--dependencies)  \n5. [Installation](#installation)  \n6. [Usage](#usage)  \n7. [Encryption \u0026 Security](#encryption--security)  \n8. [Protocol Details](#protocol-details)  \n9. [Error Handling \u0026 Diagnostics](#error-handling--diagnostics)   \n10. [License](#license)  \n11. [Author](#author)  \n\n---\n\n## Overview\n\nSDR-Chat turns a USRP SDR into a secure text chat device. It combines Python for control and GUI, C for performance-critical modulation/demodulation, and UHD for radio interfacing. \n\n---\n\n## Features\n\n- **FSK Modulation \u0026 Demodulation**  \n  FSK at configurable baud rates.  \n- **AES-256 Encryption**  \n  Encrypting every message payload.  \n- **CRC-16 Error Detection**  \n  Catching transmission errors before decryption.  \n- **RTS/CTS Handshake**  \n  Simple link-establishment protocol to avoid collisions.  \n- **CLI \u0026 GUI Frontends**  \n  Lightweight terminal mode or a minimal GUI.  \n- **Configurable Parameters**  \n  Frequency, gain, baud rate, preamble length, and more via flags or config file.\n\n---\n\n## Architecture \u0026 Design\n\n```\n+-----------+      +-----------+      +------------+      +----------+\n|  main.py  | \u003c--\u003e |  C module | \u003c--\u003e |    UHD     | \u003c--\u003e |   SDR    |\n|  (Python) |      |   (FSk)   |      |   drivers  |      | hardware |\n+-----------+      +-----------+      +------------+      +----------+\n      ^\n      |\n  +--------+\n  | GUI UI |\n  +--------+\n```\n\n---\n\n## Requirements \u0026 Dependencies\n\n- **Hardware**  \n  - Ettus USRP B200mini or B205mini (other UHD-compatible radios may work).  \n- **Software**  \n  - Python 3.8+  \n  - UHD drivers \u0026 firmware  \n  - C compiler (GCC/Clang)  \n\n---\n\n## Installation\n\n1. **Clone the repo**  \n   ```bash\n   git clone https://github.com/roeelupo/sdr-chat.git\n   cd sdr-chat\n   ```\n2. **Build the projet**  \n   ```bash\n   pip install .\n   ```\n\n---\n\n## Usage\n```bash\nexport AES_KEY=$(openssl rand -hex 16)\nsdr-chat --help\n```\n\n### CLI Mode\n\n```bash\nsdr-chat --aes-key $AES_KEY\nsdr-chat --aes-key \"d76df8\"\n```\n\n\n\n### GUI Mode\n\n```bash\nsdr-chat --aes-key $AES_KEY --gui\n```\n\n---\n\n## Encryption \u0026 Security\n\n- **AES-256-CBC** for payload confidentiality.  \n- Each message includes a random IV—prepended to the ciphertext.  \n- Pre-shared key or config file specifies AES key.  \n\n---\n\n## Protocol Details\n\n| Field       | Size            | Description                       |\n|-------------|-----------------|-----------------------------------|\n| Preamble    | 16 bits         | 0xAA55 pattern for sync           |\n| Header      | 8 bits          | Payload length \u0026 flags            |\n| Payload     | 0–256 bytes     | AES-encrypted message             |\n| CRC-16      | 16 bits         | CRC-16 of header+payload          |\n\n- **FSK frequencies**: mark = +5 kHz, space = –5 kHz offset by center frequency.  \n- **RTS/CTS**: short control frames before data exchange to reserve the channel.\n\n---\n\n## Error Handling \u0026 Diagnostics\n\n- **CRC Failures**: Logged to console/GUI; peer will automatically retransmit.  \n- **Timeouts**: If no CTS received within 500 ms, CLI retries handshake.  \n\n---\n\n\n## License\n\nDistributed under the **MIT License**. See [LICENSE](https://github.com/RoeeLupo/sdr-chat/blob/master/LICENSE) for details.\n\n---\n\n## Author\n\n**Roee Lupo**  \n– Self-Proclaimed Engineer \u0026 SDR Enthusiast  \n– [GitHub](https://github.com/roeelupo) · [roeelupo@roeelupo.com](mailto:roeelupo@roeelupo.com)\n","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Froeelupo%2Fsdr-chat","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Froeelupo%2Fsdr-chat","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Froeelupo%2Fsdr-chat/lists"}