Add private key export support

- Add PRIVATE_KEY and DISABLED event types
- Add packet parsing for private key export responses
- Add export_private_key() method to DeviceCommands
- Add comprehensive unit tests
- Add BLE private key export example
- Update documentation with security notes

README.md

@@ -515,6 +515,8 @@ All commands are async methods that return `Event` objects. Commands are organiz
 | **Device Actions** ||||
 | `send_advert(flood=False)` | `flood: bool` | `OK` | Send advertisement (optionally flood network) |
 | `reboot()` | None | None | Reboot device (no response expected) |
+| **Security** ||||
+| `export_private_key()` | None | `PRIVATE_KEY/DISABLED` | Export device private key (requires PIN auth & enabled firmware) |
 
 #### Contact Commands (`meshcore.commands.*`)
 
@@ -601,6 +603,33 @@ meshcore.subscribe(
 )
 ```
 
+## Private Key Export Example
+
+Export your device's private key over BLE (requires PIN pairing and supported firmware):
+
+```python
+import asyncio
+from meshcore import MeshCore, EventType
+
+async def main():
+    # Connect to device over BLE with PIN authentication
+    meshcore = await MeshCore.create_ble(address="12:34:56:78:90:AB", pin="123456")
+
+    # Export the private key
+    result = await meshcore.commands.export_private_key()
+
+    if result.type == EventType.PRIVATE_KEY:
+        private_key = result.payload["private_key"]  # 64 bytes
+        print(f"Private key: {private_key.hex()}")
+    elif result.type == EventType.DISABLED:
+        print("Private key export is disabled on this device.")
+
+    await meshcore.disconnect()
+
+asyncio.run(main())
+```
+
+
 ## Examples in the Repo
 
 Check the `examples/` directory for more:
@@ -609,5 +638,6 @@ Check the `examples/` directory for more:
 - `serial_infos.py`: Quick device info retrieval
 - `serial_msg.py`: Message sending and receiving
 - `ble_pin_pairing_example.py`: BLE connection with PIN pairing
+- `ble_private_key_export.py`: BLE private key export with PIN authentication
 - `ble_t1000_infos.py`: BLE connections