I noticed that passkey entry for BLE pairing is usually implemented by the device operating system outside the nrf_connect app. Is it possible to do passkey entry inside a mobile application's own GUI and have the mobile app software send the passkey back to the Nordic peripheral device? Or can the passkey only be handled by the phone's operating system?
Another possible method I was wondering about was whether it is possible to use a custom characteristic as a passkey? For example, after you pair with a device you have to write the passkey value to a custom characteristic. If the written value is the correct passkey, then other services are now discoverable or the read/write property of other characteristics are now active, etc. A vulnerability with this method could be sniffing if MITM protection was not active. But I also have an implementation question: Is it possible to change a custom characteristic's read or write properties after the characteristic is initialized?
