How can I stop someone from hacking in to my Arduino via Bluetooth? I am using an HC-05 bluetooth Module. How can I stop someone from pairing with my device by brute forcing the key? Failing that, and if someone does pair with my device, is there a way to authenticate the user? I was thinking of salted hash with a shared secret key. Is there anything better?
Configure your Bluetooth module to AT Command Mode

Then use AT+PIN Command to change the default PAIRING PIN of the Bluetooth Module.

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