BLE advertising packet formation using nordic stack

Question

I am working on A BLE beacon application to advertise data. I am using nordic nrf52 Development kit and nordic sdk s132. I am starting from the beacon exapmle provided by nordic. My question is how is the packet format of the message generated by that example: because as I could see from the code the only thing I am changing as a user the the manufacturer specific data field and as far as I know a BLE packet has this format But I do not see any function to calculate the CRC and In the included driver files I do not see any security related files Should I add these by myself and if so I need to know what is exactly handled by the nordic stack and is that I should add myself