About the security of device file system

[marco5]

There will be some private data during app running, and we will write those data to the file system. 

We want to know if the device file system is sufficiently secure,  and if the file is encrypted, if not, how does Fitbit protect this data from being accessed by others?

[JonFitbit]

Your app has its own virtual filesystem. All device traffic is encrypted and the device itself is locked.