The dirty little secret about computer security is that absolute security is absolutely impossible. If a competent hacker has physical access to a computer, or just it's storage device, it's precious private data can almost always be retrieved. Even if the data is encrypted. As this page is being written, the FBI has started retrieving encrypted data from iPhones without any help from the phone's owner or manufacturer. This is relatively simple because, with symmetric encryption, the kind used to encrypt an entire device, the same "key" is used for both encryption and decryption of the data. Therefore, the key must be available when the device starts up, or none of that data will be available to anyone. Either the key must be stored somewhere on the device (or in another easily accessible "safe" place) or, it must be stored in the brain of the user (to be entered during startup). It may be obscured, but a stored key can usually be recovered, as in the case of the iPhone, above. When memorized, it can be recovered by legal compulsion or even, in extreme cases, by torture.
This why a portable device, such as a smart phone or laptop, is one of the most foolish places to keep sensitive information (either one's own or another's). The device may be easily lost, stolen or legally confiscated. And in all of these situations the private data IS recoverable, with potentially disastrous results! A much safer solution is to keep all data on a server and to access it from a portable device only when needed. But, no information should ever be stored on somebody else's server, somewhere in the Cloud. The Cloud is, without any doubt, the most truly insane place to store any information. At some point, everything stored in the Cloud is guaranteed to be stolen or misused without the knowledge or informed consent of the owner of the information. In fact, the Cloud is designed to steal the data of it's users, for the financial benefit of the owners of it's massive server farms. Those we call the Big Data Bandits.
To be continued . . .