Is Network Security an Oxymoron?
For most of us, strong passwords, encryption, and keeping software updated delivers adequate computer network security. Extraordinary security measures demanded by kings, presidents, celebrities, dissidents, etc acknowledge that there is no privacy and no guarantee that digital property will be available, or private. Known sources of eavesdropping include automobiles, cell phones, computers, and considering the Internet of Things (IoT), the days of privacy are numbered. Benjamin Netanyahu, Prime Minister of Israel, recently commented that he is unwilling to use phones, cell phones, televisions, and computers when in his office.
A Lock Only Keeps Honest People Out
This point is self evident. The locks on your front door don't actually prevent a determined intruder from getting into your home. Bank vaults are breached and looted regularly. That's not to say that you can't spend millions of dollars fortifying your home with a concrete wall, moat, 24x7 armed security guards, and iron gates over all your windows and doors, for example.
Avoid AAA For A Serious Attempt at Private Communications
Telecommunications security uses the concepts of Authorization, Authentication, and Accounting (AAA). Who are you, what access do you have, and logs of your access; but, privacy requires plausible deniability. Belief that one could not have been party to the communication must exist. In other words, AAA must be avoided. The message must be anonymously placed offsite in an unremarkable location, i.e., in plain sight. For example, a "safe" in your bedroom closet is not a highly secure location for private content and neither is a bank vault as you are accountable for both.
Implement a Data Retention Policy
Implementing a data retention policy enables you to properly store and delete files. Make copies of any documents or files that you wish to keep, and delete any files that you no longer require.
###Destroy Used Electronics Physically destroy used computers, tablets, or phones thouroughly with a tool such as a hammer. Never transfer a used computer, tablet, or phone to a third party such as a garbage man. Never. The data on those devices remains retrievable even though you thought you deleted it or factory reset the device.
As a professional computer network engineer I recommend that you wholeheartedly believe that anything you digitize can and will be viewed by others. Implement a data retention and deletion policy. Your brain is the safest place to store sensitive information, followed by pen and paper. As for regular information, you are fine digitizing that and very basic security such as password protection is all you require.