I believe there needs to be the following 3 security measures put into place:

a) Option to secure all files/folders and documents with a dual (two separate yet different) passwords. [ In otherwords, two different passwords are required to open a file/folder ].

b) The capability to also make file/folders invisible to unwelcomed visitors.

c) Text Encryption for writting secure documents.

You might want to look at some of the GPG programs available. I installed a set of Service menu items for encrypting/decrypting files and selections.