Many people dont trust Dropbox, Google drive, Mega.co.nz for storing their private data. me neither

I want to ask what is the easiest way for encrypting/decrypting & syncing sensitive data of small volume to/from an external backup location (google drive, dropbox, external ssh server, ftp, email)

I mean i login to some computer, i run some script/program from USB flash to download my private documents & decrypt them. Then i work on them, save changes and these changes are uploaded back to external storage in encrypted form.

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A) https://www.boxcryptor.com

B) EncFS which creates an encrypted version of a files located in certain folder you speciffy.
There is EncFS for linux and EncFS for Windows.

Following is the Windows install guide for EncFS: Download app from above link or from this page attachment:
encfs.zip
(i dont guarantee anything, i just uploaded the archive downloaded from the author page as mentioned above.)

Then extract downloaded .ZIP and then download and install Dokan library only version 0.60 from there. Or as a backup there:
1st_DokanInstall_0.6.0.exe.zip

First you need to install Dokan, then run .exe file of EncFS called "encfsw.exe".

A Windows tray icon with "key" should appear. Click it and you can Open/Create new encrypted folder. There you select new folder which you will use for storing encrypted files. Once done, it will mount a new volume Drive (example: E:\) which will contain non encrypted version of files. Once you create, copy new files there, instantly an encrypted version of them is created in your basis folder.

So this way you can synchronise your E:\ contents with your dropbox, or set this drive as a Dropbox folder. USe another app to do the sync..