Store encrypted files on Google Drive

 We'll use the Grive Linux client for Google Drive and EncFS to create a 'safe' in the cloud, inside Google Drive and mount it locally:

1. Install Grive

sudo add-apt-repository ppa:nilarimogard/webupd8
sudo apt-get update
sudo apt-get install grive

2. How to use
Create a working folder :

mkdir ~/grive
cd ~/grive/

Initial setup will require an authorization token from Google. Paste the link generated by the following command into the browser, get the token and paste it into the application

grive -a

Synchronization of all the files in the cloud:

grive

3. Create an encrypted safe
For this I've used EncFS to create an encrypted filesystem inside the folder for the Google Drive:

apt-get install encfs
mkdir -p ~/grive/safe
mkdir -p ~/safe

Mount the encrypted safe to a decrypted folder (open the safe). If EncFS cannot find a filesystem at the specified location, it will create a new encrypted file system there.

encfs ~/grive/safe/ ~/safe/

I've used the paranoia mode for the initial setup - AES-256, PBKDF2, 160 bit salt, External IV Chaining (More details about the settings in the man page).
To verify that it was mounted correctly:

df -hT
encfs        fuse.encfs  455G  232G  200G  54% /home/liv/safe

Test the whole setup:

cd ~/safe/
echo "secret" > test.txt
cat test.txt
secret
ls ~/grive/safe/
pr6KT6wBszfvBqNLIo2pPliZ

Unmount the encrypted volume (close the safe):

sudo fusermount -u ~/safe

Notes
1. EncFS uses a file named .encfs6.xml to define the encrypted storage settings. This hidden file is not synchronized by Grive. 
Solution: get a patched version of Grive or rename the file and store it on Google Drive. 
After synchronizing Grive on another machine, rename the encfs6.xml file to .encfs6.xml.
2. Problem:
fusermount: failed to open /dev/fuse: Permission denied
Solution:
usermod -aG fuse
reboot

References
EncFS Encrypted Filesystem
Grive - Open source Linux client for Google Drive
Synchronise hidden files other than .grive*