I had issues with my Kodi 17.6 on linux. I have noticed errors involving cryptography and ffi. Here is the procedure that I followed to fix it.
Open a Terminal and do the following:
sudo apt-get install build-essential libssl-dev libffi-dev python-dev python-pip
After its done then install cryptography for python
pip install cryptography
It will prompt to install update pip BUT DONT DO THAT IT WILL BREAK THINGS.