I'm focused mainly on :

1-  Postgresql  database : Installation from a customized source code  & encryption of the DB cluster with data-at-rest encryption .

2- Security of data & connections : the database encryption , SSL Certificates(ROOT,Intermediate,trust-chain, Server & Client) & also creating SSLSockets  for both the server & the client using customized provider such as Bouncy Castle with FIPS mode.

3- GUI building using JavaFX & Jfoinex . 

4- The Ubuntu Server both installation & configuration (creating users,firewal, netplan networking).