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).