I chose to use a H2 Database for the following reasons
- little footprint (size of library => 1.5 MB)
- has JDBC driver
- can encrypt database
- can create local databases
The file extension for H2 Databases is ".h2.db".
Here is a picture of the modelled database.
The LetterMan(ager) connects to the database using a hardcoded username ("SomeUserName") and user password ("A_Standard_Password"), this is because I wanted using the tool to be as simple as possible.
This way the user has only to remember one single password (the encryption password, no user name or account password to remember).
The database was designed using SQL Power Architect
The project file can be found here (you'll have to save it via right-click)