The way I've done is create a table wich I use as the application registry. (two fields "Key" and "Value"
In that table I store several values that have to do with app operation, and also an encription key (call it password if you prefer).
The key itself is encripted and in binary, so if you look at the DB you will find a huge string with 0 & 1 wich if you try to translate would have no meaning.
During runtime I decript the key and then using the key I decript whatever I need.
It may not be perfect, but at least if someone peeks DB or code would have some more guessing work to do.