> I was working on a ERP system and finally, concluded.
> I used firebird as database. I created a new password for admin. created a new user and password.
> I installed on a client machine, the erp.fdb file and the application.
> They were using and were happy.
> Now, I came to know that, one guy in the client place, stole the erp.fdb and tried several passwords and did not get it, so, he installed a firebird on his computer and copied the erp.fdb and opened it with firebird default password, and stole the entire db design.
>
> how to protect from this kind of things.

Physical security of the database file.

> How to make sure, that the database cannot be copied?

See above.

There is no other way, everything else can get circumvented - usually
quite easily.

Pepak