Question about Safe database

Hi , I’ve been searching for a method to achieve it ,
and my main goal is to let the data which is very important
like user name , password , inventory stuffs , to be uncheatable
since I would let the player start their own listen server , it’s impossible to control everything
but at least the inventory , and login system .

my first thought is to run a php server to handle it , but after this thread
it’s told to be unsafe and very slow … so i’ll forget about it .

here’s my question
Is it possible to create a dedicated server , which is built only for data transporting
and the listen server could fetch the data they want , save , and create from their client side ?
and the server still be well secure …

and Is it possible to achieve something like that only by BP ?
anything would be helpful , thanks

(update : 8/28)
I’ve search for some days and realize that the problem is about my lack of skills
No C++ means I’m can only do little on this
I’ll try using a cheap way , the JSON query plugin with php , I hope it work
it should , but not very wise