External password test

[JAV-ISH]

Hi,
I have some external services around my forum, but on an other server, with no posibility to connect to the database vom vB 3.0.

So I need a PHP-file, which has a function to check password/username, given from extern via post, and returns just 0 or 1 via "echo()"

To prevent a usage as bruteforce-file, there has to be a third parameter, a special password to validate that it is me, who wants to check.

function(specialkey, password, username) returns bool

Is this possible?

best regards,
flo