CakePHP Post action field filter

CakePHP Post action field filter

first: sorry for my bad english!
For security purposes, I'd like to filter all unallowed fields from the
$this->request->data Array.
E.g. my $this->request->data looks like this:
array(
'User' => array(
'password' => '*****',
'email' => 'asd@asdasd.de'
)
)
and I want to apply this Filter to the array above:
array(
'User' => array(
0 => 'password',
1 => 'email'
)
)
So all post-data's fields that are not in the filter-Array are being unset.
Thank you, L. M.