Md5 checksum?

Im trying to modify a game file but it will result a black screen.
Did some changes and leave it at the same size.
Its an XML file i also tried to remove a space and added it some where else in the XML.
After that the md5 hash changes and the size stays the same.
But the XML stays correct i used notepad ++
So im thinking that there is a md5 checksum in the eboot that is signed with 3.70 keys

So without 3.70 keys there is nothing possible too make any changes?