hm..i downloaded all 3 programs but im lost...what now? how to i actually compare these values? :/
Click for small guide: http://i.imgur.com/lXOJG8X.png
then just copy / paste the resulting CRC from step 5 into 3ds.essh.co and see if you get a match.
(edit: The rom needs to be untrimmed for the CRC to match)
I use a program called 'Hashtab', it adds a 'File Hashes' tab in the file properties box.