[galaxy-dev] uploading binary files checksum changes, Galaxy doing something to file?

Hi all, We tried to find something in the docs and mailing list no luck. We created a new datatype the is a straight subclass of Binary and then when we upload such a file in the Galaxy UI and check the checksums between the original file and the file located in the Galaxy database/files/... directory their checksums are different! What are we doing wrong? We simply want Galaxy to upload and no touch the file at all. regards, Leandro