how to skip the encrypt flag in a encrypted file on IRP_MJ_READ in MINIFILTER driver!!!

hi all,

i’m writting a online encrypt minifilter driver with win2003 ifs ddk (sp1),i
add a 96 bytes encrypt flag at last of the encrypted file,i want to skip
flag when user’s program read it.how can i modify the irp_mj_read’s
parameter to do this?