If you are using 0.x versions, I strongly recommended to upgrade to the current version. Until version 1.0-2 under cygwin no hash sums were build and under certain circumstances byte-by-byte-comparisons could fail. Due to this (former) defiences you might want to compare it to other programs, i.e. at Wikipedia.org/wiki/freedup.
Starting with version 1.0-4 all packages on this page are signed.