It's probably small bits & bobs placed to please this and that opertor. Probably best way would be to get the tools to make an image and use them to open those .bin and compare them Do you remember what kind of error it throws in that case? Is is a 'security error' or a 'downgrade disallowed'? The flashing verification is like: if (version1 > version2) and (swcert1 > swcert2) and (time_of_day > swcert1) and (other tests) then flash_version1 else exit_with_error If that verification fails the only way to allow 'downgrade' is to use a rd certificate, but that has been available only in devices used internally in Nokia for testing.