Hi Johan, Have you checked the SHA256 sig with the iso? They can be found here: http://ftp.openbsd.org/pub/OpenBSD/5.0/<arch>/SHA256
If you don't have an OpenBSD installation already running to use the sha256 command, you can pick up tools over on sourceforge http://md5deep.sourceforge.net/ that can help you out with whatever platform you are running. Cheers, Jason. -- "Roads? Where we're going, we don't need roads" - Dr. Emmett "Doc" Brown