Rafeeq is spot on with regards to Digital Signing. But I am also curious about how the content is validated. The logs probably validate upon download but what if you wanted to validate after download to see if the content is corrupt? I'm still trying to research and understand this as well.
As far as validating MD5 values on an Intelligent Updater file, that is easy. You can see the MD5 hash online at Security Response. You then download the file and run an MD5 validation against it like my example below:
By clicking on "all", you will get a more complete list of MD5 values.