IF mobile network authetication is safer (or can be made safer) you could have device attached to your computer that would get a autheticity message back after it sends checksum or something throught the mobile network. 1. download update from internet 2. send checksum via attacheded device that uses mobile network and perhaps internet too 3. get verification to attached device via mobile network and to computer via internet 4. actually do the update... start building devices or do nice conversion unit for old mobile phones....

As long as you can get data from certain ip address/url you could download the update from 10 different addresses and then you could send it back to microsoft server (which verifies that it is authentic) and have your smart phone sent verification of safety of update and then your smart phone sends the OK to computer and then it updates. Or you could download the update to 100000 computers and then use beer-to-beer (joke) verifactionada and if enough verify the autheticity then perhaps accept it. You can say thank you MickeyMouseSoft if the idea posted above worked.