Upload & Sell: Off
Here is some background for you:
For someone responsible for important data, I'm more than a bit surprised that you do not know about this extremely important phenomena. It does indeed exist.
Can checksum's be used to protect our digital archives? If yes, how to get started in such a manner?
If data changes due to dormancy and slow changes in the charge on a disk platter or SSD, a smart storage system will notice that. There's even a checksum link right from your wiki article to get you started. A decent storage controller does a lot more than that. Thing is, all this is expensive compared to the cheap yet dumb external drive, which does have its place in smaller systems, but won't do any of the constant monitoring to keep data fresh.
Bottom line, you have to use the right hardware. It begins on the low end with proper server RAID controllers (LSI, 3Ware, Areca, search about their RAID 6 offerings), and it ends with Enterprise Storage Systems like EMC, which are massively redundant and geographically multi-hosted, and run on hardware only large institutions can afford. Short of Yellowstone's caldera blowing up and covering the Midwest with 12 feet of ashes, we probably won't lose the data I am responsible for, but then we'll have different problems .