Rumours are coming out that the Department of Homeland Security marked all the ballot papers with a IR watermark and also lodged each ballot paper on the QFS blockchain, to prevent tampering and so that everyone can check it themselves (this is the beauty of Blockchain technology if you understand how it works).
I think the official mail-in ballots that were mailed out by DHS were all water-marked. There are dots all over the pages that jump out at 640nm wavelength. (credit - perrarm2)
From another user - credit to Landcruzer94
I follow the crypto world a little bit, mainly ways to use blockchain to combat counterfeiting. In 2017/18, a company called INPI Asia developed a way to mark an item with an invisible identifier, everything from metal car parts to paper goods. This code could be linked to a blockchain to establish authenticity. There's not much info on it, but some governments have adopted it to secure their own documents. EDIT: It was the government of Jakarta that adopted this for all of their documents.
A better representation of how it works:
the code is transferred to the paper before the ballots are even printed.
Earlier this year, USPS quietly revealed some patents in blockchain voting that took some by surprise...
"A separation of voter identification and votes to ensure voter anonymity is the principal feature of the solution. The votes are stored on a blockchain attested by election officials. Obviously, this patent is too late to be developed and deployed for this election."
This could be the link. Why would we push SO hard for blockchain voting and not tout it just before the election? If you wanted to set the trap you wouldn't talk about it. These ballots could be blockchain voting in disguise, just not the way I thought they would be. EDIT: this actually makes the most sense. In an ideal world you'd push for a blockchain system that links you with how you vote that is tamper proof, Voter ID of the grandest scale if you will. Dems have been allergic to that forever and this is a sneaky way to integrate it.
Far fetched, but possible.