How to Prevent Magic Pens ?

" During the super day, the people who have decided to vote, reach the polling place to cast theirs votes following two ways:

1) Voting through Voting Machines

2) Voting through Paper Ballots which will scanned by VM

Usually older voters prefer cast theirs own vote through classical paper ballot rather then "complicated" electronic voting machineries; for that reason they ask to the pool worker the paper and the pen. The pool worker, who is a volunteer (so, he may be "sponsored" by some political people ?? ) say to the voter:

' Here we go! This is the paper ballot, and this is the MAGIC PEN. You know, the polling worker to the voter, today thanks to these machines the privacy is the most important issue to respect, so they build this MAGIC PEN with a particular ink that only the voting machine can read. So let use it like a normal pen and then put your ballot inside this slit (Voting Machine's Scanner). The Voting Machine will read through its special sensors your vote and it'll sent your casted vote directly to the central.

The unwitting old voter will put some invisible signs on the ballot using the fake PEN and, at the end of the fake voting phase he'll try to cast his vote through the voting machine's scanner and he'll go away. The Voting Machine's scanner unable to read the paper will reject the paper, the pooling worker will refill the ballot with his favorite runner and here we are ! Another faked vote. "