How can any one person be sure that a completely paper based voting system is working fraud-free in a country with hundreds of millions of people? How can you

How can any one person be sure that a completely paper based voting system is working fraud-free in a country with hundreds of millions of people? How can you be sure the financial system you use is working? >nobody will ever be able to contest it. See blockchain. If everyone has a copy of the vote registry, then they can contest it if things don't match up.