About 10 years ago I worked for a while for a company that developed electronic games for the casino industry. At the heart of every game is a random number generator that feeds numbers to the games. The games themselves are fully stateful, so if you reset a game and give it the same sequence of random numbers (and play your moves identically) then it should result in the exact same outcome.

The RNG's themselves are highly secure since the play of every game depends entirely on them. IIRC, there are only two companies that have RNG's certified for use in Las Vegas (at least at the time I was working for this company). An RNG is essentially a small box with a power cord, a serial connector, and a locked panel to get inside it. whenever a game that's hooked up to the serial port reads from it, it gets a new random number. If power is lost or if the RNG is opened up then the device immediately locks itself down (and possibly if the data signal on the serial port is lost as well, I forget). Once the device is locked down it has to be reset by the gaming commission, who are the only ones with the appropriate codes to do so.

The gaming commission also has the ability to audit the RNG's, which let's them generate a complete list of all the random numbers that the device has generated. And since the games themselves are stateful, it means that they can replay entire game sequences if necessary in order to verify the outcome of a game.

At first it surprised me how sophisticated & secure these RNG's are and that voting machines aren't anywhere near as secure. But then it occurred that billions of dollars a year rely on the security of the RNG's, while politicians rely on the results of voting machines...