PITTSBURGH (KDKA) — There’s been a lot of talk over the past few weeks about the presidential election being rigged. But is it really possible to tamper with voting machines in Pennsylvania?

“That, of course, is possible because it’s a computer,” Dr. Mike Shamos, an election expert from Carnegie Mellon University, said.

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Emphasis on the word “possible.”

“We have not seen any evidence that anything has been compromised since we had the machines,” Allegheny County Director of Elections Mark Wolosik said.

There are a lot of reasons for that. Let’s say you could break into the machines and reprogram them to favor a candidate.

The first issue,” Wolosik says is, “They are an island unto themselves. They are not connected to any other machine.”

So any manipulations would have to be one machine at a time, which Dr. Shamos estimates would take 15 minutes per machine, with 4,500 machines.

“To do it for all the machines in the county would take four months,” said Dr. Shamos.

It would also have to be done undetected in a warehouse that is under surveillance 24 hours a day, seven days a week, 365 days a year.

Over the past week, the election machines have moved from the warehouse to the polling places.

“Prior to leaving our warehouse, they are sealed with an individually numbered seal that is recorded,” Wolosik said.

Then, on the morning of the election, the poll workers compare the number to the seal.

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“If there are any discrepancies, they are not to use that machine and to call our office immediately,” said Wolosik.

Once the machine is set up and ready, the poll workers have it print out a report to prove no votes have been cast on the machine. After the day of voting is over, the poll workers hit print again, three times.

They are then signed, and Wolosik says, “Posted at the polling place, given independently to another polling place official and also returned to us.”

The copy that comes to the county is the official result and is hand-tallied a couple of days after the election for the official total. But there’s also a chip in the machine that is pulled after the vote and delivered with the paper result.

“Those are modules that are stuck into a machine one by one, very quickly, and you’re able to add up the total vote for the entire county,” Dr. Shamos says.

As far as hacking or manipulating the voter registration rolls, to have any impact on a race, thousands of voters would have to be involved. And if, say, registrations were canceled, the impact would be noticed immediately.

“This would occur all over the state beginning with the opening of polls on Election Day, and there would be screaming all over the place,” says Dr. Shamos.

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The security doesn’t end immediately after the polls closed and votes are totaled.

After the voting is done, the machines return to the warehouse and are not touched for 20 days in case there is an issue with any results. After that, the workers start getting them ready for the next election.

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One other safeguard – while voting is going on, an independent accounting agency randomly selects a voting machine somewhere in the county and tests it to see if there’s any Trojan horse software running on it.