ALLENTOWN, Pa. (AP) — Recount efforts after the presidential vote have highlighted major vulnerabilities in the U.S. election system long flagged by computer scientists.

Paperless electronic machines make it almost impossible to have a meaningful recount.

Such machines also raise the possibility that attackers could rig or disrupt an election without detection. And they are used by roughly 1 in 5 U.S. voters.

Green Party presidential candidate Jill Stein premised her recount effort in Pennsylvania on the need to ensure that the 2016 election wasn't tainted by hacking or fraud. There's been no evidence of hacking or fraud in the state, and a federal judge rejected her request.

Most Pennsylvania voters used antiquated machines that store votes electronically, without printed ballots or other paper-based backups. There was basically nothing to recount.

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