Experts recommend the machines not be used in elections unless they provide a physical paper trail.
Accidental bugs or intentional malicious code in e-voting machines could theoretically alter an election's results. ACM said that a paper trail will provide a way to double-check what's happening inside machines from companies such as Diebold Election Systems and Sequoia Voting Systems--a feat that would not otherwise be possible. Such systems are expected to be used by tens of millions of voters in the Nov. 2 U.S. election.