More than two centuries of elections in the United States have resulted in paper-based voting systems secured by a multitude of checks and procedures. New electronic voting systems require voters to trust computers and the people who program them, a trust that computer security experts say is unwarranted.

The subject is not hypothetical. Millions of voters will cast ballots on electronic machines today in the biggest test so far of the technology. To address security concerns, researchers are proposing new ways of voting that do not require voter trust in people or software. ...

One such solution, soon to be mandated in several states, is a voter-verified paper trail.

Dr. Rebecca Mercuri, a research fellow at the John F. Kennedy School of Government at Harvard, proposed a method that would require voting machines to produce paper printouts of the filled-in ballots, which would be checked by voters before being deposited in the ballot boxes. Only the paper ballots would be counted, bypassing the need to trust the voting machine.

An alternative is the "frog" voting system, proposed in a working paper released by the Caltech/M.I.T. Voting Technology Project in 2001. An all-electronic version of this approach — described by Dr. Rivest, Dr. Shuki Bruck of the California Institute of Technology and Dr. David Jefferson of Lawrence Livermore National Laboratory — would use two different types of electronic voting machines and a simple memory card, the frog. ...