Paperless electronic voting machines used throughout ... much of the country cannot be made secure," according to draft recommendations issued this week by a federal agency that advises the U.S. Election Assistance Commission. The assessment by the National Institute of Standards and Technology, one of the government's premier research centers, is the most sweeping condemnation of such voting systems by a federal agency. NIST said that voting systems should allow election officials to recount ballots independently from a voting machine's software. The recommendations endorse "optical-scan" systems in which voters mark paper ballots that are read by a computer and electronic systems that print a paper summary of each ballot, which voters review and elections officials save for recounts. NIST says in its report that the lack of a paper trail for each vote "is one of the main reasons behind continued questions about voting system security and diminished public confidence in elections." The report repeats the contention of the computer security community that "a single programmer could 'rig' a major election." NIST says that voting systems should not rely on a machine's software to provide a record of the votes cast. Some electronic voting system manufacturers have introduced models that include printers to produce a separate record of each vote -- and that can be verified by a voter before leaving the machine -- but such paper trails have had their own problems. Printers have jammed or otherwise failed, causing some election directors to question whether a paper trail is an improvement.