RIVERSIDE -- California's chief elections official said she can neither approve nor block a proposed public attempt to "hack" local voting equipment, but warned that the test, as now envisioned by a county supervisor, wouldn't prove the machines' security.

Following a group's repeated protests that Riverside County's touch-screen voting machines are vulnerable to manipulation, Supervisor Jeff Stone challenged voting activists in December to find a computer scientist able to manipulate the vote totals or counting mechanisms stored on one of Riverside County's voting machines.

On Jan. 3, Stone wrote to outgoing Secretary of State Bruce McPherson, asking him to review the test to ensure that it wouldn't run afoul of the law. New Secretary of State Debra Bowen, a former chairwoman of the Senate Elections Committee, took over Jan. 8.

Bowen answered Stone's letter last week, saying Stone had focused the test too narrowly on the specter of a rogue citizen trying to hack into the machine while in a voting booth during an election.

Stone first floated the idea at a Board of Supervisors meeting in early December to Maxine Ewig, a Temecula resident representing Save R Vote, a loose-knit group of Southwest County activists that has frequently questioned the security of the Sequoia Edge II and other touch-screen voting machines.

Stone cast the idea as a rhetorical "thousand-to-one" bet that a computer scientist hired by Save R Vote wouldn't be able to load malicious software onto the machine or otherwise fiddle with the vote totals stored in its memory. At the time, Stone and Ewig discussed few specifics.

Stone later laid out the scenario of a rogue voter in his Jan. 3 letter, saying the hacker should approach the machine only as a voter would, and hack into it using only tools concealed in normal-sized pockets. Bowen called Stone's idea for the test "overly narrow."

"Voting equipment is subject to tampering in a wide range of settings," Bowen wrote. "As I understand the test you've constructed, it wouldn't address the larger issue of whether someone who has access to the voting equipment before the polls opened or after they closed could interfere with the proper use of equipment."

Stone, who was traveling to Washington, D.C., for a national conference for county government officials, couldn't be reached for comment. In earlier comments about the security display, he had criticized Save R Vote as undermining voters' confidence in the reliability and security of the machines. He issued the challenge in large part, he said, to buttress that confidence by allowing the machines to withstand the scrutiny.

Stone's chief deputy said the supervisor is still willing test a machine with the conditions he described. A test of the sort envisioned by Save R Vote should be overseen by a "blue ribbon" panel of former public officials who are now reviewing a broad range of election procedures in the county, said the deputy, Verne Lauritzen.

Hacking one of the machines during a window of more than 15 minutes would depend on additional security breaches that aren't specific to the machines' software -- for example, their storage area being left unlocked or their seals being compromised, Lauritzen said.

"Any computer techie can do anything they want with a machine, given enough time," Lauritzen said.

Stone has said he would ask the full Board of Supervisors to approve the public test of the voting machines. In her letter, Bowen said she wouldn't stand in his way.

Tom Courbat, a Murrieta resident and coordinator for Save R Vote, lauded Bowen's critique of the hack test. Courbat and other members of Save R Vote have repeatedly criticized Stone's conditions as too narrow.

Bowen said -- and Courbat echoed -- that allowing the test to go forward with Stone's conditions would prove little and possibly even give voters a "false sense of security." Bowen, too, has expressed skepticism of the voting machines in the past, and has called for tougher security measures though she has stopped short of calling for wholesale replacement of the thousands in use across the state.

Fewer than half of California voters have used the touch-screen machines in recent elections, whereas most of the rest use paper ballots that are marked in pencil and scanned by optical readers.

- Contact staff writer Chris Bagley at (951) 676-4315, Ext. 2615, or cbagley@californian.com.