In addition, the handhelds will be equipped with Global Positioning System mapping information to help census takers find addresses. And to meet the Census Bureau's strict privacy requirements, all the data collected on the handhelds will be encrypted and census takers will be locked out of the operating system to prevent any private uses of the devices, Murray said.

Census Bureau officials have said the use of the handhelds will result in greater efficiency for field workers who traditionally have carried paper address lists. They also expect the project to save the government millions of dollars by shortening the time it takes workers to gather data, improving the information's accuracy and reducing the need to process paper census forms.

Harris has estimated that the new technology could enable the Census Bureau to save $1 billion in operating costs over four years. In all, the 2010 census is expected to cost more than $11 billion, nearly double the cost of the census done in 2000, according to congressional testimony.

The $600 million project budget covers the cost of developing and manufacturing the handhelds, plus the installation of secure wireless capabilities and related technology at 13 data centers and nearly 500 field offices, Murray said.

The Census Bureau spokesman declined to comment in detail about the handheld project. He also wouldn't address questions about potential funding issues, beyond referring back to congressional testimony last July in which Census Bureau Director Louis Kincannon said that recent legislative actions were forcing the agency "to question key operational and design considerations" for projects such as the handheld rollout.