India's biometric database notched up one billion members on Monday, as the government sought to allay concerns about privacy breaches in the world's biggest such scheme.
The database was set up seven years ago to streamline benefit payments to millions of poor people as well as to cut fraud and wastage.
Under the scheme, called Aadhaar, almost 93 percent of India's adult population have now registered their fingerprints and iris signatures and been given a biometric ID, according to the government.
IT minister Ravi Shankar Prasad hailed it as "an instrument of good governance" at a ceremony in New Delhi marking the crossing of the one-billion member mark.
Prasad said the initiative, inherited from the previous left-leaning Congress government, had enabled millions to receive cash benefits directly rather than dealing with middlemen.
He said the government had saved 150 billion rupees ($2.27 billion) on its gas subsidy scheme alone -- by paying cash directly to biometric card holders instead of providing cylinders at subsidised rates.
He also said all adequate safeguards were in place to ensure the personal details of card holders could not be stolen or misused by authorities given access to the database.
"We have taken all measures to ensure privacy. The data will not be shared with anyone except in cases of national security," Prasad said.
His comments come after parliament passed legislation last month giving government agencies access to the database in the interests of national security.
It was passed using a loophole to circumvent the opposition in parliament, where the ruling Bharatiya Janata Party (BJP) lacks a majority in the upper house.
The way it was passed, as well as the legislation itself, raised concerns about government agencies accessing private citizens' details.
Internet experts have also raised fears about the safety of such a massive database, including hacking and theft of details.
"It was as if Indian lawmakers wrote an open letter to criminals and foreign states saying, 'we are going to collect data to non-consensually identify all Indians and we are going to store it in a central repository. Come and get it!'," Sunil Abraham, executive director of the Centre for Internet and Society, wrote in India's Frontline news magazine.