- India launched Aadhaar in 2009 to streamline welfare payments
- Activists have raised concerns about privacy of Aadhaar data
- In August 2017, top court said privacy is a fundamental right
India launched Aadhaar, now the world's biggest biometric database, in 2009 to streamline welfare payments and reduce wastage in public spending.
Since then, the government of Prime Minister Narendra Modi has been keen to mandate the use of Aadhaar for everything from filing income tax to the registration of mobile phone numbers and booking railway tickets. Aadhaar is now mandatory for welfare, pension and employment schemes. In January, Aadhaar was made mandatory not only for the renewal of passport, but also for new passports issued within three days under the tatkaal category - an order that has been challenged by lawyer Vrinda Grover.
The top court's stand on Tuesday means that a deadline of March 31 that was earlier declared for bank accounts and mobile phones to be linked to Aadhaar, has now been extended till it decides on whether the Aadhaar Act is illegal.
Campaigners and technology experts have raised concern about the privacy and safety of data, the susceptibility of biometrics to failure, and the misuse of data for profiling or increased surveillance.
The government says the Supreme Court, in that verdict, accepted that privacy is a fundamental right, but subject to reasonable restrictions.
Critics are worried about repeated data breaches and say the ID card links enough data to create a full profile of a person's spending habits, their friends, property they own and a trove of other information.