Prime Minister Narendra Modi is pushing Indians to link their digital IDs to a host of services such as credit cards and cellphones, even as the Supreme Court will decide on Friday the scope of the world's largest biometric database.

Almost 1 billion people had signed up for the program before a landmark privacy ruling in August strengthened the case against making the Aadhaar ID mandatory. The court will now decide on the validity of the government's order to meet specified deadlines. Last month, it told banks and utilities to stop scaring customers after people complained about a barrage of emails and text messages warning of frozen accounts and invalidated sim cards if they failed to comply with the government's push.

 To be sure, the court's immediate hearing will only pertain to the deadlines, with more detailed arguments on overall legality probably next year. While officials say Aadhaar is saving the government billions of dollars by better targeting beneficiaries of subsidized food and cash transfers, critics point to unfair exclusions and data leaks.