Aadhaar: Technology and Architecture [pdf]

Aadhaar is India's national unique identity program, and has collected biometric and other personal data of over 1 billion people. These people have done an impressive work of deduplicating so many identities based on both fingerprint and iris scan data.

There is controversy around Aadhaar at the moment, the Supreme court had ruled that Aadhaar cannot be made mandatory for people, and the government is trying to get around it using new legislation. There had been no legislation around Aadhaar till now, and there are objections that it had been falsely claimed/advertised as mandatory while trying to enroll people.

There is no privacy legislation in India right now, and it isn't clear if privacy is a fundamental right, so this makes Aadhaar particularly problematic, as it is not clear with whom the data can be shared.

The Aadhaar people, to their credit, have generally cared about privacy, and have refused to divulge data on several requests. Whether they are technically capable of securing the data remains to be seen. This pdf goes into some detail of their high-level architecture. You can compare and contrast this with other national id systems, such as Estonia's smart card id systems.