Aadhaar

What is Aadhaar?

Aadhaar is India’s national digital identity system maintained by UIDAI (Unique Identification Authority of India).

• It is a 12-digit unique identity number issued to residents of India, based on their biometric and demographic data.

• Aadhaar serves as a foundational ID that can be used to verify identity across financial, telecom, and government services.

• Verification is done via UIDAI APIs or Aadhaar-linked services, such as QR codes.

UIDAI does not sign the entire Aadhaar number and only the last 4 digits. As this does not have enough entropy to create a nullifer we also use other fields such as the name, date of birth, and gender. This also means that person can change their Aadhaar and be considered as a "new" person in the protocol. Although we have chosen fields that are hard to change edge cases do pop up such as people changing their names due to marriage, divorce or other legal corrections.

Registering with Aadhaar on Self

Self allows users to prove identity using Aadhaar in a privacy-preserving way. There are two common methods:

1. Using the mAadhaar app

   1. Download the official mAadhaar app from UIDAI (Android/IOS).

   2. Inside the app, generate a QR code that contains Aadhaar demographic details.

      

      mAadhaar
   3. Upload this QR code in the Self app to register.

      1. Self processes this QR to derive a unique nullifier (an identifier) that allows users to prove uniqueness without sharing their Aadhaar number directly.

2. By using the UIDAI website

   1. Go to the UIDAI website

   2. Enter your Aadhaar number, and verify yourself with an OTP to get a PDF.

   3. Take a screenshot of the QR code in the pdf and upload in the Self app.

The password to the PDF in both cases is the first four letters of your name in caps following by your birth year.

Working with attributes in Aadhaar

Since Aadhaar uses a different format than passports, keep in mind that some of the disclosed attribute formats can be different.

GenericDiscloseOutputV2

Field	Type	Formatting / Value
forbiddenCountriesListPacked	uint256[4]	Packed bytes of all countries into an array 4 uint256 numbers.
issuingState	string	Varies**
name	string[]	First value contains the entire name (and it may vary)
idNumber	string	Last 4 letters of the aadhaar number.
nationality	string	'IND'
dateOfBirth	string	DD-MM-YYYY
gender	string	'M' | 'T' | 'F'
expiryDate	string	'UNAVAILBLE'
olderThan	uint256	0 - 99
ofac	bool[3]	Each value is true if ofac check is enabled.

GenericDiscloseOutput

Field	Type	Formatting / Value
forbiddenCountriesListPacked	string[]	Packed bytes list of forbidden countries
issuingState	string	Varies
name	string	Full name. Can vary as well
idNumber	string	Last 4 digits of aadhaar
nationality	string	'IND'
dateOfBirth	string	YYYYMMDD
gender	string	'M' | 'T' | 'F'
expiryDate	string	'UNAVAILABLE'
minimumAge	string	'00'-'99'
ofac	bool[]	True if in ofac

**Varies refers to a string being all caps / lowercase / first letter in caps and the rest in lowercase.