Aadhaar SD-JWT Specifications

This page defines the specifications of Aadhaar SD-JWT

1. Introduction

This document defines the Aadhaar Verifiable Credential (VC) format in accordance with the Selective Disclosure JSON Web Token (SD-JWT) standard (RFC 9901). The credential allows Aadhaar Number Holders (ANHs) to present Aadhaar demographic attributes in a privacy-preserving, cryptographically verifiable, and selectively disclosable format.

The specification is aligned with:

• IETF SD-JWT (RFC 9901)

• W3C Verifiable Credentials (v1)

• OpenID4VP for verifiable presentation

This document covers only the SD-JWT credential structure.

2. High-Level Structure

An SD-JWT Credential is delivered as:

<issuer-signed-sd-jwt> ~ <disclosures...>

Where:

• The issuer-signed component contains digests of claims.

• The disclosures contain claim plaintexts that the holder chooses to reveal.

3. Protected Header Requirements

The SD-JWT protected header contains:

{
  "alg": "ES256",
  "typ": "vc+sd-jwt",
  "kid": "abcd12354"
}

Whereas

• alg

  • ES256.

• typ

  • vc+sd-jwt as per SD-JWT standard.

• kid

  • References the UIDAI issuer signing key stored in the JWKS endpoint.

4. Issuer-Signed Payload (SD-JWT)

The payload includes:

4.1 Mandatory Fields

Field	Type	Description
iss	string	https://uidai.gov.in
id	string	Unique credential identifier (UUID v4)
iat	number	UNIX timestamp of issuance
exp	number	UNIX timestamp of expiry
status	string	URL to status endpoint
_sd_alg	string	SHA-256
_sd	array	Salted claim digests
cnf	object	Holder-binding JWK

4.2 Holder Binding (cnf.jwk)

The credential binds to a public key controlled by the holder (aadhaar app).

Supported key types:

• EC P-256

"cnf": {
  "jwk": {
    "kty": "EC",
    "crv": "P-256",
    "x": "<base64url>",
    "y": "<base64url>",
    "kid": "<holder-key-id>",
    "alg": "ES256"
  }
}

5. Claim Encoding and Selective Disclosure

Aadhaar demographic attributes are encoded using salted-hash digests.

5.1 Claim Process

For every claim:

digest = SHA-256( base64url(salt) || base64url(name) || base64url(value) )

The digest is included in _sd.

The corresponding disclosure is:

[name, value, salt]

Example digest list:

"_sd": [
  "Pwb8CAFTk6KYrhJDNzdW37MFZJ-sxaHAf0Q7AGZrwXg",
  "wuj7vq4gOtFPsuhYivf6mHi1O9xcmKhs-TOHDTGlaAM",
  ...
]

6. Aadhaar Claim Set

Claim	Type	Notes
uid	string	Optional — typically NOT disclosed
name	string	Selectively disclosed
dob	string	YYYY-MM-DD or age-derived boolean
gender	string	“M”, “F”, “T”
address	object	Structured, selectively disclosable fields
mobile	boolean	Whether UIDAI has verified mobile
email	boolean	Same for email
age_over_18	boolean	Derived claim
age_over_60	boolean	Derived claim

8. Credential Status

The status field contains a stable URL that returns signed VC status metadata.

https://pehchaan.uidai.gov.in/credentials/status/<credential-id>

Status values:

• active

• suspended

• revoked

Status response is digitally signed.

9. Example SD-JWT Payload (Normalized)

{
  "iss": "https://uidai.gov.in",
  "id": "02bf1830-46e4-4564-b5ca-734280901673",
  "iat": 1711805307,
  "exp": 1711895307,
  "status": "https://pehchaan.uidai.gov.in/credentials/status/02bf1830-46e4-4564-b5ca-734280901673",

  "cnf": {
    "jwk": {
      "kty": "EC",
      "crv": "P-256",
      "x": "<base64url-x>",
      "y": "<base64url-y>",
      "kid": "<holder-key-id>",
      "alg": "ES256"
    }
  },

  "_sd_alg": "SHA-256",
  "_sd": [
    "Pwb8CAFTk6KYrhJDNzdW37MFZJ-sxaHAf0Q7AGZrwXg",
    "wuj7vq4gOtFPsuhYivf6mHi1O9xcmKhs-TOHDTGlaAM",
    ...
  ]
}