ISO 18013-5 Aadhaar mDoc Specs

This document covers mDoc schema specifications

1. Introduction

This specification defines the Aadhaar mDoc schema for digital identity verification compliant with ISO/IEC 18013-5. It enables:

• Privacy-preserving identity sharing

• Offline-capable verification

• Selective disclosure of Aadhaar attributes

• Cryptographic integrity using COSE and salted hashes

2. mDoc Data Model

2.1 Encoding Format

Item	Specification
Data Format	CBOR
Object Signing	COSE_Sign1 (RFC 9052)
Namespace Model	Modular namespace-based
Digest Algorithm	SHA-256
Claim Protection	Salted Hash per attribute

Each claim is encoded as:

IssuerSignedItem = {
  digestID: uint,
  random: bstr,              ; per-claim salt
  elementIdentifier: tstr,   ; claim name
  elementValue: any          ; claim value
}

2.2 Namespace Definition

Namespace: in.gov.uidai.aadhaar.1

All resident attributes reside inside this UIDAI namespace. Each element is wrapped in CBOR Tag 24 for cryptographic isolation.

2.3 Issuer Authentication (issuerAuth)

The issuerAuth field is a COSE_Sign1 structure containing the Mobile Security Object (MSO).

Component	Description
Protected Header	Signing algorithm metadata (e.g., ECDSA-256)
Unprotected Header	X.509 certificate or UIDAI key reference
Payload	Mobile Security Object (MSO)
Signature	UIDAI signature over protected headers + MSO

2.4 Mobile Security Object (MSO)

The MSO links issuer signature → salted claim hashes.

Field	Description
digestAlgorithm	Hash algorithm (SHA-256)
valueDigests	Map of namespace → digestID → hash
deviceKey	Holder device public key
docType	in.gov.uidai.aadhaar.1
validityInfo	signed / validFrom / validUntil timestamps

The MSO prevents signing each attribute individually and enables selective disclosure verification.

2.5 Credential Validity Rules

Credential validity = earliest of:

1. Default Expiry: 1 year from issuance

2. Aadhaar Expiry: aadhaar_expires_on

3. Status Update: Age/eligibility state change

2.6 Supported Claims

All listed claims are selectively disclosable (Y) — meaning the holder can share them individually.

Field	Description / Meaning	Selectively Disclosable
CredentialIssuingDate	Credential Issuance Date	Y
EnrolmentDate	Enrolment Date	Y
EnrolmentNumber	Enrolment Number	Y
IsNRI	Whether the Resident is an NRI or not	Y
IsResidentForeigner	Whether the resident is a foreign national	Y
AadhaarType	Type of Aadhaar (RF / NRI / IN)	Y
AadhaarExpiresOn	Date of Expiry for the Aadhaar	Y
MaskedUID	Masked UID of Resident	Y
ResidentName	Name of the Aadhaar Holder	Y
LocalResidentName	Local language name of the Aadhaar Holder	Y
Dob	Date of Birth	Y
Email	Email ID of resident	Y
MaskedEmail	Masked Email	Y
Mobile	Mobile number	Y
MaskedMobile	Masked mobile number	Y
Gender	Gender of the Aadhaar Holder	Y
ResidentImage	Photo of the Aadhaar holder	Y
AgeAbove18	Is age above 18 years?	Y
AgeAbove50	Is age above 50 years?	Y
AgeAbove60	Is age above 60 years?	Y
AgeAbove75	Is age above 75 years?	Y
CareOf	Guardian / Head of Family name	Y
LocalCareOf	Guardian / HOF name in local language	Y
Building	Building details	Y
LocalBuilding	Building details in local language	Y
Locality	Locality details	Y
LocalLocality	Locality in local language	Y
Street	Street details	Y
LocalStreet	Street in local language	Y
Landmark	Landmark details	Y
LocalLandmark	Landmark in local language	Y
Vtc	Village / Town / City	Y
LocalVtc	Village / Town / City in local language	Y
SubDistrict	Sub-district details	Y
LocalSubDistrict	Sub-district in local language	Y
District	District details	Y
LocalDistrict	District in local language	Y
State	State details	Y
LocalState	State in local language	Y
PoName	Post Office Name	Y
LocalPoName	Post Office name in local language	Y
PinCode	Pin code	Y
Address	Full address (individual fields also disclosable)	Y
RegionalAddress	Address in local language	Y

2.7 Verification Workflow

1. Signature Verification Validate COSE signature using UIDAI public key.

2. Hash Verification For each disclosed claim:

hash(random || CBOR(elementValue)) == MSO valueDigest

1. Device Binding Ensure MSO deviceKey matches presenting device key.

2.7 Security Architecture

Mechanism	Purpose
CBOR	Compact binary transport
COSE	Tamper-proof signing
Salted Hashes	Prevent dictionary attacks
Device Key Binding	Prevent cloning
Namespace Isolation	Modular claim separation

3.0 Standards & Technology Implementation

3.1 Object Representation (CBOR)

Concise Binary Object Representation (CBOR) is the primary encoding format. It is designed for interoperability with JSON but offers a more compact binary footprint. This allows for faster offline transmission (via NFC or BLE) and supports complex data types like images with reduced size overhead.

6.2 Object Signing (COSE)

To ensure data is tamper-proof, UIDAI uses CBOR Object Signing and Encryption (COSE) . Every mso is signed as a COSE_Sign1 message. This process authenticates both the Issuer (UIDAI) and binds the document to the Holder's Device Key , preventing unauthorized cloning of the credential.

6.3 Hashed Salted Claims

Aadhaar mDocs use salted hashes to enhance privacy. Each claim is combined with a unique "salt" (the random hex value) before being hashed. This prevents "dictionary attacks" where a verifier could guess a birthdate by comparing hashes, ensuring that shared data remains private and unique to each transaction.