> For the complete documentation index, see [llms.txt](https://docs.uidai.gov.in/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.uidai.gov.in/readme/verifiable-credential-specifications/iso-18013-5-aadhaar-mdoc-specs.md).

# 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
```

3. **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.