> For the complete documentation index, see [llms.txt](https://docs.emudhradigital.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.emudhradigital.com/documentation/esign-v2-online-aadhaar-ekyc/esign-v2-overview.md).

# eSign v2 Overview

**eSign v2** is eMudhra's implementation of the CCA *eSign API Specification 2.1 — Online Aadhaar & Others*. The signer is authenticated in real time against UIDAI, a one-time key pair and eKYC class DSC are generated for that transaction, the document hash is signed and the private key is destroyed.

No registration or enrolment is required — any Aadhaar holder can sign.

## At a glance

| Attribute             | Value                                                                    |
| --------------------- | ------------------------------------------------------------------------ |
| Specification         | eSign API 2.1 (supersedes 2.0; ESP readiness 07.04.2023)                 |
| Identity source       | Online Aadhaar eKYC (UIDAI)                                              |
| Authentication modes  | OTP / TOTP, fingerprint, iris, face                                      |
| Certificate           | eKYC class, one-time use, valid ≤ 30 minutes                             |
| Documents per request | 1                                                                        |
| Hash algorithm        | SHA-256 (hex)                                                            |
| Signature types       | `rawrsa`, `rawecdsa`, `PKCS7`, `PKCS7pdf`, `PKCS7complete`               |
| Interaction           | Synchronous — browser/app redirect with response POSTed to `responseUrl` |

## Authentication variants supported by eMudhra

| Variant                 | AuthMode | Assurance class                | Where it works                                                                                                                                                                                                     |
| ----------------------- | -------- | ------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| **Aadhaar OTP / T-OTP** | `1`      | Single factor                  | Web, Android and iOS; OTP sent to Aadhaar-linked mobile                                                                                                                                                            |
| **Aadhaar Fingerprint** | `2`      | Multi factor                   | Desktop web or Android with a UIDAI-certified L1 RD device (not iOS)Desktop web or Android with a certified RD iris scanner (not iOS)Face authenticationAndroid and iOS (intent, App-to-App, SDK); not desktop web |
| **Aadhaar Iris**        | `3`      | Multi factor                   | Desktop or Android with a certified RD iris scanner                                                                                                                                                                |
| **Aadhaar Face**        | `4`      | Face authentication (see note) | Android with UIDAI AadhaarFaceRD app; no external device                                                                                                                                                           |

See [Authentication Modes](broken://pages/4128f625f2b4cd26edd59929bda7cc12d1a9ddbe) for detail.

## Integration models supported by eMudhra

| Model                      | Summary                                                                                                                                                |
| -------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------ |
| **Web (browser redirect)** | ASP web page posts the signed XML to the eMudhra eSign gateway; user authenticates on eMudhra pages; response is posted back.                          |
| **Web-to-App**             | User starts on the web; biometric or face capture is handed off to a device app (RD service or eMudhra app), then the flow returns to the web session. |
| **App-to-App**             | ASP's native app invokes the eMudhra eSign app / gateway through an intent or universal link and receives the response back.                           |
| **Embedded SDK**           | eMudhra Android/iOS SDK integrated inside the ASP's app, providing the eSign UI, RD-service orchestration and response handling in-app.                |
| **emSigner gateway**       | Use eSign through emSigner without becoming an ASP.                                                                                                    |

See [Integration Models](broken://pages/d5d4da7935e182f7d3b3295bf70480038f3b9a2f) for detail.

## When to choose eSign v2

* Retail, consumer-scale signing where users already have Aadhaar.
* Assisted channels (branches, agents, BCs) using fingerprint or face authentication.
* One document per signing event (for multiple documents, consider [eSign v3](file:///0255771/eSign-v3/eSign%20v3%20Overview.md) or [Remote Key Storage](file:///0255771/Remote-Key-Storage/Remote%20Key%20Storage%20Overview.md)).