> 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/api-reference/remote-key-storage-api/remote-key-storage-api-overview.md).

# Remote Key Storage API Overview

Implements **CCA eSign Remote API 1.1**. Subscribers enrol a long-term key held in an eMudhra HSM and sign with an AuthPIN verified inside the HSM.

{% hint style="info" %}
**Interactive reference (Swagger / OpenAPI):** [Remote Key Storage API — Swagger](https://todo-swagger-url/remote-key-storage)

*Placeholder link — to be replaced with the published Swagger URL.*
{% endhint %}

## Operations

| # | Operation             | Transport                    | Payload                         |
| - | --------------------- | ---------------------------- | ------------------------------- |
| 1 | Certificate enrolment | Browser form POST            | `txnreq` / `txnresp`            |
| 2 | Initiate signing      | HTTPS POST `application/xml` | Signed `<Esign>` → `status="2"` |
| 3 | Signer authentication | Browser form POST            | `txnref` = Base64(\`txn         |
| 4 | Final response        | HTTPS POST to `responseUrl`  | Signed `<EsignResp>`            |
| 5 | Status check          | HTTPS POST `application/xml` | Signed `<EsignStatus>`          |

## Key limits

| Item                        | Value                                                     |
| --------------------------- | --------------------------------------------------------- |
| Documents per authorisation | Up to 10                                                  |
| Default key / validity      | ECC P-256 with SHA-256 · 2 years                          |
| AuthPIN lockout             | 10 wrong attempts → locked ≥ 1 hour; 3 cycles → permanent |
| Session token               | Single-use, bound to `txn` and exact hashes               |