> 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/remote-signing-document-signer/signing-modes-and-formats.md).

# Signing Modes and Formats

## Signing modes

| Mode                   | How it works                                                                                                                                         | When to use                                                               |
| ---------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------- |
| **Hash-based signing** | Client computes SHA-256 of the document (PDF byte range or data) and sends only the hash; service returns CMS/raw signature for the client to embed. | Documents must not leave your environment; highest throughput.            |
| **PDF signing**        | Client sends the PDF and appearance parameters; service returns the fully signed PDF.                                                                | Simplest integration; visible signatures and templates managed centrally. |
| **Bulk / batch**       | Up to 10 hashes per call; large jobs split by the client or SDK and processed in parallel.                                                           | Statements, certificates, payslips.                                       |

## Output formats

| Format                          | Description                                                     |
| ------------------------------- | --------------------------------------------------------------- |
| PAdES-B / PKCS#7 PDF            | Embedded signature in PDF, validates in Adobe Acrobat           |
| PAdES-LTV                       | Includes chain, OCSP/CRL and timestamp for long-term validation |
| CMS / PKCS#7 detached           | For non-PDF files or custom containers                          |
| XML signature (XMLDSig / XAdES) | For XML documents such as e-invoices and filings                |

## Visible signature options (PDF)

* Page number and coordinates, or a named signature field
* Signature image / organisation logo
* Reason, location and custom text
* Date/time format and timezone
* Lock document after signing (certification signature)

## Timestamping

All signatures can include an RFC 3161 timestamp from the eMudhra TSA, so they remain verifiable after the certificate expires.