---
title: "iOS PDF digital signature solutions"
canonical_url: "https://www.nutrient.io/guides/ios/signatures/digital-signatures/supported-methods/"
md_url: "https://www.nutrient.io/guides/ios/signatures/digital-signatures/supported-methods.md"
last_updated: "2026-06-03T21:45:02.511Z"
description: "Explore secure signing methods for iOS PDFs with advanced electronic signatures and encryption options to keep your documents safe."
---

# Secure digital signatures for iOS PDF libraries

Nutrient supports the following signing methods:

- `PAdES` (PDF Advanced Electronic Signatures, ETSI.CAdES.detached)

- `CMS` (adbe.pkcs7.detached)

Supported signing algorithms are:

- `RSA`

- `ECDSA`

Supported hashing algorithms include:

- `MD4`

- `MD5`

- `SHA-2 (SHA-224, SHA-256, SHA-384, SHA-512, SHA-512-256)`

A hashing algorithm is an algorithm that converts a large amount of data (your PDF document) to a fixed-length string. If someone changes one bit of data in your PDF document, the hashing algorithm produces a different string, so if you store that hash inside the PDF document, you could potentially know when it has been changed by a third party. However, as easy as it sounds, this approach is insecure. If someone knows the hashing algorithm that was used to sign the PDF, they could replace the hash inside the PDF so that it validates as authentic. To avoid this, Nutrient works with encryption algorithms.

More specifically, Nutrient supports `RSA`, one of the most popular public key encryption algorithms. `ECDSA`, an algorithm based on elliptic curve cryptography, is also supported. Cryptographic systems based on `ECDSA` are becoming the de facto standard for messaging and systems security. For example, in the [Apple Platform Security](https://www.apple.com/business/docs/iOS_Security_Guide.pdf) guide, Apple explains how it uses `ECDSA` extensively in its mobile operating system, along with detailing its benefits when compared to other algorithms.
---

## Related pages

- [Adding a Digital Signature to a PDF on iOS](/guides/ios/features/digital-signatures.md)
- [Biometric Signatures on iOS](/guides/ios/signatures/digital-signatures/biometric.md)
- [Contained Digital Signatures on iOS](/guides/ios/signatures/digital-signatures/contained-signatures.md)
- [Signatures in iOS Viewer](/guides/ios/signatures/digital-signatures/built-in-ui.md)
- [Sign PDFs and Add Custom Encryption on iOS](/guides/ios/signatures/digital-signatures/custom-signers.md)
- [Troubleshooting](/guides/ios/signatures/digital-signatures/troubleshooting.md)
- [Customizing Digital Signatures on iOS](/guides/ios/signatures/digital-signatures/customization.md)
- [Generate a Self-Signed Certificate for Signing on iOS](/guides/ios/signatures/digital-signatures/generate-certificate.md)
- [Digital Signature Standards: CAdES and PAdES](/guides/ios/signatures/digital-signatures/standards.md)
- [Validating a Digital Signature on iOS](/guides/ios/signatures/digital-signatures/validation.md)