---
title: "Support for external signing services on Android | Nutrient"
canonical_url: "https://www.nutrient.io/guides/android/signatures/digital-signatures/signature-lifecycle/external-signing-service/"
md_url: "https://www.nutrient.io/guides/android/signatures/digital-signatures/signature-lifecycle/external-signing-service.md"
last_updated: "2026-06-09T10:25:14.352Z"
description: "Learn to integrate external signing services on Android using Nutrient. Sign documents with hardware security modules or other signing entities effectively."
---

# External signing services on Android

Nutrient supports external signature providers, such as hardware security modules (HSMs) and other signing entities. [`CustomSigning`](https://www.nutrient.io/api/android/nutrient/com.pspdfkit.signatures/-signing-manager/sign-document.html) from [`SigningManager.signDocument`](https://www.nutrient.io/api/android/nutrient/com.pspdfkit.signatures/-signing-manager/sign-document.html) provides a byte array to be signed by any external signing service.

The simplest way to sign a document is to provide [`KeyStore.PrivateKeyEntry`](https://developer.android.com/reference/kotlin/java/security/KeyStore.PrivateKeyEntry.html) in [`SigningOptions`](https://www.nutrient.io/api/android/nutrient/com.pspdfkit.signatures/-signer-options/index.html), and [`SigningManager`](https://www.nutrient.io/api/android/nutrient/com.pspdfkit.signatures/-signing-manager/index.html) will sign it. However, if a user needs to sign with an external service, then instead of a private key entry, the user can provide a list of `X509Certificate`s and then sign the document using the `CustomSigning` suspended function.

For an interactive example of external signing services on Android, check out [`ManualSigningExample`](https://github.com/PSPDFKit/pspdfkit-android-catalog/blob/9eac1be5767cdeb5a58d879d0749c2338d4f77fb/app/src/main/java/com/pspdfkit/catalog/examples/kotlin/ManualSigningExample.kt) in the Catalog app.
---

## Related pages

- [How to add signature fields to PDFs on Android](/guides/android/signatures/digital-signatures/signature-lifecycle/add-a-signature-field.md)
- [Biometric signatures on Android](/guides/android/signatures/digital-signatures/signature-lifecycle/biometric.md)
- [Master digital signatures in Android efficiently](/guides/android/signatures/digital-signatures/signature-lifecycle/overview.md)
- [How to create and validate digital signatures on Android](/guides/android/signatures/digital-signatures/signature-lifecycle/prepare-the-certificates-for-signing.md)
- [Sign a PDF with a certificate on Android](/guides/android/features/digital-signatures.md)
- [Configure digital signature appearance in Android: Visible vs. non-visible signatures](/guides/android/signatures/digital-signatures/signature-lifecycle/signature-appearance.md)
- [Securely validate digital signatures in Android apps](/guides/android/signatures/digital-signatures/signature-lifecycle/validation.md)