How to Fix PostSuisseID PKCS#11 Error When Signing PDFs on macOS
Question details
The user is unable to sign PDF documents using a PostSuisseID token due to a PKCS#11 error.
- Product
- Adobe Acrobat
- Device & OS
- macOS Catalina (and Mojave)
- Scenario
- Attempting to apply a digital signature to a PDF document using a PostSuisseID hardware token.
- Observed behavior
- Acrobat prompts for the password but then returns a PKCS#11 error code 0x91, generating the PDF without the required digital signature.
Ensure your macOS is fully updated and verify that you have administrative privileges to install or modify smart-card middleware and PDF software.
Update Acrobat and PostSuisseID Components
Updating to the latest compatible versions of the PDF reader, token middleware, and smart-card drivers resolves communication errors on newer macOS versions.
Major macOS updates, such as Catalina and Mojave, often introduce stricter security protocols that can break compatibility with older 32-bit drivers or outdated middleware. Ensuring all components are up to date is critical for the PKCS#11 module to function correctly.
Open Adobe Acrobat, navigate to the Help menu, and select 'Check for Updates'. Install any available updates and restart the application.
Visit the official PostSuisseID support portal to download and install the latest Catalina-compatible smart-card drivers and token middleware.
In Acrobat, go to Preferences > Signatures > Identities & Trusted Certificates. Click 'More', select 'PKCS#11 Modules and Tokens', and ensure the module path points to the newly installed middleware.
Use LocalSigner as a Temporary Workaround
If third-party PDF readers fail to communicate with the token, use a dedicated government signing tool to apply the digital signature.
Easily Sign and Secure Your PDFs with WPS Office
If you are experiencing persistent compatibility issues and middleware errors with other PDF software, switch to WPS Office. It offers a lightweight, highly compatible environment for securely handling and signing your PDF documents on macOS.
- 1. Open your PDF: Launch WPS Office and open the PDF document you need to sign.
- 2. Access the Signature Tool: Navigate to the 'Protect' or 'Fill & Sign' tab located in the top menu ribbon.
- 3. Create or Import Signature: Click on 'Sign' to either draw, type, or import an image of your signature.
- 4. Apply and Save: Place the signature securely on the document page, adjust its size, and save the finalized PDF.
Frequently Asked Questions
What does PKCS#11 error code 0x91 indicate?
Error code 0x91 typically indicates a communication failure or incompatibility between your PDF software, the operating system's security protocols, and the cryptographic token's middleware.
Why did my digital signature stop working after upgrading to macOS Catalina?
macOS Catalina dropped support for 32-bit applications and introduced stricter system security measures. If your smart-card drivers or token middleware were not updated to 64-bit compatible versions, they will fail to execute.
Where do I configure the PKCS#11 module in Adobe Acrobat?
You can configure this by navigating to Preferences > Signatures > Identities & Trusted Certificates > More. From there, select 'PKCS#11 Modules and Tokens' to attach the correct module file for your specific hardware token.
