How to Verify the Identity Behind a Digitally Signed PDF
Question details
The user wants to know how to confirm the true identity of a person who digitally signed a PDF, as anyone can manually input a name when creating a self-signed Digital ID.
- Product
- Device & OS
- not provided
- Scenario
- Receiving a digitally signed PDF and needing to ensure the signer's identity is genuine and cryptographically verified.
- Observed behavior
- The PDF displays a signature name, but it lacks clear proof of cryptographic verification or connection to a trusted Certificate Authority (CA).
Ensure you have a modern PDF reader installed that is capable of validating digital signatures, and maintain an active internet connection so the software can check the Certificate Revocation List (CRL) if needed.
Validate the Signature via Certificate Properties
Check the signature properties to verify that the certificate was issued by a recognized Certificate Authority (CA) rather than being a self-signed ID.
A name displayed on a signature provides no proof of identity, as anyone can create a self-signed profile with a fake name. True verification requires inspecting the underlying cryptographic certificate to ensure a trusted third party verified the signer.
Open the signed PDF in your PDF reader and click on the 'Signature Panel' icon, usually located on the left sidebar, or click directly on the signature field within the document.
Right-click the signature you want to verify and select 'Show Signature Properties' from the context menu to view its validation status.
Click 'Show Signer's Certificate' to inspect the certificate details. Look at the 'Issued By' field. A trusted signature will display a recognized Certificate Authority (such as DigiCert, GlobalSign, or an internal corporate CA) rather than the signer's own name.
Navigate to the 'Trust' tab to ensure the issuing certificate is added to your software's list of trusted identities.
Establish a Public-Key Infrastructure (PKI) Trust
For organizations, configure the PDF software to automatically trust certificates issued by an internal managed PKI or specific trusted third parties.
Securely Verify Digital Signatures with WPS Office
WPS Office provides a comprehensive PDF toolkit that allows you to easily verify digital signatures, inspect certificate details, and ensure the cryptographic authenticity of your important documents.
- 1. Open the PDF in WPS Office: Launch WPS Office and open your digitally signed PDF document.
- 2. Access the Protect Tab: Navigate to the 'Protect' tab on the top ribbon menu and click on 'Digital Signature', or simply click directly on the signature field in the document.
- 3. Validate Signatures: Click on 'Validate All Signatures' in the signature pane to instantly check the certificate status against trusted authorities.
- 4. View Certificate Details: Select the specific signature and click 'Certificate Details' to view the signer's identity and the issuing Certificate Authority.
Frequently Asked Questions
Why does a PDF signature display as 'Validity Unknown'?
This usually happens because the certificate used to sign the PDF is self-signed or its issuing Certificate Authority hasn't been added to your PDF reader's list of trusted identities. You must manually inspect the certificate and add it to your trusted list if you are certain of the sender's identity.
Can someone easily fake a digital signature on a PDF?
While anyone can type a fake name into a self-signed Digital ID, they cannot fake a cryptographic certificate issued by a recognized Certificate Authority (CA). Checking the certificate issuer in the signature properties is the only way to detect a forged identity.
What is a Certificate Authority (CA)?
A Certificate Authority is a highly secure, trusted third-party organization that rigorously verifies the identity of an individual or business before issuing them a digital certificate. This provides the necessary cryptographic trust for digital signatures.
