When you validate or view properties of a digital signature or an embedded timestamp, the validity status may display “unknown” or “could not be verified”. You need to add the certificate that issued your digital IDs as well as the time stamp server to the Trusted Certificates list.
To add a trusted digital certificate to the Trust Certificates list, please do the following:
- Right-click the digital signature, and choose Show Signature Properties.
- In the Signature Properties dialog box, click Show Certificate.
- In the Certificate Viewer dialog box, specify the trust level for the certificate in the Trust tab:
- Use this certificate as a trusted root: Use the certificate as a trusted root, and trust all certificates issued by that certificate authority. Once you make a certificate a trust anchor, revocation checking will not be performed on it.
- Validating Signatures or Validating Certified Documents: Trust the certificate when validating signatures or certified documents.
- Click Add to Trusted Certificates, and confirm your operation.
To add a trusted time stamp server to the Trusted Certificates list, please do either of the following:
- If a time stamp is added in the document, go to the Digital Signatures panel in the navigation pane, right-click the timestamp signature, and choose Show Signature Properties. In the pop-up Signature Properties dialog box, click Show Certificate. See also Add a trusted digital certificate to the Trust Certificates list.
- If a time stamp is added to a digital signature, right-click the signature field in the document or right-click the signature in the Digital Signatures panel, and choose Show Signature Properties from the context menu. Click Advanced Properties in the lower-left corner of the pop-up Signature Properties dialog box, which opens the Advanced Signature Properties dialog box. Then click Show Certificate. See also Add a trusted digital certificate to the Trust Certificates list.
To check all the trusted certificates, choose Protect > Sign & Certify > Trusted Certificates. In the Trust Certificates window, you can manage all the trusted certificates, including adding & exporting a certificate, viewing certificate details, deleting a certificate, and specifying the trust level for a certificate.