This dialog box serves to store the Public Key ID files of people who trust you and you want to trust. Call it from Security > IDs and Certificates > Trusted Identities using this tool:
Click Browse to locate and add a Public Key ID file someone has sent you. Typically this will be a file with an extension p7b, p7c or cer. To see the typical contents of such a file go to Digital Identities Overview. You should also add the certificates of Time Stamp Authorities if you want to use their services to verify the authenticity of dates and times in signatures. You should add the certificate from any Certificate Authority (CA) you or your partners want to use.
Click Search to help you locate such files on Directory Servers maintained by Certificate Authorities.
Click Details to see all available information inside the selected ID file.
Click Export to send the selected file to a location in your system for re-use.
Click Delete to remove the selected trusted ID file.
Select a Trusted ID file from a Certificate Authority and click Set as a Trusted Root to always trust any document sent via this Authority.