A digital certificate is provided to a customer having an electronic
account linked to the customer's physical address. Using the digital
certificate, the customer performs electronic transactions with a third
party. A proofing workstation receives a request from a third party to
validate the digital certificate. The proofing workstation communicates
with a proofing server that maintains a list of valid certificates and a
list of revoked certificates. The proofing server sends a response to the
proofing workstation, where it is received by the third party.