Patent ID: 7634654

Claim:
A method for nullifying, by a communications apparatus, a public-key certificate for use by a communications counterpart of the communications apparatus in an authentication process, comprising: transferring to the communications counterpart, by said communications apparatus, a nullifying public-key certificate configured to nullify the public-key certificate, when determining, based on the public-key certificate being a valid public-key certificate received from said communications counterpart or information received via a communications path based on the public-key certificate, that said public-key certificate is to be nullified; and setting, by the communications counterpart, the nullifying public-key certificate as the public-key certificate, wherein said nullifying public-key certificate has a format that is valid as the public-key certificate and includes content to nullify the nullifying public-key certificate itself; and said nullifying public-key certificate is configured to pass a format check for confirming a format of the nullifying public-key certificate and a content check for confirming integrity of the content of the nullifying public-key certificate, while including the content to nullify the nullifying public-key certificate itself.