    # File lib/rubygems/security.rb, line 727
      def self.add_trusted_cert(cert, opt = {})
        opt = OPT.merge(opt)

        # get destination path
        path = Gem::Security::Policy.trusted_cert_path(cert, opt)

        # verify trust directory (can't write to nowhere, you know)
        verify_trust_dir(opt[:trust_dir], opt[:perms][:trust_dir])

        # write cert to output file
        File.open(path, 'wb') do |file|
          file.chmod(opt[:perms][:trusted_cert])
          file.write(cert.to_pem)
        end

        # return nil
        nil
      end