# File lib/rubygems/security.rb, line 463
    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