    # File lib/rubygems/security.rb, line 401
        def self.trusted_cert_path(cert, opt = {})
          opt = Gem::Security::OPT.merge(opt)

          # get digest algorithm, calculate checksum of root.subject
          algo = opt[:dgst_algo]
          dgst = algo.hexdigest(cert.subject.to_s)

          # build path to trusted cert file
          name = "cert-#{dgst}.pem"

          # join and return path components
          File::join(opt[:trust_dir], name)
        end