# File lib/openid/filestore.rb, line 206
    def use_nonce(nonce)
      filename = @nonce_dir.join(nonce)
      begin
        st = File.stat(filename)
      rescue Errno::ENOENT
        return false
      else
        begin
          File.unlink(filename)
        rescue Errno::ENOENT
          return false
        end      
        nonce_age = Time.now.to_f - st.mtime.to_f
        nonce_age <= @max_nonce_age
      end
    end