# File lib/openid/association.rb, line 111
    def make_pairs(message)
      signed = message.get_arg(OPENID_NS, 'signed')
      if signed.nil?
        raise ProtocolError, 'Missing signed list'
      end
      signed_fields = signed.split(',', -1)
      data = message.to_post_args
      signed_fields.map {|field| [field, data.fetch('openid.'+field,'')] }
    end