Electronic authentication with a portable device such as a smart card has been receiving increasing attention. An explosion of papers argues security on such kind of authentication, however the human concerned in an authentication is often regarded as his/her portable device. This paper considers an identification of a server computer of a service provider by a human with a portable device as a part of the authentication and an attack by a client computer which relays the communication between the portable device and the server computer. As a defense against the attack, we introduce a system with a portable device which has an interface to show information to a human.