A service providing system that, when providing a service to any one of a plurality of communication terminals, causes an authentication system to perform authentication of a user of the any one communication terminal, the service providing system comprising: a receiving part to receive, from the any one communication terminal, a password and terminal identification information to identify the any one communication terminal, the terminal identification information including a to-be-authenticated section to be used for the authentication of the user and a not-to-be-authenticated section not to be used for the authentication of the user, wherein the not-to-be-authenticated section includes information to identify the any one communication terminal; and a transmitting part to transmit, to the authentication system, the password and only the to-be-authenticated section out of the received terminal identification information; wherein the receiving part receives from the authentication system an authentication result of the authentication, and the service providing system further comprises a session management part to, in a case where the authentication result is affirmative, associate with the terminal identification information received by the receiving part session identification information to identify a communication session to be established with the any one communication terminal for providing the service to the communication terminal and to manage the session identification information and the terminal identification information; whereby the authentication system can transmit the authentication result to the service providing system upon validation by the authentication system of the password and the to-be-authenticated section out of the received terminal identification information; and in establishing the session for providing the service to any of the plurality of communication terminals, the password and the to-be-authenticated section out of the received terminal identification information is the same for the plurality of communication terminals. a receiving part to receive, from the any one communication terminal, a password and terminal identification information to identify the any one communication terminal, the terminal identification information including a to-be-authenticated section to be used for the authentication of the user and a not-to-be-authenticated section not to be used for the authentication of the user, wherein the not-to-be-authenticated section includes information to identify the any one communication terminal; and a transmitting part to transmit, to the authentication system, the password and only the to-be-authenticated section out of the received terminal identification information; wherein the receiving part receives from the authentication system an authentication result of the authentication, and the service providing system further comprises a session management part to, in a case where the authentication result is affirmative, associate with the terminal identification information received by the receiving part session identification information to identify a communication session to be established with the any one communication terminal for providing the service to the communication terminal and to manage the session identification information and the terminal identification information; whereby the authentication system can transmit the authentication result to the service providing system upon validation by the authentication system of the password and the to-be-authenticated section out of the received terminal identification information; and in establishing the session for providing the service to any of the plurality of communication terminals, the password and the to-be-authenticated section out of the received terminal identification information is the same for the plurality of communication terminals.