An authentication server that authenticates a user of a user terminal that executes streaming of content provided by a content server, the authentication server authenticating the user for the streaming, and the authentication server comprising: storage means that stores registration information of a plurality of users; authentication means that, when the authentication means receives an authentication request for streaming of content designated by a first user among the plurality of users from a user terminal that the first user is using, compares information included in the authentication request with the registration information and authenticates the first user; generation means that, if the authentication succeeds, generates a first token indicating that the first user is an authenticated user; and communications means that transmits the generated first token to the user terminal, wherein, the communications means is configured to receive a token reissue request from the user terminal, the token reissue request being sent in response to a determination that a predetermined duration has passed from the start of playback of the content, and transmit, in response to receiving the token reissue request, an enquiry to the content server as to whether the streaming of the designated content from the content server to the user terminal is continuing, if the communications means receives a response from the content server that the streaming of the designated content from the content server to the user terminal is continuing, the generation means is further configured to generate a second token relating to the same content as the content designated by the first user, and the communications means is further configured to transmit the second token to the user terminal, wherein each of the first and second tokens is for a predetermined number of uses. storage means that stores registration information of a plurality of users; authentication means that, when the authentication means receives an authentication request for streaming of content designated by a first user among the plurality of users from a user terminal that the first user is using, compares information included in the authentication request with the registration information and authenticates the first user; generation means that, if the authentication succeeds, generates a first token indicating that the first user is an authenticated user; and communications means that transmits the generated first token to the user terminal, wherein, the communications means is configured to receive a token reissue request from the user terminal, the token reissue request being sent in response to a determination that a predetermined duration has passed from the start of playback of the content, and transmit, in response to receiving the token reissue request, an enquiry to the content server as to whether the streaming of the designated content from the content server to the user terminal is continuing, if the communications means receives a response from the content server that the streaming of the designated content from the content server to the user terminal is continuing, the generation means is further configured to generate a second token relating to the same content as the content designated by the first user, and the communications means is further configured to transmit the second token to the user terminal, wherein each of the first and second tokens is for a predetermined number of uses.