Provided is a system and method for authentication. The method includes receiving a subscription request from a user terminal, the subscription request executed by an authentication server communicating with the user terminal and including group discrimination data including a group code and information for discriminating a group from another, if it is determined that the group code and the information included in the group discrimination data correspond to each other, performing a group authentication procedure on the user terminal and processing the group authentication procedure as being successful, issuing a member session key to the user terminal, and providing a service requested by the user terminal in response to the service request including the member session key from the user terminal. In one embodiment, it is possible to prevent information on service users from being divulged.