An embodiment of the present invention provides a method for performing authentication on a subscriber terminal in a digital television (DTV) network which comprises at least one subscriber terminal and a head end for sending encrypted DTV program data to each subscriber terminal, the subscriber terminal comprising a set top box (STB) and a subscriber identification module for storing key information for decrypting the DTV program data, the method including: reading, by the STB, the life cycle of the key from the subscriber identification module when the STB starts up; initiating, by the STB, an authentication request to the head end when the life cycle expires; performing, by the head end, authentication after receiving the authentication request, and sending a response message to the STB; receiving, by the STB, the response message, and updating the key information when the response message is a response message which indicates successful authentication.