Apparatus and method of authentication for non-realtime iptv system

PURPOSE: An authentication apparatus for a non-real-time IP(Internet Protocol) television system and method thereof are provided to maintain safety for service denial attacks using the variation of a time stamp. CONSTITUTION: When an authentication result for a content request message is effective, an authentication apparatus encrypts the variation of a time stamp between the authentication apparatus and an apparatus using a session key(S405,S407). The authentication apparatus creates authentication information which the apparatus authenticates the authentication apparatus using a second encryption value(S411). The authentication apparatus transmits the authentication information with content corresponding to the content request message to the apparatus(S419).