A method of distributing an encryption key for protecting a broadcasting service that is broadcast to a terminal in a broadcasting system, comprising the steps of: generating, by a broadcasting network, a first attribute value pair for deriving a traffic encryption key, TEK, in response to providing the broadcasting service to the terminal, and generating and transmitting a first long term key message including the first attribute value pair to the terminal; and generating, by the broadcasting network, a second attribute value pair for deriving the TEK before a lifetime of the first attribute value pair expires, and generating and transmitting a second long term key message including the second attribute value pair to the terminal, wherein a plurality of TEKs including the TEK are derived from the first attribute value pair and the second attribute value pair and the first attribute value pair and the second attribute value pair are derived from at least one key seed pair, KSP, composed of KS 1 , KS 2 arbitrarily generated in the broadcasting network, wherein the TEK is calculated based on a hash value of KS 1 to which a hash function is applied and a hash value of KS 2 to which a hash function is applied, and wherein the first long term key message and the second long term key message includes content access rules, and when said content access rules are defined with respect to single content encrypted by one or more of the plurality of TEKs, the first long term key message includes a field indicating whether traffic key descriptors belong to the first long term key message, a field indicating the number of the traffic key descriptors, a field defining the traffic key descriptors including access criteria and parameters related to one or more other TEKs, a field indicating a TEK sequence number which indicates a first TEK sequence among a plurality of TEK sequences to which the traffic key descriptors are applied, and a field indicating a TEK sequence number which indicates a last TEK sequence among the plurality of TEK sequences to which the traffic key descriptors are applied. generating, by a broadcasting network, a first attribute value pair for deriving a traffic encryption key, TEK, in response to providing the broadcasting service to the terminal, and generating and transmitting a first long term key message including the first attribute value pair to the terminal; and generating, by the broadcasting network, a second attribute value pair for deriving the TEK before a lifetime of the first attribute value pair expires, and generating and transmitting a second long term key message including the second attribute value pair to the terminal, wherein a plurality of TEKs including the TEK are derived from the first attribute value pair and the second attribute value pair and the first attribute value pair and the second attribute value pair are derived from at least one key seed pair, KSP, composed of KS 1 , KS 2 arbitrarily generated in the broadcasting network, wherein the TEK is calculated based on a hash value of KS 1 to which a hash function is applied and a hash value of KS 2 to which a hash function is applied, and wherein the first long term key message and the second long term key message includes content access rules, and <EOS>