Patent ID: 8307455

Claim:
A decryption-key distribution method for distributing a decryption key to a radio terminal in a radio communication system, wherein a contents server sends data encrypted with an encryption key, which is received from a control unit managing the encryption key and/or the decryption key, to the radio terminal through a broadcast channel, wherein the radio terminal decrypts the received data with the decryption key corresponding to the encryption key, and wherein a terminal authentication and an authorization for content distribution based on authentication, authorization and accounting (AAA) are performed, the decryption-key distribution method comprising: storing, in a decryption-key database of an authentication unit, a content type or content identification information, decryption keys, and valid periods of the decryption keys in correspondence with each other, wherein the content type or content identification information, and the corresponding decryption keys and valid periods of the decryption keys are received from the control unit, wherein the authentication unit performs an authentication step of receiving, by the authentication unit, a terminal authentication request message from the radio terminal, the terminal authentication request message including a terminal identifier and an authenticator calculated using the terminal identifier for verifying an adequacy of the radio terminal, and performing the terminal authentication, and wherein if an authenticator obtained according to the terminal identifier matches with the authenticator included in the terminal authentication request message, the authentication unit further performs: an authorization step of referring to a content registration database to obtain the corresponding content type or content identification information, according to the terminal identifier included in the received terminal authentication request message, wherein the terminal identifier and the content type or content identification information of a content which the radio terminal can receive are stored in advance in correspondence with each other in the content registration database; a step of referring to the decryption-key database, according to the obtained content type or content identification information, to obtain a specified-in-advance number of the corresponding decryption keys and a specified-in-advance number of valid periods of the decryption keys; and setting, by the authentication unit, the obtained specified-in-advance number of decryption keys and the valid periods of the decryption keys in a terminal authentication response message which is a response to the terminal authentication request message from the radio terminal, and sending the obtained specified-in-advance number of decryption keys and the valid periods of the decryption keys by sending the terminal authentication response message to the radio terminal or to a packet control unit.