Mutual authentication apparatus and method in downloadable conditional access system

A mutual authentication method in a DCAS, the mutual authentication method comprising:

• receiving authentication-related information about authentication between an authentication unit and an SM from a TA;
• generating an authentication session key using the authentication-related information;
• transmitting the authentication session key by the authentication unit to the SM through a CMTS;
• and
• controlling a CAS software to be downloaded to the SM from the authentication unit, when the authentication is completed by the authentication session key.

A mutual authentication method in a DCAS, the mutual authentication method comprising:

• periodically signing software client-related information using a private key of an authentication unit, and transmitting the software client-related information to an SM;
• encrypting a first message by the SM, and receiving the encrypted first message, the first message including session identification information (session_ID), an SM certificate (SM_Certificate), and host identification information (Key_Pairing_ID);
• performing digital signature verification and decryption of the encrypted first message, and transmitting a second message to a TA, the second message being generated by digitally signing and encrypting the decrypted first message;
• performing digital signature verification and decryption of the second message by the TA, digitally signing a third message, outputted using the decrypted second message, using a private key of the TA, and receiving the third message encrypted by applying a Secure Sockets Layer (SSL) scheme using a public key of the TA;
• performing digital signature verification and decryption of the encrypted third message, configuring a fourth message, digitally signing and encrypting the fourth message, and transmitting the encrypted fourth message to the SM, the fourth message being configured by combining the session identification information, the session generation information, and validity verification information from the decrypted third message;
• performing digital signature verification and decryption of the encrypted fourth message by the SM, and receiving a fifth message from the decrypted fourth message, the fifth message including a first session key, the session identification information, a secret key (Ki), and the session generation information, and the first session key being generated by any one of the third messages and a first SM identification number (NONCE_SM);
• performing digital signature verification and decryption of the encrypted fifth message, and generating a second session key using information included in the decrypted fifth message, the first SM identification number, and information included in the third message with respect to same session identification information;
• determining whether the second session key is identical to the first session key;
• generating an initial vector (IV), and encrypting a second SM identification number (NONCE_SM+1) using the IV and the second session key based on an encryption scheme using the public key of the TA, the second SM identification number being obtained by increasing the first SM identification number;
• and
• encrypting a sixth message using a public key of the SM, and digitally signing the encrypted sixth message and the first SM identification number using the private key of the authentication unit, the sixth message including the session identification information, the second SM identification number, and the IV.

A key generation method for mutual authentication in a DCAS, the key generation method comprising:

• receiving an initial key seed value (Kc) and a random value (RAND_TA) required for generation of a session key through a TA, the initial key seed value being generated by inputting a secret key (pre-shared key) previously shared by an SM and the TA;
• receiving first information including a unique number (SM_ID) of the SM received from the SM, the initial key seed value (Kc), the random value (RAND_TA) randomly generated by the SM, hardware version information of the SM, and software version information of the SM;
• processing the first information using a hash function;
• defining second information, processed by the hash function, as a master key;
• processing the second information using a random function;
• and
• selecting a predetermined bit from the second information, processed by the random function, and defining the selected bit as the session key shared by the SM and an authentication unit.