| 摘要 |
PROBLEM TO BE SOLVED: To prevent illegal viewing and copying by transmitting a scrambled bit stream and the encrypted key used for the scrambling through mutually different paths, and descrambling the bit stream after decrypting the encrypted key with a smart card. SOLUTION: A demodulation and error correction part 1 performs demodulation and RS decoding for an analog broadcast signal. An ATV decoder 2 descrambles the output of the correction part 1 according to descrambling information. A copying preventive process part 4, on the other hand, separates a scrambled recording signal into a bit stream and a key stream, and encrypts the key stream. Then the smart card 3 decrypts the encrypted key stream separated by the process part 4 and the index code of the ATV decoder 2 and outputs descrambled information KS to the decoder 2. Therefore, authentication and key exchange are performed automatically to prevent illegal viewing and copying. |
