DIGITAL SIGNAL RECORDING AND REPRODUCING APPARATUS, TRANSMITTER-RECEIVER, AND METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To provide an apparatus and method capable of minimizing the number of accesses to a recording medium and a transmission channel for decryption in the case of reproducing a digital signal, so as to relieve the load on its reading and more effectively protecting the copyright. SOLUTION: The apparatus reproduces a digital signal and key information used for decrypting the digital signal from the recording medium and creates an encryption key on the basis of the reproduced key information to decode the signal for the first time. The apparatus uses the key information for an initial value and repeats the arithmetic operations to sequentially obtain new key information and updates the encryption key on the basis of the new key information to decode the signal. Further, the apparatus analyzes whether or not an I picture is included in a video signal to be recorded and records the analysis result to a management information area in the recording medium. The apparatus reads the management information at special reproduction and reproduces only the I picture. COPYRIGHT: (C)2004,JPO