| 摘要 |
PROBLEM TO BE SOLVED: To prevent a digital data from being illegally copied. SOLUTION: A data B as a part of a bit stream and a key K stored in a memory 31 are calculated by a calculation circuit 32 to obtain a 1st block and a 2nd block in position. The LSBs of DC differentials of the 1st block and the 2nd block specified by the calculation circuit 32 are read out by a detection circuit 33, and are stored in a memory 34. Whether or not the two stored values in the memory 34 are coincident with each other is decided by a decision circuit 38, and a result of the decision is outputted to a control circuit 39. Upon noncoincidence of the two values, 'the bit stream is due to copy' is displayed on a display device 40, and simultaneously, recording operation of a recording device 37 is inhibited. |
