| 摘要 |
PROBLEM TO BE SOLVED: To make surely detectable an alteration of reproduction restriction information, and to inhibit reproduction at the time of detecting an alteration. SOLUTION: The hash value of a reproduction restriction value group 70 is calculated prior to a reproducing operation by a hash calculating circuit 71, and the obtained hash value is held in a memory region (72 and 73) which can not be viewed from the outside. The previously calculated hash value is compared with this time calculated hash value by a coincidence detecting circuit 74, and the presence or absence of alteration is detected according as whether or not those hash values are made coincident. When an alteration is detected, a control part 75 writes an alteration detection flag based on the output of the coincidence detecting circuit 74, and inhibits the reproducing operation. Also, in the case of reproduction restriction, the reproducing operation is inhibited regardless of the presence or absence of alteration. |
