| 摘要 |
PURPOSE:To protect the information from a reference request given from a malicious person for reference of the information by permitting the reference to a momory area different from a memory area of a reference destination to a request given from a non-permitted person to the reference of information and thus pretending that the reference request succeeded. CONSTITUTION:When a request is given for reference to a protecting area 11 by means of a password number 100 and a reference destination address 101, the contents of a password number 13 are compared with the number 100 by a comparator 15. If this comparison fails, the output of the comparator 15 is set at ''0'' and then turned into ''1'' via an NOT circuit 16 to be supplied to an AND circuit 17. Then the contents of a number 12 storing the range of the area 11 are compared with the address 101 by a comparator 14. When this comparison succeeds, the output of the comparator 14 is set at ''1'' and supplied to the circuit 17. Therefore the output of the circuit 17 is set at ''1'' and a selection circuit 19 selects the output of a non-protecting area 18 and supplies the output signal as an address of the area 11 storing the protecting area for access. |
