| 摘要 |
PURPOSE:To protect more completely the secrecy of a file device by providing a comparison detecting section and a switch section or the like and detecting the presence of an encoding key used for the secrecy protection, thereby making an encoding command ineffective when no encoding key is present. CONSTITUTION:A command from a CPU26 is registered to an encoding command register 28 via a file control section 22 and an encoding/decoding control section 23 when a secret data is written to a file device 27 via a file processing unit 21 from a CPU26 while being encoded. When an encoding key exists in a data passing through a signal line 101 from the CPU26 and an encoding key storage section 24 stores the encoding key, the data is encoded via an encoding/ decoding section 25 and switching sections 30, 31 and the encoded data is written in the device 27. When no data is written in a storage section 24, an encoding disable error is detected by a comparison detection section 29, the encoded command is made ineffective and it is reported to the CPU26 and the control section 22 or the like. Thus, the encoding by an incorrect encoding key is prevented and the protection of secrecy of the file device is made completed. |
