A storage system comprising a secured storage device characterized in that the secured storage device comprises: a storage module comprising a secured disk of arbitrary size comprising a digital key area in which a digital key is stored and a secured data area that is encrypted with said digital key; a kernel layer module that deactivates said secured disk in a security setting mode, and activates said secured disk by said digital key in a security setting release mode; and a key application module that mounts a secured disk sub-system , which processes input/output requests for said activated secured disk, to an application module that can manage data stored in said storage module at a security setting release request by execution of a key application that comprises a digital key that is identical to said digital key; controls said kernel layer module and activates the secured disk by the digital key of said key application, which is identical with the digital key stored in the digital key area of said secured disk; and processes input/output requests for the data stored in said activated secured disk through said kernel layer module wherein said key application module comprises: a digital key storage that comprises a digital key that is identical to the digital key stored in the digital key area of the secured disk ; a service executor that is activated at execution of said key application, installs a secured disk processor at said kernel layer module , activates said secured disk by said digital key at setting of user password and input of the set user password, and processes input/output requests to said secured disk; and a service execution monitor that monitors said service executor , sets up said security setting mode at occurrence of an event forcefully terminating the service executor , unmounts said secured disk sub-system from said application module and terminates the service executor . a storage module comprising a secured disk of arbitrary size comprising a digital key area in which a digital key is stored and a secured data area that is encrypted with said digital key; a kernel layer module that deactivates said secured disk in a security setting mode, and activates said secured disk by said digital key in a security setting release mode; and a key application module that mounts a secured disk sub-system , which processes input/output requests for said activated secured disk, to an application module that can manage data stored in said storage module at a security setting release request by execution of a key application that comprises a digital key that is identical to said digital key; controls said kernel layer module and activates the secured disk by the digital key of said key application, which is identical with the digital key stored in the digital key area of said secured disk; and processes input/output requests for the data stored in said activated secured disk through said kernel layer module a digital key storage that comprises a digital key that is identical to the digital key stored in the digital key area of the secured disk ; a service executor that is activated at execution of said key application, installs a secured disk processor at said kernel layer module , activates said secured disk by said digital key at setting of user password and input of the set user password, and processes input/output requests to said secured disk; and a service execution monitor that monitors said service executor , sets up said security setting mode at occurrence of an event forcefully terminating the service executor , unmounts said secured disk sub-system from said application module and terminates the service executor . <EOS>