A secure storage device is connected to a computer system. The secure storage device has a memory including a domain and a subdomain storing first and second data, respectively. The computer system includes a first level hypervisor managing a first level virtual machine, which supports a first operating system, and a second level hypervisor. The second level hypervisor manages a second level virtual machine, which supports a second level operating system. A first authentication process for the first level operating system uses first profile data sent by the computer system and a portion of the first data. A second authentication process for the second level operating system uses second profile data sent by the computer system and a portion of the second data. The first data is not accessible by the second level operating system. The second data is not accessible by the first level operating system.