  We propose a disk encryption method, called secure disk mixed system (SDMS)
in this paper, for data protection of disk storages such as USB flash memory,
USB hard disk and CD/DVD. It is aimed to solve temporal and spatial limitation
problems of existing disk encryption methods and to control security
performance flexibly according to the security requirement of system. SDMS
stores data by encrypting with different encryption key per sector and updates
sector encryption keys each time data is written. Security performance of SDMS
is analyzed at the end of the paper.
