A portable computer providing high level of security comprises of two completely logically and electrically isolated computer modules within one tamper resistant enclosure. One computer module is for Higher-Security applications (refer higher-security to as “red”) and the other is for Lower-Security applications such as email and internet (refer lower-security to as “black”). The two modules are coupled together to secure Peripheral Sharing Switch that enables intuitive user interaction while minimizing the security risk resulted from sharing same peripheral device.