A portable device for connecting to a host information processing platform includes: a digital information storage medium storing an operating system image, secure data, applications, and system state of an owner of the portable device, wherein the medium is in read only mode until a set of tests are run on the host platform; and a platform validation program for: running the plurality of tests on the host computer to determine whether the host is safe, depending on the outcome of the tests, presenting the owner with a user-identifiable message, prompting the owner to enter decryption credentials, and receiving the decryption credentials. The portable device could also optionally include subsystems that provide additional functionality to the owner such as media playback, communications, and entertainment.