The scheme I proposed (rather vaguely) is based on the idea of, sort of, an "immune system" for computers, based on "friend vs foe recognition" of code. Essentially, hardware is made available to perform such recognition, and then only "friendly" code is runnable. Thanks to the wonders of PKC, it is infeasible for anybody who does not know your secret key, to create code you will consider friendly. Of course, yes, if somebody can con you into declaring some code is friendly, then you lose. Or, if they can get to you reveal your secret keys. Or, if your computer was already penetrated on day 1 due to hardware or software hacks pre-inserted during manufacturing. One could also imagine multilevel protection where there are multiple levels of friendliness, the higher levels being allowed to access more features of the computer. Is this worth doing? I do not know. Should we declare it all to be a lost battle?