The Devil is in the Details
1. Precisely how this Fort Knox circuitry "isolated"? Logically, it cannot both be truly isolated and effectively-functional, since some communications channel is required through which to receive secrets to be stored, to send secrets when presented with a correct key, to receive keys, and possibly to send information as part of a handshake protocol.
2. There are persistent rumors/myths/urban legends/&c. that the physical Fort Knox (technically, the "United States Bullion Depository") is an empty building, kept in-commission merely for appearance' sake. Samsung's electronic Fort Knox may be a similar red herring.
3. "If you wish to kill the general, you first must shoot his horse." Were I attempting this, !'d try social-engineering in an engineering change order defining a new machine-specific, write-only register which upon receipt of a particular bit-pattern, enabled kernel-mode access for the current process.
(Icon for Fort Knox conspiracy theories.)