US Patent 8001377 Methods and apparatus for secure data processing and transmission

Methods and apparatus provide for placing an apparatus into at least one of a plurality of operational modes, wherein: the apparatus includes a local memory, a bus operable to carry information to and from the local memory, one or more arithmetic processing units operable to process data and operatively coupled to the local memory, and a security circuit operable to place the apparatus into the operational modes; and the plurality of operational modes includes: (i) a first mode whereby the apparatus and an external device are operable to initiate a transfer of information into or out of the memory over the bus, (ii) a second mode whereby neither the apparatus nor the external device are operable to initiate a transfer of information into or out of the memory over the bus, and (iii) a third mode whereby the apparatus is operable to initiate a transfer of information into or out of the local memory over the bus, but the external device is not operable to initiate a transfer of information into or out of the local memory over the bus.