Software is not enough. Use an old 16 bit home computer, inside a Faraday cage, inside an airtight enclosure, powered by a stack of lead-acid batteries (don't want them to get in through the power lines). Now, construct a pneumatic braille terminal, place all the pumps and valves inside the enclosure, enclose the pressure lines inside a thick padded pipe and embed the actual terminal inside a thick block of foam with slits for your hands.
This won't protect you from brainwave readers, but it will contain any and all treacherous waves and vibrations from your computer.