My goal is to have two separate systems where one is secure even if the second one is full of malware. My current approach is to have two separate laptops and the only way these two communicate with each other is by sending text messages (no files) to each other via email - this kind of minimal text-based communication is a necessity.
I will travel a lot and thought about how I could lighten my pack.
Option 1: Since it is easy to swap out the SSD on the more powerful laptop, I could simply carry two SSD drives (one with the secure system and the second one with the less secure system). What I think I know: The two drives share the RAM and the BIOS. They also share the input devices, the display and a number of other hardware modules but I guess that is less relevant here. Did I overlook anything here?
Option 2: Same as option 1 but I would boot into the "secure operating system" from a USB stick while the less secure hard drive is still plugged in. This would be less effort but would it provide the same level of security?
Option 3: Same as option 1 but I would swap out the RAM also.
Option 4: Allow a raspberry pi to use the display and the input devices of my laptop without "getting in contact" with the RAM, the hard drive etc of my Laptop. Is that possible?
My questions are:
a) Is there another option? Which option provides the best balance between security, weight savings and least (one time and ongoing) effort?
b) For the option you would suggest: What are the remaining security holes? How rare/difficult would a successful attack be and how does the security level compare to the existing baseline security (the "secure system" is online and receives text-based emails from the less secure system - I can not change this)?