Comment depends on what you want to accomplish (Score 2) 117
You're probably not going to make anything close to what you're using, but if you're looking to build something more modest, that's definitely possible.
It really depends on what your goal is, and how advanced of parts you're willing to accept as a starting point. Ben Eater (https://eater.net/) has a guide on building an 8bit computer from low level gates. It's a really good basis to be able to build some primitive devices that would be capable of something a little more advanced. I'm building a 16 bit version, with a display and keyboard. If one was interested, they could definitely build off something like this, adding encryption and a network interface that would allow them a fairly trustworthy device.
Another approach that you could take is auditing the devices you use. There are guides on how to go from XRays of chips to decoding them. Ken Shirriff is a ninja at this, and I HIGHLY recommend his talk: https://www.youtube.com/watch?...