For phones it is possible to slide load a new OS that was built by you to include various secure options. At least that was possible a few years back when I looked at that subject. So you can limit what is installed; where it is installed, etc. I buy cell phones for use that are not locked so I have the ability to use what Cell network I chose (assuming the my hardware is compatible with their network). My current phone is a google Pixel 3a, the low cost google phone. For support for hacking the phone to get it to do what I want I would head over to
https://forum.xda-developers.com/pixel-3aFor phones that don't want to just use cell phones for communication and their 10 year old laptop is pushing up daisies, a Raspberry Pi 4b might be worth looking at.
I have been testing a new version of the Raspberry PI 4B and have found that the new hardware upgrade performs fantastic...for a sub 40 dollar pico computer. There is one known problem with compatibility with USB Type-C cables. Also the device can be a bit of a power hog compared to older versions. So the right power supply is needed.
The other problem is that the device dose run hot in the approved RP4B case. No real worries for danger to hardware, the RBP4 will slow down during heat management. A small fan / heat sink can be added to let the RB4B run longer at turbo speed. So if you are looking for a computer than can do some simple word processing, surf the web; and watch you tube videos in low res, this might be an option.
So what has this to do with secure communications? With a bit of work it is possible to tie two Raspberry PI computers over a normal network and secure your data transfers. This hardware solution does not offer anything unique over running Linux on a laptop. Other than the fact that the hardware is dirt cheap and very small.
The hardware small enough to use double sided tape to stick it to the back of your current monitor for use. Versions of the RBP4 differ by the amount of ram that is installed. (1, 2, and 4 gig models can be found, with the 4 gig models in short supply)
My current project is to see if I can use the RBP4B along with an old LCD display to provide access / control over 2 video security cameras. In the past I have used various older Raspberry PI computers for NAS (network attached storage), print server, media server. As a print server it worked fine, the old RBPi 2 was too slow to be used as a NAS controller, but it did work. As a media server once the channel was locked in the quality of the output was fine. ROKU and other dedicated devices have a better user interface and work better on streaming data sources.
ecuritysay ancay ebay oneday inyay anymay ifferentday aysway . otnay ustjay ithway ardwarehay .
"Security can be done in many different ways. Not just with hardware."