We all want to be able to communicate with each other in total privacy. So we need lots of good random numbers to do that using cryptography. And true random numbers are the most secure. We’ll show how to make entropy sources using simple and commonly available components like Zener diodes. These can then be the foundations of your own true random number generators (TRNGs) you can rely on to not have been compromised by governments or their agencies. Or in a nutshell, something like the things below. So, why should you build a TRNG?