We looked at encryption in the section Keeping your conversations secret with encryption in Chapter 4, Wi-Fi Pranks - Exploring Your Network; however, the key to secure cryptography is entropy—a high-quality source of randomness.
Most random numbers used in computer programs are pseudo-random, which means they are generated in a predictable manner using mathematics. In many circumstances this is fine, but for strong cryptography, this is may not be suitable, even with a good random seed, so we need a True Random Number Generator (TRNG).
Usually, this requires expensive hardware, or weird physical events such as noise analysis to generate random number using a high level of entropy. But did you know that your Raspberry Pi—including the Pi Zero—also contains a hardware-based TRNG?