Pick a number, any number! Was it 2348239324818238123492349052348238? Choosing a long, truly random number is very important for crypto functions and messing it up can cause a lot of problems. Recently, the country of Estonia had to withdraw all their digital ID cards because of a weak random number system that enabled numbers to be guessed easily.
All the Afero secure IoT devices contain a Hardware Security Module that contains a high-quality random number generator, required for all crypto functions to be secure. Do not rely on software to do this important job.