When selecting a source of randomness it is essential to understand whether the randomness of the source is caused by an integral property of the system itself, or if the source really is ‘just’ a measure of events external to, and unpredictable by, the system itself. The former is typically called ‘intrinsic’ randomness, the latter has different names but since the ‘signal’ in question is typically not part of the ‘desired’ operation of the system, in this whitepaper we shall refer to it as ‘external noise’. The difference is important, since, by definition, sources of intrinsic randomness cannot be influenced by an adversary, whereas sources using external noise can typically be influenced. In reality, of course the boundary between these types of sources is not as black and white as the definition suggests. Take, for instance, thermal noise as an example. Although this noise is present in all semiconductors, an adversary still has influence over it, by changing the temperature of the semiconductor. However since he does not have total control over it (unless he cools the system to 0K), thermal noise is still typically considered a source of intrinsic randomness.