Thermal noise random I'm working with a Cortex M0 SoC that integrate an "RNG" (not specifically claimed as TRNG), that is however claimed to be "suitable for encryption". It works using thermal noise measurements.
Knowing the whole SoC retails for less than $10, my wonder is: if it is that good, why isn't it more widespread? In particular, why is it not available on the PC platform. I read that Intel used something similar, but it is no longer in use.
Since the whole RNG should probably be analyzed to determine if it's any good, my question is more like: "Can thermal-noise be used for a TRNG ?"
A true random number generator (TRNG) usually consists of two components: an “unpredictable” source with high entropy, and a randomness extractor — a function which, when applied to the source, produces a result that is statistically close to the uniform distribution. When the output of a TRNG is used for cryptographic needs, it is prudent to assume that an adversary may have some (limited?) influence on the distribution of the high-entropy source.

Thus it takes a bit of work to obtain randomness and there are many pitfalls.

If it's done well, the statistical randomness of the extractor’s output can be proven, and is not based on any unproven assumptions, such as the security of cryptographic hash functions. On the other hand output rates may be slow, and ensuring outside physical influences are thwarted may not be always possible. Obviously thermal noise in a circuit may be influenced by other factors.