The 4th video in this series, covering random numbers and how to generate them.
One more note about the diode diagram: it would have been more clear if I'd put in the polarity signs. The negative pole is on the left, and the electrons are repelled by it, meaning they're trying to move across the diode to the right. That particular diode is reverse biased, which SHOULD make that the equivalent of an open circuit. But the diode is so small that the electrons can tunnel through via quantum mechanics, resulting in a signal that can be used as a source of entropy. Here's more about diodes, including a diagram showing what happens with reverse bias: https://learn.sparkfun.com/tutorials/diodes
GNU Privacy Guard: https://www.gnupg.org/
The Android Bitcoin wallet flaw http://android-developers.blogspot.com/2013/08/some-securerandom-thoughts.html
