You probably will be getting at least one bit of randomness out of it if the input is not saturated (As in not below 0 or above reference voltage ADC is using),

You probably will be getting at least one bit of randomness out of it if the input is not saturated (As in not below 0 or above reference voltage ADC is using), just because pretty much all ADC are noisy enough that the last bit will be flipping. Of course that doesn't excuse every other problem with it > Meaning that there is no hardware security whatsoever and it's trivial to extract all your keys from the device if you ever lose it. Whoops. Most micros, ones used in various Arduinos included have fuse bits so there is at least the minimal level of protection. Question whether they used it even...