On Thu, Oct 17, 2013 at 02:39:01PM -0700, Jon Callas wrote:
It is certainly true that radioactivity is a random effect, and is quantum in nature. That does not mean that in order for a random sampling to be quantum, it must be based on radioactivity; there are other quantum sources of randomness. Noisy diodes, resister noise, CCD noise, etc. are all quantum. If you want to get picky, *all* physical effects are quantum, even ones that aren't usefully random. There is nothing magic about one physical source or other that makes it more suited for crypto. Thinking that a hardware source should be radioactive is affirming the consequence, as well.
Radioactivity is almost uniquely insensitive to tampering through environmental
influences, though, owing to the large energy scale of nuclear processes [1].
Unfortunately, it does not automatically follow that the circuit used to
detect it is also similarly robust, and NSA would probably be able to
easily develop the capability to eavesdrop on Geiger-counter based RNGs
if they become widespread. A high DC voltage, and abrupt current pulses -
this is sounding rather similar to a spark-gap transmitter.
[1] A handful of exceptions exist involving low-energy beta decays, such as
Dy-163 and Re-187.
--
Andrea Shepard