[Cryptography] Entropy is forever ...

[John Denker]

On 04/23/2015 04:38 AM, Thierry Moreau wrote:

> Another perspective perspective is to break down the analysis in two
> steps:
> 
> 1) You need the lessons from physicists before the digitizing sensor
> for the real world random process on which the hardware RNG relies.

OK.....

> 2) After the digital samples (numeric values) are taken, the system
> analysis turns to the Shanon information theory (and refinements like
> the Rényi entropy) with its limited definition of entropy.

Actually the physics entropy /is/ the computational entropy,
without limitation.  Checking the equivalence is simple in 
some cases and complicated in other cases, but it has been 
checked.

  Nitpickers note:
  a) The classical information (Shannon) corresponds to the
   classical physics (Boltzmann).
  b) In the exceedingly unlikely event that you are dealing
   with entangled Schrödinger cat states, you need to use a
   more sophisticated formula for the entropy ... same
   concept, fancier formula ... but even then the physics 
   entropy /is/ the computational entropy.  Unsurprisingly,
   you need to upgrade both sides of the equivalence.

> Despite the inter-relationships between the two steps, breaking down
> the analysis in two steps helps simple minded persons like me.

If you want to break it down into two steps, and 
delegate the first step to somebody else, that's
entirely reasonable.

However, it is not reasonable to prejudge the outcome of 
the first step.  In particular, it is not reasonable to 
squander the results of the first step by:
 a) Assuming differences with no basis in reality
  (Shannon versus Boltzmann), or
 b) Assuming equivalences with no basis in reality
  (entropy versus computational feasibility).