[Cryptography] Proper Entropy Source

[Mansour Moufid]

On Mon, Jan 20, 2020 at 6:14 PM Ryan Carboni <ryacko at gmail.com> wrote:
>
> I think relying on a combination of futex and ram latency benchmarks
> would be enough to provide a reliable source of entropy.

You mean source of randomness, entropy is the measure of randomness.

Given two finite schemes A and B, the entropy of the product AB is
H(AB) = H(A) + H(B|A).

If A and B are independent then H(B|A) = H(B) and H(AB) = H(A) + H(B).

It is always true that H(B|A) <= H(B).

In the worst case, B is deterministic, then H(B|A) = 0 and H(AB) = H(A).

The proof of this property is in the first chapter of "Mathematical
Foundations of Information Theory" by Khinchin.

In other words, software can never increase entropy, at best it
contributes nothing.