[Cryptography] Entropy Needed for SSH Keys?

[Sampo Syreeni]

On 2016-05-27, Ray Dillinger wrote:

> IIRC, one nanosecond was once defined to me as the approximate amount 
> of time it takes for light to travel fifteen centimeters.

In vacuum (and mostly in dry air), you can calculate it to be exactly 
299792458 m/s * 1e-9 s ~= 30 cm. So about a foot is the basic rule. No 
need to remember any of that, you can get it straight from Wikipedia.

In silico it's more complicated, because of the varying dielectric 
constant of different kinds of doping levels, surface structure, stray 
capacitance, and whatnot. But based on what I've seen of the possible 
permittivities, I'd wager the nanosecond can range anywhere from 28cm 
downto as little as 2cm, depending on the substrate.

> Does this matter much, in terms of creating useful interference 
> patterns?

In interference, it matters downto the twelth digit.
-- 
Sampo Syreeni, aka decoy - decoy at iki.fi, http://decoy.iki.fi/front
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