The cr.yp.to microblog: 2018.03.22 23:53:42

2018.03.22 23:53:42 (976955103587590149) from Daniel J. Bernstein, replying to "Frédéric Grosshans (@fgrosshans)" (976950136868925442):

Cages and shields are _not_ the same thing (see, e.g., https://people.maths.ox.ac.uk/trefethen/chapman_hewett_trefethen.pdf), and cages make the general QKD security issues easier to visualize. The bigger problem in this discussion is the constant switching from one bullshit claim to another.

Context

2018.03.22 23:11:28 (976944476437565440) from "Frédéric Grosshans (@fgrosshans)":

Let look at the metallic mirror case: Suppose you send a plane wave straight to a metal sheet. Maxwell equation tels you that the wave goes through the mirror. But this wave excites electrons in the metal, who themselves reemit other waves. One is the reflect wave. The other...

2018.03.22 23:17:24 (976945970687741952) from "Frédéric Grosshans (@fgrosshans)", replying to "Frédéric Grosshans (@fgrosshans)" (976944476437565440):

… propagates along the same direction of the original wave & is dephased by π. If the metal sheet is thick enough, it has the same amplitude and the detector behind the sheet will measure E=sin(ωt)+sin(ωt+π)=sin(ωt)–sin(ωt)=0. (Linearity of MAxwell eq ⇒ we add the two waves)

2018.03.22 23:27:09 (976948423319523328) from Daniel J. Bernstein, replying to "Frédéric Grosshans (@fgrosshans)" (976945970687741952):

Show me any allegedly "thick enough" EM shield and I'll show you a (very expensive) detector array that sees through the shield. You'll then switch to another bullshit example without admitting you were wrong, the same way that you've switched away from the Faraday-cage example.

2018.03.22 23:33:58 (976950136868925442) from "Frédéric Grosshans (@fgrosshans)":

I did not switch to antoher example: a Faraday cage and a metallic mirror are the same thing, operating through the same mechanism (conductive material wich is continuous at wavelength scale + Maxwell equations), just at different frequencies (optics vs radiowaves).