So here we are again, explaining
the principles upon which des is designed. Yes it’s the nth time; and the same caveat as before: go anywhere else to learn someone’s description of the algorithm. Here we motivate the design.
So imagine you are studying the infamous quantum mechanics 2 hole screen – separating electron gun on the left from intensity screen. Or the 1 hole. Or the two holes shifted up (or down) a bit on the grate.
Oh and don’t forget that we can flip the grate, should we want the gun on the right (and the screen on the left).
After all like des, quantum mechanics is inevitably reversible, since “information” is conserved.
Now imagine that the e function of des is the grate.
And 2 of the six input bits of the current sbox are the slits in the grates.
The purpose of the way the e function shift inputs left (and right) is to simulate shifting the slits in the grate ip and down.
So that the qm normal density is shifted.
Our goal is to uniformly fill an intensity space, on the screen. Or better, average the left and right intensity screen (per the classical functional form.
Now, even though we shift our normal curve up and down (as the number of supports in the pair wise plaintext’s chats induce a key particle to move 1,2 3… lambada from the center, within the normal curve (and while constructing/destructing as we go) we still need the addition of intensity curves to uniformly fill the output space.
And here is where comes in the particular key schedule. It’s particular sequencing moves the grate around not only so feistels multiplexor covers all subpace but does so in such manner that guarantees that the concentration of intensity at any point (in 2d intensity space) is never more than the second eigenvalue gap.
Now recall that des does not have reversible sboxes. But we don’t need them! After all we have interleaved diffraction grates, since left 2 right we have half s des round and (right 2 left) we have the other half.
Now view the des subkey generatio functions own (highly programmed) bit duplication as a means of subtly (at huge granularity) measuring the quantum effect, thus influencing just how the left and right particle motions occur – giving a characteristic.
And ensuring that there exists no matrix representation of the same graph.