Confused with color abstraction in this video.

Bob has:

  • public color;
  • mixture from Alice;
  • can produce random color;

Eve has:

  • public color;
  • mixture from Alice;
  • can produce random color (why not?);

Bob can produce same shared color as Alice did, Eve cannot. Does it make sense?


Bob has his private color and mixture from Alice. When he mixes them up he has the same color as Alice when she mixes up mixture from Bob and her private color.

Eve has only two mixtures but no private color, so she can't produce the same color as Alice and Bob.

Eve here can only see colors Alice and Bob exchang but can't change them (Eve is for eavesdropper), if she can change them (intercept mixture from Bob and send her mixture instead) she should be called Mallory (from man in the middle). In this case we have to assume that Alice knows Bob's mixture - he showed it to her earlier in real life or something - and she won't be tricked by fake mixture Mallory sent her.

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  • $\begingroup$ Forgetting about the real Diffie-Helman procedure: Bob's private color is a random color. So Eve could produce her private color as a random color. Smth like this: if Bob's private color + Alice's mixture = Shared secret so Eve's private color + Alice's mixture = Shared secret $\endgroup$ – barantaran Jan 16 '18 at 18:26
  • $\begingroup$ Edited my answer - is it clearer now? $\endgroup$ – Przemko Robakowski Jan 16 '18 at 18:39
  • $\begingroup$ Still trying. So the question for this kind of diagram drive.google.com/file/d/15U2RedQ00okrsML-WbOOfXl8ftaOX2GR/… "who can not produce dirty-green?" isn't right? PS. Eve doesn't know, that it has to be dirty-green, but Alice does? $\endgroup$ – barantaran Jan 16 '18 at 18:55
  • $\begingroup$ My private color for Alice and My private color for Eve are two different colors, so only Alice and Bob can produce combination Alice's private color+Bob's private color+public color $\endgroup$ – Przemko Robakowski Jan 16 '18 at 18:59
  • $\begingroup$ Can we say, that palette, used by Alice and Bob automatically leads to equvalent colors after final mix, but it is dramatically hard for Eve to guess which color exactly? $\endgroup$ – barantaran Jan 16 '18 at 19:14

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