If a Fighter Writes a Paper to go for the Kill …

You don’t want to take on this man in the rink:

And you don’t want to take on his namesake in the scientific realm.

In my last post I wrote about the Kish Cypher protocol, and was wondering about its potential to supplant Quantum Cryptography.

The very same same day, as if custom ordered, this fighter’s namesake, no other than Charles Bennett himself, published this pre-print paper (h/t Alessandro F.).

It is not kind on the Kish Cipher protocol, and that’s putting it mildly.  To quote from the abstract (emphasis mine):

We point out that arguments for the security of Kish’s noise-based cryptographic protocol have relied on an unphysical no-wave limit, which if taken seriously would prevent any correlation from developing between the users. We introduce a noiseless version of the protocol, also having illusory security in the no-wave limit, to show that noise and thermodynamics play no essential role. Then we prove generally that classical electromagnetic protocols cannot establish a secret key between two parties separated by a spacetime region perfectly monitored by an eavesdropper. We note that the original protocol of Kish is vulnerable to passive time-correlation attacks even in the quasi-static limit.


The ref’s counting …

4 thoughts on “If a Fighter Writes a Paper to go for the Kill …

  1. Quantum Zealots are strange cattle. Always falling into bogs. What intrigues me is how they put quantum in front of everything they find interesting. Then they put the other word, classical, in front of everything that belongs on the ninth level of Hell.

    For the education of Mr Bennett, he may wish to read this paper:
    wherein I showed that there is no such thing as a classical domain.

    Ergo, there is no such thing as a classical channel.

    I am afraid that Mr Bennett is using entirely the wrong theory to analyse a real-world communication channel. I suggest that he learn some quantum mechanics.

    He may wish to ponder this also: The very first place we learned about quantum correlations was in the observation of anomalous specific heats in solids. That is a pretty gross effect, whose root cause is the symmetric versus anti-symmetric wavefunction choice. A moments pause to consider that and you would, if you were of a logical cast of mind, comprehend that quantum correlations are never absent.

    At that time nobody knew any quantum mechanics. They tried to model the statistical effects using classical theory and got entirely the wrong results. Gee, how about that?

    Moral of the story: use the right theory and you will get the right answer.

    Cautionary tale: A man may sound intelligent if he bellows and hollers with a cheering crowd at his back, but it pays to stop and think first before you take on an engineer.

    I am with the engineers on this one. I expect a good punch up. As a hedge fund guy, I do not even have to join the fight. I can just sip my Waikiki Mongoose in the box.

    1. Certainly hope Kish won’t take this laying down, but comes up swinging (academically speaking).

      It is certainly great to see this kind of attention, it is exactly what I’ve been hoping for. It was just strange that the Kish Cypher has been around for so many years without this kind of scrutinization.

      Theoretical computer scientists are fond of proving certain properties. And this is all fine and dandy as long as the theory fully captures all aspects of the experimental scheme. I didn’t work through Bennett’s paper yet, but I think the most critical attention has to be focused on the assumptions that he makes (explicitly as well as implicitly).

        1. The manuscript
          is submitted to a journal for publication. While there have been measurement-science-based security proofs also in earlier papers, now the security proofs are in the language that is familiar in the physical crypto field. The unconditional security is evaluated in terms of statistical distance and “epsilon-security” measures. We are grateful for Bennett-Riedel that they forced us to do these studies. Earlier, we felt these were less important because the information theoretic security was obvious due to the results. However, it is important to translate the results to the language of those in other fields who may want to use them. We are happy that it is finally done.

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