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Comment by Arnavion | Hacker News Reader

Because then it's obvious to everyone that Mick knows how to pass through the wall. Mick wants only the one reporter to be convinced that Mick knows how to pass the wall.

The point of zero-knowledge is that an external observer should not be able to be verify the proof, only the parties involved.

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>The point of zero-knowledge is that an external observer should not be able to be verify the proof, only the parties involved.

Had no idea from the story that was the point of a zkp

> Mick wants only the one reporter to be convinced that Mick knows how to pass the wall.

I can see how this could provide a justification, but this is not implied in the story at all.

"The Jealous Reporter" section is entirely about this. Start from "But the judges and the experts could not tell the tapes apart."

In particular:

>The reporter who had gotten the exclusive story had been convinced at the time that Mick Ali knew the secret, but the reporter could not pass his conviction on to the judges in court or to the television audiences either.

>Mick Ali had achieved his real objective. He wanted, in fact, to show that it is possible to convince without revealing, and so without unveiling his secret.

I don't get it. He can go left and come out right to demonstrate that he knows the secret - without revealing the secret. The reporter would still not know how he did it and could not pass his conviction on to the judges. And the fake reporter could still produce his fake report. The only reason for this complicated procedure I can come up with is that the secret includes some action at the fork which may not be observed by reporter.

> He can go left and come out right to demonstrate that he knows the secret - without revealing the secret

Correct

> The reporter would still not know how he did it

Correct

> and could not pass his conviction on to the judges

Incorrect, in this case he could pass on his conviction to the judges simply by showing them the tape where Mick goes in left and comes out right in a single unbroken take. Such a tape cannot be faked by the fake reporter.

> Such a tape cannot be faked by the fake reporter.

This is where I disagree. The second reporter will just tape the actor going in the left, editing magic, and observe him coming out the right. Both tapes will be indistinguishable.

In the original story the second reporter couldn't produce an unbroken tape between successive trials like the first reporter, so that can't be the litmus for proof.

That's basically a breakdown of the analogy.

If you want, you can forget about recording and tapes. Assume there was another person (unaffiliated with Mick or the reporter) standing next to the reporter while the experiment was being conducted. The rest of the story can stay the same. Mick also does not want this person to become convinced that Mick knows the secret.

Per the original story, this second person cannot know whether Mick coming out of the path that the reporter announces is a genuine display of Mick's ability or simply a collusion between Mick and the reporter. But if we go with the plan to observe Mick going in one path and out the other then this second person can become convinced of it.

> Such a tape cannot be faked by the fake reporter.

Well, at least that's the implicit assumption.

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