http://qs321.pair.com?node_id=11136249


in reply to Reverse download protocols [solved]

This reminds me of authentication protocols in cryptology, where the one-way-encryption keys are never exchanged.

A sends a sequence of random values and B must reply with the correct encryption or just a property of it. After n correct answers A will be statistically "convinced" that B had the correct key.

Because of the asymmetric nature the correct key can't be deduced by a listener in the middle.

I doubt it helps, but the question allows so many wild interpretations...

- Ron

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Re^2: Reverse download protocols
by tomasz (Acolyte) on Aug 30, 2021 at 22:56 UTC
    I don't know how what you describe works in cryptology, but that's definitely the vibe here. Something like an intersection of a series of "hashes". The art here is to find out the method of building them.
[reply]
      > Something like an intersection of a series of "hashes".

      It would help to know for which reason.

      There is no way this will be more performant than a direct download.

      Anyway anything which will work "your way" on a string will also work on a serialized hash. Just use Data::Dumper to get your string.

      Cheers Rolf
      (addicted to the Perl Programming Language :)
      Wikisyntax for the Monastery

[reply]
        I am completely unable to guess, why you even mention direct download. The question wants to limit the download link. That's all. If you can spare 1 bit of data on that link, it counts as more performant, because that's how performance is counted in this case, per problem definition. Yes, it is so simple. For each such spared downlink bit cost can be counted in terms of extra uplink transfer and computation on the client and/or the server. So simple. And the "hash" you took the wrong direction. The point of any such "hashing" would be to decrease the exchange rate between spared bytes on the downlink and the cost on the uplink. I have an answer to this mystery already and will post it in a moment in bliako's subthread (the one with script code).
[reply]

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