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I am still not very familiar with this kind of proofs, but from what I understood: 1) This inclusion is actually a condition which defines in itself what a hiding key is. That is to say that this paragraph does not say that the inclusion is ensured, but that we should make sure that it is, if we want a perfectly hiding key. However, you may find sets of ...


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There is quite a bit of confusion in your question. First, differentiate between the real and ideal models. The adversary in the ideal model sends the adversary's input and gets its output (and can also sometimes determine if the honest party gets output, depending on the model). We often call the ideal adversary a "simulator" since this is how we build the ...


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The objective of the simulator is to make the simulated world (often called the ideal world) indistinguishable from the real world (running the actual protocol). See my write-up on the UC framework here for more detail. In the proof setup, the entity attempting to distinguish between the two worlds is often assumed to provide the inputs to the parties. That ...


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$SIM_s$ can do that, but it doesn't need to. $\:$ The distinguisher chooses the parties' inputs.


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The simplest example I know of is actually for a pathological case. Namely, it is presented in Chapter 2 of the book of Hazay and Lindell as an example of a two-party MPC protocol which is secure against a malicious adversary but not against a semi-honest one (in the classical sense, for this reason they prefer the notion of augmented semi-honest ...


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They both symmetrical encrypt their keys by itself in an algorithm (or aes with enough iterations) that it takes minutes, even hours to complete (this gives ek1). Then they will do the same thing again (encrypt ek1 by itself) (this gives ek2) and send ek2 to the other person when they both say they are done. If they don't align, both parties then send ek1 to ...


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If its possible that either of the party can get hold of the other's cipher text during transmission and decode it, then they could use that itself for determining if they can decode each-other's messages. Since either of the party can use a random-key thinking the other person will be using the real one, the effectiveness of this technique would be the ...


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I'm new here so I'm not sure about the best way to hold this discussion. So, I am adding a different answer to relate to why my proof sketch showing the impossibility of the problem in this question, versus Ricky's proof above that the protocol in this paper (page 16) is impossible. The answer is very connected to technical details to how you define and ...


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This cannot be done. It is provably impossible. In order to explain this in technical terms, what you are looking for is a FAIR protocol to compute equality of long random strings (I added the latter since it adds a constraint and so in theory could make it easier). In any case, if I had such a protocol, then I could toss a fair unbiased coin. Here is the ...


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Answering the question in your title (and not addressing your proposed alternative which I don't quite understand) there is a zero knowledge proof of password protocol "SRP" which is fast and effective. SRP does not seem to have been given as wide publicity as it should get. Having implemented it, and being an advocate of its use, I don't really understand ...



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