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A Feistel network is a way of constructing an invertible permutation from a (possibly non-invertible) function. If the function used is pseudorandom and has a large domain, then 3-4 rounds yields a pseudorandom permutation (3 rounds suffice if the adversary can only ask "compute" queries, and 4 rounds are needed if the adversary can ask "invert" queries). ...


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Alright, so using per-round validation in almost all cases causes a decrease in performance. Simple probability tells us that after each round, there is a 1/x chance that the round will fall within the "valid" data set. This means that for any cycle through a Feistel network, the output has this 1/x chance of being correct. Likewise, any Feistel network ...


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I don't think this would break correctness, but it's possible you might actually slow your algorithm down on average. You'd need a more rigorous combinatorial analysis of the expected number of repeated rounds vs. the expected number of full cycle walks. That really depends on the specific algorithm; are you using FFX? You'd also need to show that doing ...



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