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this post was submitted on 22 Dec 2023
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Cybersecurity
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If A can run this program at will and it determines the minimum value, it's O(log(n)) to determine what B is, even with perfect encryption, by using arbitrary values of A.
INT X = MAX INT PREV_X = 0 BOOL B_IS_MIN = True
While (X != PREV_X){
PREV_X = X B_IS_MIN = Encrypted_Min(X,B)
If(B_IS_MIN), X = X/2 If(!B_IS_MIN), X = X*1.5
}
Unless I've made a typo, this psuedocode will step to B in log time, and will break the while loop once it's found, even if the user has no way to know the value of B besides the minimum.
Indeed, I didn't think of that. And would it be possible to allow only one check and destroy/make the information of B unusable after this check?
Thank you for your reply!
With some more restrictions, you may want to look into oblivious transfer https://yewtu.be/watch?v=wE5cl8J27Is
that's interesting indeed! thank you very much!