Score:0

Is it One Way Function?

ba flag

I am currently studying a course in cryptography, and I have this exercise about OWF. enter image description here

enter image description here

I'm failing to prove that this is an inverter to f. Am I in the right direction at all? Thank you!

Score:0
hk flag

Assume $g$ is not an OWF. What does it mean for $g$? How can this knowledge about $g$ help You find a preimage of $f$? What does it mean about $f$ being OWP?

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ch flag

What is the probability that the $x$ you got ( from your reduction ) is the correct pre-image of $y$ with $f$? I.e., $\Pr[f^{-1}(y) = x]$?

Niv Peretz avatar
ba flag
i thought its 1/2 but lets say n= 100. assume all permutations of {0,1}^n such that they contain 5 zeros are mapped to 1111100000. also assume f(1111110000)=1111100001 (6 4 zeros). now if (g^-1)(111110000) = 1111110000 then f^-1 is right at only one out of about 250 times.
Niv Peretz avatar
ba flag
I get it that that cannot be a one-way permutation but I can't prove it formally
Niv Peretz avatar
ba flag
let's say n=10 *
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