hi , if u r an encryption expert ,help me with this ?

I have a secret 5 bit long password K. If I disclose a value K’ such that K’ = f(K) for a public non-invertible function f that takes an arbitrary long number and outputs a fixed length (say, 1,000 bits in length) number. Is it possible (given a reasonably powerful computer) for you to determine K, if you are given K’, f and the length of K? If so, how many calls to f do you need to make on average? What about if K is 56 bits long? What if it is 128 bits long?

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