  A major open problem in computational complexity is the existence of a
one-way function, namely a function from strings to strings which is
computationally easy to compute but hard to invert. Levin (2023) formulated the
notion of one-way functions from reals (infinite bit-sequences) to reals in
terms of computability, and asked whether partial computable one-way functions
exist. We give a strong positive answer using the hardness of the halting
problem and exhibiting a total computable one-way function.
