"How does someone go about making a one way function" It's hard -- cryptographers have yet to even prove that one way functions actually exist! We have lots o

"How does someone go about making a one way function" It's hard -- cryptographers have yet to even prove that one way functions actually exist! We have lots of theoretical candidates -- discrete logarithms for certain groups, integer factorization, problems related to hidden linear codes, and so forth. Some day, we will either prove that OWFs do not exist, or that OWFs do exist (and hopefully one of the candidates is actually an OWF), or that the existence or non-existence of OWFs is independent of the mathematical systems we use right now (i.e. that it is an axiom). Having said that, you might be interested in the work of Atjai and Dwork on creating an OWF (a trapdoor OWF, actually, and a corresponding public key cryptosystem) from an NP-Hard problem: https://dl.acm.org/citation.cfm?id=258604 https://dl.acm.org/citation.cfm?id=258604