There is an explanation of math behind the RSA on: What is the relation between RSA & Fermat's little theorem? It is answered by Antony Vennard. It looks very interesting, but unfortunately Antony is not defining many of the terms. I would like to have a place where I can ask additional questions regarding Antony's answer and get clarification from either him, or anyone else who knows the subject.
I wrote my question in the answer field, and it was deleted. But I could not find a field or asking related questions.
I don't want to ask a new question, because my question is about the existing answer. For example I'd like to know how the definition of ϕ(p,q). He is only defining ϕ(p), but not ϕ of a set of a pair of numbers. This is just one example.
Ideally I'd like to see the explanation with examples of concrete numbers used, and how it relates to cryptography.