I think it mostly depends on purpose. Crypto is being reinvented several times a day by students needing to understand the mechanics of various algorithms. Per

I think it mostly depends on purpose. Crypto is being reinvented several times a day by students needing to understand the mechanics of various algorithms. Personally, I find it rewarding to reimplement something known. There is always a solution when you are stuck, and who knows. Maybe one will develop a better API for the system of something else.