It's hard to say. I did not read the whole thing, but red flags were glaring. I don't have anything against the author. In fact, I, myself, have implemented poo

It's hard to say. I did not read the whole thing, but red flags were glaring. I don't have anything against the author. In fact, I, myself, have implemented poor crypto based on (various levels at various times of) understanding it and later realized I didn't know nearly enough about it. For that reason, honestly, my suggestion is stop looking for a fix to this guide and study up basic crypto concepts from scratch from a proper source (like the one I mentioned) and then try to find a good library that does it in your favorite language. Understand what the library does first and let it do it on your behalf.